The Eighteenth Century

In so far as the intellectual climates of different epochs can be contrasted, the eighteenth century in Europe was the complete antithesis to the Middle Ages. The contrast is symbolised by the difference between the cathedral of Chartres and the Parisian salons, where D’Alembert conversed with Voltaire. The Middle Ages were haunted with the desire to rationalise the infinite: the men of the eighteenth century rationalised the social life of modern communities, and based their sociological theories on an appeal to the facts of nature. The earlier period was the age of faith, based upon reason. In the later period, they let sleeping dogs lie: it was the age of reason, based upon faith. To illustrate my meaning:—St. Anselm would have been distressed if he had failed to find a convincing argument for the existence of God, and on this argument he based his edifice of faith, whereas Hume based his Dissertation on the Natural History of Religion upon his faith in the order of nature. In comparing these epochs it is well to remember that reason can err, and that faith may be misplaced.

As far as we can compare the intellectual climates of different eras, eighteenth-century Europe was the complete opposite of the Middle Ages. The contrast is symbolized by the difference between the cathedral of Chartres and the Parisian salons where D’Alembert conversed with Voltaire. The Middle Ages were preoccupied with the desire to rationalize the infinite. The men of the eighteenth century rationalized the social life of modern communities. They based their theories of society on an appeal to the facts of nature. The earlier period was the age of faith, based on reason. In the later period, people let sleeping dogs lie. It was the age of reason, based on faith. To illustrate what I mean, St. Anselm would have been distressed if he had failed to find a convincing argument for the existence of God. He built his system of faith on that argument. Hume, by contrast, based his Dissertation on the Natural History of Religion on his faith in the order of nature. In comparing these eras, it is worth remembering that reason can err and faith may be misplaced.

In my previous lecture I traced the evolution, during the seventeenth century, of the scheme of scientific ideas which has dominated thought ever since. It involves a fundamental duality, with material on the one hand, and on the other hand mind. In between there lie the concepts of life, organism, function, instantaneous reality, interaction, order of nature, which collectively form the Achilles heel of the whole system.

In my previous lecture, I traced the development of a system of scientific ideas during the seventeenth century. This system has dominated thought ever since. It rests on a fundamental division between material on one hand and mind on the other. Between them lie the concepts of life, organism, function, instantaneous reality, interaction, and the order of nature. Together, these concepts form the Achilles heel of the whole system.

I also expressed my conviction that if we desired to obtain a more fundamental expression of the concrete character of natural fact, the element in this scheme which we should first criticise is the concept of simple location. In view therefore of the importance which this idea will assume in these lectures, I will repeat the meaning which I have attached to this phrase. To say that a bit of matter has simple location means that, in expressing its spatio-temporal relations, it is adequate to state that it is where it is, in a definite finite region of space, and throughout a definite finite duration of time, apart from any essential reference of the relations of that bit of matter to other regions of space and to other durations of time. Again, this concept of simple location is independent of the controversy between the absolutist and the relativist views of space or of time. So long as any theory of space, or of time, can give a meaning, either absolute or relative, to the idea of a definite region of space, and of a definite duration of time, the idea of simple location has a perfectly definite meaning. This idea is the very foundation of the seventeenth century scheme of nature. Apart from it, the scheme is incapable of expression. I shall argue that among the primary elements of nature as apprehended in our immediate experience, there is no element whatever which possesses this character of simple location. It does not follow, however, that the science of the seventeenth century was simply wrong. I hold that by a process of constructive abstraction we can arrive at abstractions which are the simply-located bits of material, and at other abstractions which are the minds included in the scientific scheme. Accordingly, the real error is an example of what I have termed: The Fallacy of Misplaced Concreteness.

I also said that, if we want a more fundamental account of the concrete character of natural facts, we should first examine one element of this scheme critically: the concept of simple location. Since this idea will be important in these lectures, I will repeat what I mean by the phrase. To say that a bit of matter has simple location means that, to describe its relations in space and time, it is enough to state where and when it is. It is in a definite, finite region of space throughout a definite, finite period of time. This account need not refer in any essential way to the bit of matter’s relations to other regions of space or other periods of time. The concept of simple location is also independent of the dispute between absolutist and relativist views of space or time. A theory of space or time may give either an absolute or a relative meaning to a definite region of space or a definite period of time. As long as it can do so, the idea of simple location has a perfectly definite meaning. Simple location is the very foundation of the seventeenth century scheme of nature. Without it, the scheme cannot be expressed. I shall argue that none of the primary elements of nature, as we apprehend them in our immediate experience, has this character of simple location. But this does not mean that seventeenth century science was simply wrong. I hold that, through a process of constructive abstraction, we can arrive at abstractions that are the simply located bits of material. We can also arrive at other abstractions that are the minds included in the scientific scheme. The real error, then, is an example of what I have called the Fallacy of Misplaced Concreteness.

The advantage of confining attention to a definite group of abstractions, is that you confine your thoughts to clear-cut definite things, with clear-cut definite relations. Accordingly, if you have a logical head, you can deduce a variety of conclusions respecting the relationships between these abstract entities. Furthermore, if the abstractions are well-founded, that is to say, if they do not abstract from everything that is important in experience, the scientific thought which confines itself to these abstractions will arrive at a variety of important truths relating to our experience of nature. We all know those clear-cut trenchant intellects, immovably encased in a hard shell of abstractions. They hold you to their abstractions by the sheer grip of personality.

The advantage of focusing on a particular group of abstractions is that you can think about clear, definite things with clear, definite relationships. So, if you have a logical mind, you can draw many conclusions about the relationships between these abstract entities. And if the abstractions are well-founded, scientific thought focused on them will arrive at many important truths about our experience of nature. By well-founded, I mean that the abstractions do not leave out everything important in experience. We all know those sharp, clear-cut intellects, firmly enclosed in a hard shell of abstractions. They hold you to their abstractions through the sheer force of personality.

The disadvantage of exclusive attention to a group of abstractions, however well-founded, is that, by the nature of the case, you have abstracted from the remainder of things. In so far as the excluded things are important in your experience, your modes of thought are not fitted to deal with them. You cannot think without abstractions; accordingly, it is of the utmost importance to be vigilant in critically revising your modes of abstraction. It is here that philosophy finds its niche as essential to the healthy progress of society. It is the critic of abstractions. A civilisation which cannot burst through its current abstractions is doomed to sterility after a very limited period of progress. An active school of philosophy is quite as important for the locomotion of ideas, as is an active school of railway engineers for the locomotion of fuel.

The disadvantage of focusing exclusively on a group of abstractions, however sound, is that you necessarily leave everything else out. To the extent that these excluded things matter in your experience, your ways of thinking are not suited to dealing with them. You cannot think without abstractions. So it is extremely important to keep critically examining and revising your ways of making abstractions. This is where philosophy has an essential role in the healthy progress of society. It criticizes abstractions. A civilization that cannot break through its current abstractions is doomed to stagnate after a very limited period of progress. An active school of philosophy is just as important for moving ideas as an active school of railway engineers is for moving fuel.

Sometimes it happens that the service rendered by philosophy is entirely obscured by the astonishing success of a scheme of abstractions in expressing the dominant interests of an epoch. This is exactly what happened during the eighteenth century. Les philosophes were not philosophers. They were men of genius, clear-headed and acute, who applied the seventeenth century group of scientific abstractions to the analysis of the unbounded universe. Their triumph, in respect to the circle of ideas mainly interesting to their contemporaries, was overwhelming. Whatever did not fit into their scheme was ignored, derided, disbelieved. Their hatred of Gothic architecture symbolises their lack of sympathy with dim perspectives. It was the age of reason, healthy, manly, upstanding reason; but, of one-eyed reason, deficient in its vision of depth. We cannot overrate the debt of gratitude which we owe to these men. For a thousand years Europe had been a prey to intolerant, intolerable visionaries. The common sense of the eighteenth century, its grasp of the obvious facts of human suffering, and of the obvious demands of human nature, acted on the world like a bath of moral cleansing. Voltaire must have the credit, that he hated injustice, he hated cruelty, he hated senseless repression, and he hated hocus-pocus. Furthermore, when he saw them, he knew them. In these supreme virtues, he was typical of his century, on its better side. But if men cannot live on bread alone, still less can they do so on disinfectants. The age had its limitations; yet we cannot understand the passion with which some of its main positions are still defended, especially in the schools of science, unless we do full justice to its positive achievements. The seventeenth century scheme of concepts was proving a perfect instrument for research.

Sometimes a set of abstract ideas succeeds so brilliantly in expressing an age’s main interests that it completely obscures the value of philosophy. This is exactly what happened during the eighteenth century. Les philosophes were not philosophers. They were brilliant, clearheaded, and perceptive men. They applied the seventeenth century’s scientific abstractions to the analysis of the boundless universe. They achieved an overwhelming triumph in explaining the ideas that most interested their contemporaries. They ignored, ridiculed, or disbelieved whatever did not fit their scheme. Their hatred of Gothic architecture symbolizes their lack of sympathy for dim perspectives. It was the age of reason, healthy, manly, upright reason. But its reason was one-eyed, lacking depth of vision. We cannot overstate the debt of gratitude we owe these men. For a thousand years Europe had been at the mercy of intolerant, intolerable visionaries. Eighteenth-century common sense acted on the world like a bath that washed it clean morally. It recognized the obvious facts of human suffering and the obvious demands of human nature. Voltaire deserves credit for hating injustice, cruelty, senseless repression, and hocus-pocus. What is more, he recognized them when he saw them. In these supreme virtues, he represented the better side of his century. But if people cannot live on bread alone, they can live even less on disinfectants. The age had its limitations. Yet we must fully recognize its positive achievements to understand the passion with which some of its main positions are still defended, especially in the sciences. The seventeenth century’s set of concepts was proving a perfect tool for research.

This triumph of materialism was chiefly in the sciences of rational dynamics, physics, and chemistry. So far as dynamics and physics were concerned, progress was in the form of direct developments of the main ideas of the previous epoch. Nothing fundamentally new was introduced, but there was an immense detailed development. Special case after special case was unravelled. It was as though the very Heavens were being opened, on a set plan. In the second half of the century, Lavoisier practically founded chemistry on its present basis. He introduced into it the principle that no material is lost or gained in any chemical transformations. This was the last success of materialistic thought, which has not ultimately proved to be double-edged. Chemical science now only waited for the atomic theory, in the next century.

This triumph of materialism took place chiefly in rational dynamics, physics, and chemistry. In dynamics and physics, progress came through direct developments of the main ideas of the previous era. Nothing fundamentally new was introduced, but the details were developed immensely. One special case after another was worked out. It was as though the heavens themselves were being opened according to a plan. In the second half of the century, Lavoisier practically founded chemistry on its present basis. He introduced the principle that no material is lost or gained in any chemical transformation. This was the last success of materialistic thought that has not ultimately proved double-edged. Chemical science now only had to wait for the atomic theory in the next century.

In this century the notion of the mechanical explanation of all the processes of nature finally hardened into a dogma of science. The notion won through on its merits by reason of an almost miraculous series of triumphs achieved by the mathematical physicists, culminating in the Méchanique Analytique of Lagrange, which was published in 1787. Newton’s Principia was published in 1687, so that exactly one hundred years separates the two great books. This century contains the first period of mathematical physics of the modern type. The publication of Clerk Maxwell’s Electricity and Magnetism in 1873 marks the close of the second period. Each of these three books introduces new horizons of thought affecting everything which comes after them.

In this century, the idea that mechanical processes explain all of nature finally became a scientific dogma. The idea prevailed on its merits, thanks to an almost miraculous series of triumphs by mathematical physicists. These triumphs culminated in Lagrange’s Méchanique Analytique, published in 1787. Newton’s Principia was published in 1687, so exactly one hundred years separate the two great books. This century contains the first period of modern mathematical physics. The publication of Clerk Maxwell’s Electricity and Magnetism in 1873 marks the end of the second period. Each of these three books opens up new horizons of thought that affect everything that follows.

In considering the various topics to which mankind has bent its systematic thought, it is impossible not to be struck with the unequal distribution of ability among the different fields. In almost all subjects there are a few outstanding names. For it requires genius to create a subject as a distinct topic for thought. But in the case of many topics, after a good beginning very relevant to its immediate occasion, the subsequent development appears as a weak series of flounderings, so that the whole subject gradually loses its grip on the evolution of thought. It was far otherwise with mathematical physics. The more you study this subject, the more you will find yourself astonished by the almost incredible triumphs of intellect which it exhibits. The great mathematical physicists of the eighteenth and first few years of the nineteenth century, most of them French, are a case in point: Maupertuis, Clairaut, D’Alembert, Lagrange, Laplace, Fourier, form a series of names, such that each recalls to mind some achievement of the first rank. When Carlyle, as the mouthpiece of the subsequent Romantic Age, scoffingly terms the period the Age of Victorious Analysis, and mocks at Maupertuis as a ‘sublimish gentleman in a white periwig,’ he only exhibits the narrow side of the Romanticists whom he is then voicing.

When we consider the subjects people have studied systematically, we cannot help noticing how unevenly talent is distributed among them. Almost every subject has a few outstanding names. That is because it takes genius to establish a subject as a distinct field of thought. But many subjects begin well, with work highly relevant to the immediate occasion, then go through a weak series of struggles. As a result, the subject gradually loses its influence on the development of thought. Mathematical physics was very different. The more you study it, the more astonished you will be by its almost unbelievable intellectual triumphs. Consider the great mathematical physicists of the eighteenth century and the first few years of the nineteenth, most of them French. Maupertuis, Clairaut, D’Alembert, Lagrange, Laplace, Fourier: each name brings to mind an achievement of the highest rank. Carlyle, speaking for the Romantic Age that followed, mockingly calls the period the Age of Victorious Analysis. He also mocks Maupertuis as a ‘sublimish gentleman in a white periwig.’ In doing so, he reveals only the narrow side of the Romanticists for whom he speaks.

It is impossible to explain intelligently, in a short time and without technicalities, the details of the progress made by this school. I will, however, endeavour to explain the main point of a joint achievement of Maupertuis and Lagrange. Their results, in conjunction with some subsequent mathematical methods due to two great German mathematicians of the first half of the nineteenth century, Gauss and Riemann, have recently proved themselves to be the preparatory work necessary for the new ideas which Herz and Einstein have introduced into mathematical physics. Also they inspired some of the best ideas in Clerk Maxwell’s treatise, already mentioned in this lecture.

It is impossible to explain the details of this school’s progress clearly in a short time without using technical terms. However, I will try to explain the main point of a joint achievement by Maupertuis and Lagrange. Their results, together with later mathematical methods developed by Gauss and Riemann, have recently proved essential groundwork. Gauss and Riemann were two great German mathematicians of the first half of the nineteenth century. Their work helped prepare the way for the new ideas that Herz and Einstein have introduced into mathematical physics. The work of Maupertuis and Lagrange also inspired some of the best ideas in Clerk Maxwell’s treatise, mentioned earlier in this lecture.

They aimed at discovering something more fundamental and more general than Newton’s laws of motion which were discussed in the previous lecture. They wanted to find some wider ideas, and in the case of Lagrange some more general means of mathematical exposition. It was an ambitious enterprise, and they were completely successful. Maupertuis lived in the first half of the eighteenth century, and Lagrange’s active life lay in its second half. We find in Maupertuis a tinge of the theologic age which preceded his birth. He started with the idea that the whole path of a material particle between any limits of time must achieve some perfection worthy of the providence of God. There are two points of interest in this motive principle. In the first place, it illustrates the thesis which I was urging in my first lecture that the way in which the medieval church had impressed on Europe the notion of the detailed providence of a rational personal God was one of the factors by which the trust in the order of nature had been generated. In the second place, though we are now all convinced that such modes of thought are of no direct use in detailed scientific enquiry, Maupertuis’ success in this particular case shows that almost any idea which jogs you out of your current abstractions may be better than nothing. In the present case what the idea in question did for Maupertuis was to lead him to enquire what general property of the path as a whole could be deduced from Newton’s laws of motion. Undoubtedly this was a very sensible procedure whatever one’s theological notions. Also his general idea led him to conceive that the property found would be a quantitative sum, such that any slight deviation from the path would increase it. In this supposition he was generalising Newton’s first law of motion. For an isolated particle takes the shortest route with uniform velocity. So Maupertuis conjectured that a particle travelling through a field of force would realise the least possible amount of some quantity. He discovered such a quantity and called it the integral action between the time limits considered. In modern phraseology it is the sum through successive small lapses of time of the difference between the kinetic and potential energies of the particle at each successive instant. This action, therefore, has to do with the interchange between the energy arising from motion and the energy arising from position. Maupertuis had discovered the famous theorem of least action. Maupertuis was not quite of the first rank in comparison with such a man as Lagrange. In his hands and in those of his immediate successors, his principle did not assume any dominating importance. Lagrange put the same question on a wider basis so as to make its answer relevant to actual procedure in the development of dynamics. His Principle of Virtual Work as applied to systems in motion is in effect Maupertuis’ principle conceived as applying at each instant of the path of the system. But Lagrange saw further than Maupertuis. He grasped that he had gained a method of stating dynamical truths in a way which is perfectly indifferent to the particular methods of measurement employed in fixing the positions of the various parts of the system. Accordingly, he went on to deduce equations of motion which are equally applicable whatever quantitative measurements have been made, provided that they are adequate to fix positions. The beauty and almost divine simplicity of these equations is such that these formulae are worthy to rank with those mysterious symbols which in ancient times were held directly to indicate the Supreme Reason at the base of all things. Later Herz—inventor of electromagnetic waves—based mechanics on the idea of every particle traversing the shortest path open to it under the circumstances constraining its motion; and finally Einstein, by the use of the geometrical theories of Gauss and Riemann, showed that these circumstances could be construed as being inherent in the character of space-time itself. Such, in barest outline, is the story of dynamics from Galileo to Einstein.

They aimed to discover something more fundamental and general than Newton’s laws of motion, discussed in the previous lecture. They wanted to find broader ideas. Lagrange also wanted more general ways of expressing those ideas mathematically. It was an ambitious undertaking, and they succeeded completely. Maupertuis lived in the first half of the eighteenth century. Lagrange’s active life fell in the second half. In Maupertuis we find a trace of the theological age before his birth. He began with an idea about the complete path a material particle takes between any two points in time. He believed that path must achieve a perfection worthy of God’s providence. Two things are interesting about this guiding idea. First, it illustrates a point I argued in my first lecture. The medieval church impressed on Europe the idea of a rational, personal God whose providence governed every detail. That idea was one of the factors that fostered trust in the order of nature. Second, we are now all convinced that such ways of thinking are of no direct use in detailed scientific inquiry. Even so, Maupertuis’ success in this case shows that almost any idea may be better than nothing if it jolts you out of your current abstractions. In this case, the idea led Maupertuis to ask a question. What general property of the path as a whole could be deduced from Newton’s laws of motion? That was certainly a sensible approach, whatever one’s theological beliefs. His general idea also led him to think the property would be a quantitative sum. Any slight deviation from the path would increase this sum. In making this assumption, he was generalizing Newton’s first law of motion. An isolated particle takes the shortest route at a uniform velocity. So Maupertuis conjectured that a particle traveling through a field of force would produce the least possible amount of some quantity. He discovered such a quantity and called it the integral action between the two times considered. In modern terms, it is calculated by adding up the differences between the particle’s kinetic and potential energies over successive short intervals. The difference is measured at each successive instant. This action therefore concerns the interchange between energy arising from motion and energy arising from position. Maupertuis had discovered the famous theorem of least action. Maupertuis was not quite of the first rank compared with a man like Lagrange. In the hands of Maupertuis and his immediate successors, his principle did not become especially important. Lagrange put the same question on a broader basis. This made the answer relevant to the actual methods used to develop dynamics. His Principle of Virtual Work, as applied to systems in motion, is essentially Maupertuis’ principle applied at each instant along the system’s path. But Lagrange saw further than Maupertuis. He understood that he had found a way to state truths about dynamics that did not depend on the particular measurements used to locate the system’s parts. He therefore went on to derive equations of motion that apply equally whatever quantitative measurements are used, provided they are adequate to fix positions. These equations have a beauty and an almost divine simplicity. Their formulas deserve to rank with the mysterious symbols that people in ancient times believed directly indicated the Supreme Reason underlying all things. Later, Herz, the inventor of electromagnetic waves, based mechanics on an idea about the path of every particle. Each particle, he held, takes the shortest path open to it under the circumstances that constrain its motion. Finally, Einstein used the geometrical theories of Gauss and Riemann to show that these circumstances could be understood as inherent in the character of space-time itself. Such, in the barest outline, is the story of dynamics from Galileo to Einstein.

Meanwhile Galvani and Volta lived and made their electric discoveries; and the biological sciences slowly gathered their material, but still waited for dominating ideas. Psychology, also, was beginning to disengage itself from its dependence on general philosophy. This independent growth of psychology was the ultimate result of its invocation by John Locke as a critic of metaphysical licence. All the sciences dealing with life were still in an elementary observational stage, in which classification and direct description were dominant. So far the scheme of abstractions was adequate to the occasion.

Meanwhile, Galvani and Volta lived and made their electrical discoveries. The biological sciences were slowly gathering material, but they still lacked guiding ideas. Psychology, too, was beginning to separate itself from general philosophy. This independent growth was the eventual result of John Locke’s appeal to psychology to criticize unchecked metaphysical speculation. All the sciences concerned with life were still at an early observational stage, dominated by classification and direct description. So far, the scheme of abstractions was adequate for the task.

In the realm of practice, the age which produced enlightened rulers, such as the Emperor Joseph of the House of Hapsburg, Frederick the Great, Walpole, the great Lord Chatham, George Washington, cannot be said to have failed. Especially when to these rulers, it adds the invention of parliamentary cabinet government in England, of federal presidential government in the United States, and of the humanitarian principles of the French Revolution. Also in technology it produced the steam-engine, and thereby ushered in a new era of civilisation. Undoubtedly, as a practical age the eighteenth century was a success. If you had asked one of the wisest and most typical of its ancestors, who just saw its commencement, I mean John Locke, what he expected from it, he would hardly have pitched his hopes higher than its actual achievements.

In practical affairs, the age that produced enlightened rulers cannot be called a failure. These included Emperor Joseph of the House of Hapsburg, Frederick the Great, Walpole, the great Lord Chatham, and George Washington. The age also invented parliamentary cabinet government in England, federal presidential government in the United States, and the humanitarian principles of the French Revolution. In technology, it produced the steam engine and thereby began a new era of civilization. Without doubt, the eighteenth century was a practical success. John Locke was one of the wisest and most typical figures of the preceding age, and he lived to see the eighteenth century begin. If you had asked him what he expected from it, he would hardly have hoped for more than it actually achieved.

In developing a criticism of the scientific scheme of the eighteenth century, I must first give my main reason for ignoring nineteenth century idealism—I am speaking of the philosophic idealism which finds the ultimate meaning of reality in mentality that is fully cognitive. This idealistic school, as hitherto developed, has been too much divorced from the scientific outlook. It has swallowed the scientific scheme in its entirety as being the only rendering of the facts of nature, and has then explained it as being an idea in the ultimate mentality. In the case of absolute idealism, the world of nature is just one of the ideas, somehow differentiating the unity of the Absolute: in the case of pluralistic idealism involving monadic mentalities, this world is the greatest common measure of the various ideas which differentiate the various mental unities of the various monads. But, however you take it, these idealistic schools have conspicuously failed to connect, in any organic fashion, the fact of nature with their idealistic philosophies. So far as concerns what will be said in these lectures, your ultimate outlook may be realistic or idealistic. My point is that a further stage of provisional realism is required in which the scientific scheme is recast, and founded upon the ultimate concept of organism.

In developing a criticism of the eighteenth-century scientific scheme, I must first explain why I am ignoring nineteenth-century idealism. I mean the philosophical idealism that finds the ultimate meaning of reality in a mind that fully knows. As developed so far, this school of idealism has been too far removed from the scientific outlook. It has accepted the entire scientific scheme as the only account of the facts of nature. It has then explained that scheme as an idea in the ultimate mind. For absolute idealism, the natural world is just one of the ideas that somehow distinguishes elements within the unity of the Absolute. For pluralistic idealism involving monadic minds, the natural world is the greatest common measure of the various ideas that distinguish the mental unities of the various monads. But in either case, these schools of idealism have clearly failed to connect the facts of nature with their philosophies in any organic way. As far as these lectures are concerned, your ultimate outlook may be realistic or idealistic. My point is that we need a further stage of provisional realism. At that stage, the scientific scheme must be recast and founded on the ultimate concept of organism.

In outline, my procedure is to start from the analysis of the status of space and of time, or in modern phraseology, the status of space-time. There are two characters of either. Things are separated by space, and are separated by time: but they are also together in space, and together in time, even if they be not contemporaneous. I will call these characters the ‘separative’ and the ‘prehensive’ characters of space-time. There is yet a third character of space-time. Everything which is in space receives a definite limitation of some sort, so that in a sense it has just that shape which it does have and no other, also in some sense it is just in this place and in no other. Analogously for time, a thing endures during a certain period, and through no other period. I will call this the ‘modal’ character of space-time. It is evident that the modal character taken by itself gives rise to the idea of simple location. But it must be conjoined with the separative and prehensive characters.

In outline, I begin by analyzing the status of space and time, or, in modern terms, space-time. Both space and time have two characteristics. Things are separated by space and by time. But they are also together in space and together in time, even if they do not exist at the same time. I call these the ‘separative’ and ‘prehensive’ characteristics of space-time. Space-time has a third characteristic. Everything in space has a definite limit of some kind. So, in a sense, it has exactly the shape it has and no other. Also, in some sense, it is in exactly this place and no other. Similarly, in time, a thing lasts for a certain period and no other. I call this the ‘modal’ characteristic of space-time. Clearly, the modal characteristic alone gives rise to the idea of simple location. But it must be considered together with the separative and prehensive characteristics.

For simplicity of thought, I will first speak of space only, and will afterwards extend the same treatment to time.

To keep things simple, I will first discuss space alone. Later, I will apply the same approach to time.

The volume is the most concrete element of space. But the separative character of space, analyses a volume into sub-volumes, and so on indefinitely. Accordingly, taking the separative character in isolation, we should infer that a volume is a mere multiplicity of non-voluminous elements, of points in fact. But it is the unity of volume which is the ultimate fact of experience, for example, the voluminous space of this hall. This hall as a mere multiplicity of points is a construction of the logical imagination.

A volume is the most concrete element of space. But space can be divided, so a volume can be divided into smaller volumes, and those into still smaller ones, indefinitely. If we consider this divisibility alone, we would conclude that a volume is merely a collection of elements without volume, namely points. But the unity of a volume is the ultimate fact of experience. Consider, for example, the space this hall occupies. To see this hall as merely a collection of points is a construction of the logical imagination.

Accordingly, the prime fact is the prehensive unity of volume, and this unity is mitigated or limited by the separated unities of the innumerable contained parts. We have a prehensive unity, which is yet held apart as an aggregate of contained parts. But the prehensive unity of the volume is not the unity of a mere logical aggregate of parts. The parts form an ordered aggregate, in the sense that each part is something from the standpoint of every other part, and also from the same standpoint every other part is something in relation to it. Thus if A and B and C are volumes of space, B has an aspect from the standpoint of A, and so has C, and so has the relationship of B and C. This aspect of B from A is of the essence of A. The volumes of space have no independent existence. They are only entities as within the totality; you cannot extract them from their environment without destruction of their very essence. Accordingly, I will say that the aspect of B from A is the mode in which B enters into the composition of A. This is the modal character of space, that the prehensive unity of A is the prehension into unity of the aspects of all other volumes from the standpoint of A. The shape of a volume is the formula from which the totality of its aspects can be derived. Thus the shape of a volume is more abstract than its aspects. It is evident that I can use Leibniz’s language, and say that every volume mirrors in itself every other volume in space.

The primary fact, then, is the prehensive unity of a volume. This unity is limited by the separate unities of the countless parts within it. The volume has a prehensive unity, yet it remains a collection of separate parts. But its prehensive unity is not simply the unity of a logical collection of parts. The parts form an ordered collection. Each part is something from the standpoint of every other part. From that same standpoint, every other part is also something in relation to it. For example, suppose A, B, and C are volumes of space. B has an aspect from the standpoint of A, and so does C. The relationship between B and C also has an aspect from A’s standpoint. This aspect of B from A’s standpoint is essential to A. Volumes of space have no independent existence. They exist as entities only within the whole. You cannot remove them from their surroundings without destroying their very essence. So I will say that the aspect of B from A’s standpoint is the mode in which B enters into A’s composition. Space has a modal character. The prehensive unity of A brings together the aspects of all other volumes from A’s standpoint. The shape of a volume is the formula from which all its aspects can be derived. So the shape of a volume is more abstract than its aspects. Clearly, I can use Leibniz’s language and say that every volume mirrors within itself every other volume in space.

Exactly analogous considerations hold with respect to durations in time. An instant of time, without duration, is an imaginative logical construction. Also each duration of time mirrors in itself all temporal durations.

Exactly the same considerations apply to periods of time. An instant with no duration is a logical construct of the imagination. Also, each period of time reflects all periods of time within itself.

But in two ways I have introduced a false simplicity. In the first place, I should have conjoined space and time, and conducted my explanation in respect to four-dimensional regions of space-time. I have nothing to add in the way of explanation. In your minds, substitute such four-dimensional regions for the spatial volumes of the previous explanations.

But I have made things seem simpler than they are in two ways. First, I should have combined space and time. I should have explained the subject in terms of four-dimensional regions of space-time. I have nothing more to add by way of explanation. In your minds, replace the spatial volumes in my earlier explanations with these four-dimensional regions.

Secondly, my explanation has involved itself in a vicious circle. For I have made the prehensive unity of the region A to consist of the prehensive unification of the modal presences in A of other regions. This difficulty arises because space-time cannot in reality be considered as a self-subsistent entity. It is an abstraction, and its explanation requires reference to that from which it has been extracted. Space-time is the specification of certain general characters of events and of their mutual ordering. This recurrence to concrete fact brings me back to the eighteenth century, and indeed to Francis Bacon in the seventeenth century. We have to consider the development in those epochs, of the criticism of the reigning scientific scheme.

Second, my explanation has fallen into a vicious circle. I have made the prehensive unity of region A consist of the prehensive unification of the modal presences of other regions in A. This difficulty arises because space-time cannot really be considered an entity that exists on its own. It is an abstraction, and explaining it requires reference to what it has been abstracted from. Space-time specifies certain general characteristics of events and how they are ordered in relation to one another. This return to concrete fact brings me back to the eighteenth century, and indeed to Francis Bacon in the seventeenth century. We must consider how criticism of the prevailing scientific scheme developed during those periods.

No epoch is homogeneous; whatever you may have assigned as the dominant note of a considerable period, it will always be possible to produce men, and great men, belonging to the same time, who exhibit themselves as antagonistic to the tone of their age. This is certainly the case with the eighteenth century. For example, the names of John Wesley and of Rousseau must have occurred to you while I was drawing the character of that time. But I do not want to speak of them, or of others. The man, whose ideas I must consider at some length, is Bishop Berkeley. Quite at the commencement of the epoch, he made all the right criticisms, at least in principle. It would be untrue to say that he produced no effect. He was a famous man. The wife of George II was one of the few queens who, in any country, have been clever enough, and wise enough, to patronise learning judiciously; accordingly, Berkeley was made a bishop, in days when bishops in Great Britain were relatively far greater men than they are now. Also, what was more important than his bishopric, Hume studied him, and developed one side of his philosophy in a way which might have disturbed the ghost of the great ecclesiastic. Then Kant studied Hume. So, to say that Berkeley was uninfluential during the century, would certainly be absurd. But all the same, he failed to affect the main stream of scientific thought. It flowed on as if he had never written. Its general success made it impervious to criticism, then and since. The world of science has always remained perfectly satisfied with its peculiar abstractions. They work, and that is sufficient for it.

No age is uniform. Whatever you take to be the dominant spirit of a long period, you can always find people who oppose it. Among them will be great people. This is certainly true of the eighteenth century. For example, John Wesley and Rousseau must have come to mind while I was describing that age. But I do not want to speak about them or anyone else. The man whose ideas I must consider at some length is Bishop Berkeley. At the very beginning of the period, Berkeley made all the right criticisms, at least in principle. It would be untrue to say that he had no effect. He was a famous man. The wife of George II was one of the few queens in any country clever and wise enough to support learning with good judgment. As a result, Berkeley was made a bishop. In those days, bishops in Great Britain were relatively far more important than they are now. More important than his bishopric, however, was that Hume studied him. Hume developed one side of Berkeley's philosophy in a way that might have disturbed the great churchman's ghost. Then Kant studied Hume. So it would certainly be absurd to say that Berkeley had no influence during the century. But even so, Berkeley failed to affect the main stream of scientific thought. It flowed on as if he had never written. Its general success made scientific thought resistant to criticism, both then and since. The world of science has always remained perfectly satisfied with its peculiar abstractions. They work, and that is enough for it.

The point before us is that this scientific field of thought is now, in the twentieth century, too narrow for the concrete facts which are before it for analysis. This is true even in physics, and is more especially urgent in the biological sciences. Thus, in order to understand the difficulties of modern scientific thought and also its reactions on the modern world, we should have in our minds some conception of a wider field of abstraction, a more concrete analysis, which shall stand nearer to the complete concreteness of our intuitive experience. Such an analysis should find in itself a niche for the concepts of matter and spirit, as abstractions in terms of which much of our physical experience can be interpreted. It is in the search for this wider basis for scientific thought that Berkeley is so important. He launched his criticism shortly after the schools of Newton and Locke had completed their work, and laid his finger exactly on the weak spots which they had left. I do not propose to consider either the subjective idealism which has been derived from him, or the schools of development which trace their descent from Hume and Kant respectively. My point will be that—whatever the final metaphysics you may adopt—there is another line of development embedded in Berkeley, pointing to the analysis which we are in search of. Berkeley overlooked it, partly by reason of the over-intellectualism of philosophers, and partly by his haste to have recourse to an idealism with its objectivity grounded in the mind of God. You will remember that I have already stated that the key of the problem lies in the notion of simple location. Berkeley, in effect, criticises this notion. He also raises the question, What do we mean by things being realised in the world of nature?

The point is that, in the twentieth century, this scientific framework is too narrow for the concrete facts it must analyze. This is true even in physics, and the problem is especially urgent in the biological sciences. We need to understand the difficulties of modern scientific thought and its effects on the modern world. To do so, we should have some idea of a broader framework of abstraction and a more concrete analysis. Such an analysis should come closer to the full concreteness of our intuitive experience. It should have room for the concepts of matter and spirit as abstractions that can explain much of our physical experience. Berkeley is important to the search for this broader basis for scientific thought. He began his criticism shortly after the schools of Newton and Locke had completed their work. He identified precisely the weak points they had left. I do not intend to consider either the subjective idealism derived from Berkeley or the schools of thought descended from Hume and Kant, respectively. My point is that Berkeley's work contains another line of development, whatever final metaphysics you may adopt. This line points toward the analysis we are seeking. Berkeley overlooked it, partly because philosophers placed too much emphasis on the intellect. He also overlooked it because he was quick to turn to an idealism whose objectivity was grounded in the mind of God. As you will remember, I have already said that the key to the problem lies in the notion of simple location. Berkeley, in effect, criticizes this notion. He also raises the question: What do we mean when we say that things are realized in the world of nature?

In Sections 23 and 24 of his Principles of Human Knowledge, Berkeley gives his answer to this latter question. I will quote some detached sentences from those Sections:

In Sections 23 and 24 of his Principles of Human Knowledge, Berkeley answers this latter question. I will quote some separate sentences from those sections:

“23. But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park, or books existing in a closet, and nobody by to perceive them. I answer, you may so, there is no difficulty in it; but what is all this, I beseech you, more than framing in your mind certain ideas which you call books and trees, and at the same time omitting to frame the idea of any one that may perceive them?...”

“23. But you say, surely nothing is easier than imagining trees in a park, or books in a closet, with nobody there to see them. I answer, yes, you can do that. There is no difficulty in it. But what, I ask you, is this? You are forming ideas in your mind that you call books and trees. At the same time, you are choosing not to form an idea of anyone who might perceive them....”

“When we do our utmost to conceive the existence of external bodies, we are all the while only contemplating our own ideas. But the mind taking no notice of itself, is deluded to think it can and does conceive bodies existing unthought of or without the mind, though at the same time they are apprehended by or exist in itself....”

“When we try our hardest to imagine external bodies existing, we are still only considering our own ideas. But the mind, not noticing itself, is deceived into thinking it can and does imagine bodies existing without being thought of or outside the mind. This happens even though the mind is thinking of those bodies, and they exist within it....”

“24. It is very obvious, upon the least inquiry into our thoughts, to know whether it be possible for us to understand what is meant by the absolute existence of sensible objects in themselves, or without the mind. To me it is evident those words mark out either a direct contradiction, or else nothing at all....”

“24. A brief examination of our thoughts makes it obvious whether we can understand what is meant by the absolute existence of objects we can sense, in themselves or outside the mind. To me, those words clearly express either a direct contradiction or nothing at all....”

Again there is a very remarkable passage in Section 10, of the fourth Dialogue of Berkeley’s Alciphron. I have already quoted it, at greater length, in my Principles of Natural Knowledge:

Again, there is a very remarkable passage in Section 10 of the fourth Dialogue of Berkeley’s Alciphron. I have already quoted it more fully in my Principles of Natural Knowledge:

“Euphranor. Tell me, Alciphron, can you discern the doors, window and battlements of that same castle?

“Euphranor. Tell me, Alciphron, can you see the doors, window, and battlements of that castle?

Alciphron. I cannot. At this distance it seems only a small round tower.

Alciphron. I can't. From this distance, it looks like a small, round tower.

Euph. But I, who have been at it, know that it is no small round tower, but a large square building with battlements and turrets, which it seems you do not see.

Euph. But I have been there, and I know it is not a small round tower. It is a large square building with battlements and turrets, which you seem not to see.

Alc. What will you infer from thence?

Alc. What will you conclude from that?

Euph. I would infer that the very object which you strictly and properly perceive by sight is not that thing which is several miles distant.

Euph. I would conclude that what you actually see is not the thing several miles away.

Alc. Why so?

Alc. Why?

Euph. Because a little round object is one thing, and a great square object is another. Is it not so?...”

Euph. Because a small round object is one thing, and a large square object is another. Isn't that so?...”

Some analogous examples concerning a planet and a cloud are then cited in the dialogue, and this passage finally concludes with:

The dialogue then gives some similar examples involving a planet and a cloud. The passage ends with:

“Euphranor. Is it not plain, therefore, that neither the castle, the planet, nor the cloud, which you see here, are those real ones which you suppose exist at a distance?”

“Euphranor. So isn't it clear that the castle, the planet, and the cloud you see here are not the real ones you believe exist at a distance?”

It is made explicit in the first passage, already quoted, that Berkeley himself adopts an extreme idealistic interpretation. For him mind is the only absolute reality, and the unity of nature is the unity of ideas in the mind of God. Personally, I think that Berkeley’s solution of the metaphysical problem raises difficulties not less than those which he points out as arising from a realistic interpretation of the scientific scheme. There is, however, another possible line of thought, which enables us to adopt anyhow an attitude of provisional realism, and to widen the scientific scheme in a way which is useful for science itself.

The first passage quoted earlier makes clear that Berkeley himself adopts an extreme idealist interpretation. For him, mind is the only absolute reality, and nature is unified because its ideas exist in the mind of God. Personally, I think Berkeley’s solution to the metaphysical problem raises difficulties at least as great as those he identifies in a realist interpretation of the scientific scheme. However, another line of thought allows us to adopt a provisional realism and to broaden the scientific scheme in a way that is useful for science itself.

I recur to the passage from Francis Bacon’s Natural History, already quoted in the previous lecture:

I return to the passage from Francis Bacon’s Natural History, which I quoted in the previous lecture:

“It is certain that all bodies whatsoever, though they have no sense, yet they have perception: ... and whether the body be alterant or altered, evermore a perception precedeth operation; for else all bodies would be alike one to another....”

“It is certain that all bodies, though they have no senses, have perception: ... Whether a body changes another or is changed, perception always comes before action. Otherwise, all bodies would be alike....”

Also in the previous lecture I construed perception (as used by Bacon) as meaning taking account of the essential character of the thing perceived, and I construed sense as meaning cognition. We certainly do take account of things of which at the time we have no explicit cognition. We can even have a cognitive memory of the taking account, without having had a contemporaneous cognition. Also, as Bacon points out by his statement, “... for else all bodies would be alike one to another,” it is evidently some element of the essential character which we take account of, namely something on which diversity is founded and not mere bare logical diversity.

Also, in the previous lecture, I interpreted perception as Bacon used it to mean taking account of the essential character of the thing perceived. I interpreted sense to mean cognition. We certainly do take account of things without being explicitly aware of them at the time. We can even remember having taken account of something without having been aware of it at the time. Also, Bacon points out that “... for else all bodies would be alike one to another.” Clearly, then, we take account of some element of a thing’s essential character. This element is something on which diversity is founded, not mere abstract logical difference.

The word ‘perceive’ is, in our common usage, shot through and through with the notion of cognitive apprehension. So is the word ‘apprehension’, even with the adjective cognitive omitted. I will use the word ‘prehension’ for uncognitive apprehension: by this I mean apprehension which may or or may not be cognitive. Now take Euphranor’s last remark:

In ordinary usage, the word ‘perceive’ is thoroughly bound up with the idea of cognitive apprehension. So is the word ‘apprehension’, even without the adjective cognitive. I will use the word ‘prehension’ for uncognitive apprehension. By this I mean apprehension that may or may not be cognitive. Now consider Euphranor’s last remark:

“Is it not plain, therefore, that neither the castle, the planet, nor the cloud, which you see here, are those real ones which you suppose exist at distance?” Accordingly, there is a prehension, here in this place, of things which have a reference to other places.

“Isn't it clear, then, that the castle, planet, and cloud which you see here are not the real ones you suppose exist at a distance?” So, there is a prehension here, in this place, of things that refer to other places.

Now go back to Berkeley’s sentences, quoted from his Principles of Human Knowledge. He contends that what constitutes the realisation of natural entities is the being perceived within the unity of mind.

Now return to Berkeley’s sentences quoted from his Principles of Human Knowledge. He argues that natural entities become real by being perceived within the unity of mind.

We can substitute the concept, that the realisation is a gathering of things into the unity of a prehension; and that what is thereby realised is the prehension, and not the things. This unity of a prehension defines itself as a here and a now, and the things so gathered into the grasped unity have essential reference to other places and other times. For Berkeley’s mind, I substitute a process of prehensive unification. In order to make intelligible this concept of the progressive realisation of natural occurrences, considerable expansion is required, and confrontation with its actual implications in terms of concrete experience. This will be the task of the subsequent lectures. In the first place, note that the idea of simple location has gone. The things which are grasped into a realised unity, here and now, are not the castle, the cloud, and the planet simply in themselves; but they are the castle, the cloud, and the planet from the standpoint, in space and time, of the prehensive unification. In other words, it is the perspective of the castle over there from the standpoint of the unification here. It is, therefore, aspects of the castle, the cloud, and the planet which are grasped into unity here. You will remember that the idea of perspectives is quite familiar in philosophy. It was introduced by Leibniz, in the notion of his monads mirroring perspectives of the universe. I am using the same notion, only I am toning down his monads into the unified events in space and time. In some ways, there is a greater analogy with Spinoza’s modes; that is why I use the terms ‘mode’ and ‘modal.’ In the analogy with Spinoza, his one substance is for me the one underlying activity of realisation individualising itself in an interlocked plurality of modes. Thus, concrete fact is process. Its primary analysis is into underlying activity of prehension, and into realised prehensive events. Each event is an individual matter of fact issuing from an individualisation of the substrate activity. But individualisation does not mean substantial independence.

We can instead think of realisation as the gathering of things into the unity of a prehension. What is realised is the prehension, not the things. This unity of prehension defines itself as a here and a now. The things gathered into this unity have an essential relation to other places and other times. In place of Berkeley’s mind, I propose a process of prehensive unification. To make this idea of the progressive realisation of natural occurrences intelligible, I must explain it further. I must also examine its actual implications in terms of concrete experience. That will be the task of the lectures that follow. First, note that the idea of simple location has disappeared. The things grasped into a realised unity, here and now, are not simply the castle, the cloud, and the planet in themselves. Rather, they are the castle, the cloud, and the planet as viewed from the standpoint of the prehensive unification in space and time. In other words, it is the perspective of the castle over there, viewed from the standpoint of the unification here. So it is aspects of the castle, the cloud, and the planet that are grasped into unity here. You will remember that the idea of perspectives is quite familiar in philosophy. Leibniz introduced it in his idea of monads mirroring perspectives of the universe. I am using the same idea, but I am recasting his monads as unified events in space and time. In some ways, there is a closer analogy with Spinoza’s modes. That is why I use the terms ‘mode’ and ‘modal.’ In the analogy with Spinoza, his one substance corresponds to what I call the one underlying activity of realisation. This activity individualises itself in an interlocked plurality of modes. Thus, concrete fact is process. Its primary analysis reveals an underlying activity of prehension and realised prehensive events. Each event is an individual matter of fact arising from an individualisation of the underlying activity. But individualisation does not mean substantial independence.

An entity of which we become aware in sense perception is the terminus of our act of perception. I will call such an entity, a ‘sense-object’. For example, green of a definite shade is a sense-object; so is a sound of definite quality and pitch; and so is a definite scent; and a definite quality of touch. The way in which such an entity is related to space during a definite lapse of time is complex. I will say that a sense-object has ‘ingression’ into space-time. The cognitive perception of a sense-object is the awareness of the prehensive unification (into a standpoint A) of various modes of various sense-objects, including the sense-object in question. The standpoint A is, of course, a region of space-time; that is to say, it is a volume of space through a duration of time. But as one entity, this standpoint is a unit of realised experience. A mode of a sense-object at A (as abstracted from the sense-object whose relationship to A the mode is conditioning) is the aspect from A of some other region B. Thus the sense-object is present in A with the mode of location in B. Thus if green be the sense-object in question, green is not simply at A where it is being perceived, nor is it simply at B where it is perceived as located; but it is present at A with the mode of location in B. There is no particular mystery about this. You have only got to look into a mirror and to see the image in it of some green leaves behind your back. For you at A there will be green; but not green simply at A where you are. The green at A will be green with the mode of having location at the image of the leaf behind the mirror. Then turn round and look at the leaf. You are now perceiving the green in the same way as you did before, except that now the green has the mode of being located in the actual leaf. I am merely describing what we do perceive: we are aware of green as being one element in a prehensive unification of sense-objects; each sense-object, and among them green, having its particular mode, which is expressible as location elsewhere. There are various types of modal location. For example, sound is voluminous: it fills a hall, and so sometimes does diffused colour. But the modal location of a colour may be that of being the remote boundary of a volume, as for example the colours on the walls of a room. Thus primarily space-time is the locus of the modal ingression of sense-objects. This is the reason why space and time (if for simplicity we disjoin them) are given in their entireties. For each volume of space, or each lapse of time, includes in its essence aspects of all volumes of space, or of all lapses of time. The difficulties of philosophy in respect to space and time are founded on the error of considering them as primarily the loci of simple locations. Perception is simply the cognition of prehensive unification; or more shortly, perception is cognition of prehension. The actual world is a manifold of prehensions; and a ‘prehension’ is a ‘prehensive occasion’; and a prehensive occasion is the most concrete finite entity, conceived as what it is in itself and for itself, and not as from its aspect in the essence of another such occasion. Prehensive unification might be said to have simple location in its volume A. But this would be a mere tautology. For space and time are simply abstractions from the totality of prehensive unifications as mutually patterned in each other. Thus a prehension has simple location at the volume A in the same way as that in which a man’s face fits on to the smile which spreads over it. There is, so far as we have gone, more sense in saying that an act of perception has simple location; for it may be conceived as being simply at the cognised prehension.

An entity we become aware of through sense perception is the endpoint of our act of perception. I will call such an entity a ‘sense-object’. For example, green of a definite shade is a sense-object. So are a sound of definite quality and pitch, a definite scent, and a definite quality of touch. A sense-object’s relationship to space over a definite period of time is complex. I will say that a sense-object has ‘ingression’ into space-time. To perceive a sense-object is to be aware of a prehensive unification into a standpoint A. What is unified are various modes of various sense-objects, including the sense-object being perceived. Standpoint A is, of course, a region of space-time. That is, it is a volume of space over a period of time. But as one entity, this standpoint is a unit of realised experience. A mode of a sense-object at A is the aspect of some other region B as seen from A. This mode is considered apart from the sense-object whose relationship to A it conditions. Thus the sense-object is present in A with the mode of location in B. So if green is the sense-object in question, it is not simply at A, where it is perceived. Nor is it simply at B, where it is perceived as being located. Rather, green is present at A with the mode of location in B. There is no particular mystery about this. You only have to look into a mirror and see the image of some green leaves behind your back. For you at A, there will be green, but not green simply at A, where you are. The green at A will have the mode of being located at the image of the leaf behind the mirror. Then turn around and look at the leaf. You are now perceiving the green in the same way as before. The difference is that the green now has the mode of being located in the actual leaf. I am merely describing what we do perceive. We are aware of green as one element in a prehensive unification of sense-objects. Each sense-object, including green, has its own mode, which can be expressed as location elsewhere. There are various types of modal location. For example, sound has volume. It fills a hall, and diffused colour sometimes does too. But the modal location of a colour may be the remote boundary of a volume. The colours on the walls of a room are an example. Thus space-time is primarily the locus of the modal ingression of sense-objects. This is why space and time, if we separate them for simplicity, are given in their entireties. For each volume of space includes in its essence aspects of all volumes of space. Likewise, each lapse of time includes in its essence aspects of all lapses of time. Philosophy’s difficulties with space and time arise from the error of treating them primarily as loci of simple locations. Perception is simply the cognition of prehensive unification. More briefly, perception is cognition of prehension. The actual world is a manifold of prehensions. A ‘prehension’ is a ‘prehensive occasion’. A prehensive occasion is the most concrete finite entity, considered as what it is in itself and for itself. It is not considered as it appears in the essence of another such occasion. Prehensive unification might be said to have simple location in its volume A. But this would be a mere tautology. For space and time are simply abstractions from the totality of prehensive unifications, as they are mutually patterned in each other. Thus a prehension has simple location at the volume A. It has that location in the same way that a man’s face fits the smile spreading over it. So far, it makes more sense to say that an act of perception has simple location. For an act of perception may be thought of as being simply at the prehension that is cognised.

There are more entities involved in nature than the mere sense-objects, so far considered. But, allowing for the necessity of revision consequent on a more complete point of view, we can frame our answer to Berkeley’s question as to the character of the reality to be assigned to nature. He states it to be the reality of ideas in mind. A complete metaphysic which has attained to some notion of mind, and to some notion of ideas, may perhaps ultimately adopt that view. It is unnecessary for the purpose of these lectures to ask such a fundamental question. We can be content with a provisional realism in which nature is conceived as a complex of prehensive unifications. Space and time exhibit the general scheme of interlocked relations of these prehensions. You cannot tear any one of them out of its context. Yet each one of them within its context has all the reality that attaches to the whole complex. Conversely, the totality has the same reality as each prehension; for each prehension unifies the modalities to be ascribed, from its standpoint, to every part of the whole. A prehension is a process of unifying. Accordingly, nature is a process of expansive development, necessarily transitional from prehension to prehension. What is achieved is thereby passed beyond, but it is also retained as having aspects of itself present to prehensions which lie beyond it.

Nature involves more entities than the sense objects considered so far. Still, we can offer an answer to Berkeley’s question about the kind of reality we should assign to nature. We must allow for revising that answer in light of a more complete point of view. Berkeley says that nature has the reality of ideas in the mind. A complete metaphysics, with some conception of mind and some conception of ideas, may perhaps ultimately adopt that view. But these lectures do not need to address such a fundamental question. We can be content with a provisional realism that conceives nature as a complex of prehensive unifications. Space and time show the general pattern of interlocking relations among these prehensions. You cannot separate any one prehension from its context. Yet each prehension, within its context, has all the reality that belongs to the whole complex. Conversely, the whole has the same reality as each prehension. Each prehension unifies the qualities that, from its standpoint, belong to every part of the whole. A prehension is a process of unifying. Nature, therefore, is a process of expansive development, necessarily moving from one prehension to another. What is achieved is passed beyond. But it is also retained, because aspects of it remain present to the prehensions that come after it.

Thus nature is a structure of evolving processes. The reality is the process. It is nonsense to ask if the colour red is real. The colour red is ingredient in the process of realisation. The realities of nature are the prehensions in nature, that is to say, the events in nature.

So nature is a structure of evolving processes. The process itself is what is real. It makes no sense to ask whether the color red is real. The color red is part of the process of realization. The realities of nature are the prehensions in nature, that is, the events in nature.

Now that we have cleared space and time from the taint of simple location, we may partially abandon the awkward term prehension. This term was introduced to signify the essential unity of an event, namely, the event as one entity, and not as a mere assemblage of parts or of ingredients. It is necessary to understand that space-time is nothing else than a system of pulling together of assemblages into unities. But the word event just means one of these spatio-temporal unities. Accordingly, it may be used instead of the term ‘prehension’ as meaning the thing prehended.

Now that we have freed space and time from the taint of simple location, we may partly set aside the awkward term prehension. The term was introduced to express the essential unity of an event. An event is one entity, not just a collection of parts or ingredients. We must understand that space-time is nothing more than a system that draws collections together into unities. But the word event simply means one of these spatio-temporal unities. So it may be used instead of ‘prehension’ to mean the thing prehended.

An event has contemporaries. This means that an event mirrors within itself the modes of its contemporaries as a display of immediate achievement. An event has a past. This means that an event mirrors within itself the modes of its predecessors, as memories which are fused into its own content. An event has a future. This means that an event mirrors within itself such aspects as the future throws back onto the present, or, in other words, as the present has determined concerning the future. Thus an event has anticipation:

An event has contemporaries. This means that an event reflects within itself the forms of contemporary events as a display of immediate achievement. An event has a past. This means that an event reflects within itself the forms of earlier events as memories fused into its own content. An event has a future. This means that an event reflects within itself the aspects that the future casts back onto the present. In other words, the event reflects what the present has determined about the future. Thus, an event has anticipation:

These conclusions are essential for any form of realism. For there is in the world for our cognisance, memory of the past, immediacy of realisation, and indication of things to come.

These conclusions are essential to any form of realism. For the world we know includes memory of the past, immediate experience, and signs of things to come.

In this sketch of an analysis more concrete than that of the scientific scheme of thought, I have started from our own psychological field, as it stands for our cognition. I take it for what it claims to be: the self-knowledge of our bodily event. I mean the total event, and not the inspection of the details of the body. This self-knowledge discloses a prehensive unification of modal presences of entities beyond itself. I generalise by the use of the principle that this total bodily event is on the same level as all other events, except for an unusual complexity and stability of inherent pattern. The strength of the theory of materialistic mechanism has been the demand, that no arbitrary breaks be introduced into nature, to eke out the collapse of an explanation. I accept this principle. But if you start from the immediate facts of our psychological experience, as surely an empiricist should begin, you are at once led to the organic conception of nature of which the description has been commenced in this lecture.

In this sketch, I offer an analysis more concrete than that of the scientific scheme of thought. I begin with our own psychological field, as we know it. I take it to be what it claims to be: the self-knowledge of our bodily event. I mean the event as a whole, not an inspection of the body’s details. This self-knowledge reveals a prehensive unification of the various ways in which entities beyond it are present. I generalize from the principle that this total bodily event is on the same level as all other events. It differs only in the unusual complexity and stability of its inherent pattern. The strength of materialistic mechanism has been its demand that no arbitrary breaks be introduced into nature to make up for a failed explanation. I accept this principle. But an empiricist should surely begin with the immediate facts of our psychological experience. If you begin there, you are immediately led to the organic conception of nature that I have begun to describe in this lecture.

It is the defect of the eighteenth century scientific scheme that it provides none of the elements which compose the immediate psychological experiences of mankind. Nor does it provide any elementary trace of the organic unity of a whole, from which the organic unities of electrons, protons, molecules, and living bodies can emerge. According to that scheme, there is no reason in the nature of things why portions of material should have any physical relations to each other. Let us grant that we cannot hope to be able to discern the laws of nature to be necessary. But we can hope to see that it is necessary that there should be an order of nature. The concept of the order of nature is bound up with the concept of nature as the locus of organisms in process of development.

The eighteenth-century scientific framework has a flaw. It provides none of the elements that make up our immediate psychological experiences. Nor does it provide even a basic trace of the organic unity of a whole. From such unity, the organic unities of electrons, protons, molecules, and living bodies could emerge. According to this framework, there is no reason in the nature of things for portions of matter to have any physical relations to each other. Let us grant that we cannot hope to see the laws of nature as necessary. But we can hope to see that an order of nature is necessary. The idea of an order of nature is bound up with the idea of nature as the place where organisms develop.