Academic or Skeptical Philosophy

116. There is not a greater number of philosophical reasonings, displayed upon any subject, than those, which prove the existence of a Deity, and refute the fallacies of Atheists; and yet the most religious philosophers still dispute whether any man can be so blinded as to be a speculative atheist. How shall we reconcile these contradictions? The knights-errant, who wandered about to clear the world of dragons and giants, never entertained the least doubt with regard to the existence of these monsters.

116. No subject has inspired more philosophical arguments than those proving the existence of God and exposing the false reasoning of Atheists. Yet even the most religious philosophers still dispute whether anyone can be so blind as to be an atheist in theory. How can we reconcile these contradictions? The knights-errant who wandered the world to rid it of dragons and giants never doubted that these monsters existed.

The Sceptic is another enemy of religion, who naturally provokes the indignation of all divines and graver philosophers; though it is certain, that no man ever met with any such absurd creature, or conversed with a man, who had no opinion or principle concerning any subject, either of action or speculation. This begets a very natural question; What is meant by a sceptic? And how far it is possible to push these philosophical principles of doubt and uncertainty?

The skeptic is another enemy of religion who naturally provokes the indignation of all theologians and more serious philosophers. Yet no one has ever met such an absurd creature. No one has ever spoken with a person who had no opinion or principle on any subject, whether practical or theoretical. This raises a natural question: What is a skeptic? And how far can these philosophical principles of doubt and uncertainty be taken?

There is a species of scepticism, antecedent to all study and philosophy, which is much inculcated by Des Cartes and others, as a sovereign preservative against error and precipitate judgement. It recommends an universal doubt, not only of all our former opinions and principles, but also of our very faculties; of whose veracity, say they, we must assure ourselves, by a chain of reasoning, deduced from some original principle, which cannot possibly be fallacious or deceitful. But neither is there any such original principle, which has a prerogative above others, that are self-evident and convincing: or if there were, could we advance a step beyond it, but by the use of those very faculties, of which we are supposed to be already diffident. The Cartesian doubt, therefore, were it ever possible to be attained by any human creature (as it plainly is not) would be entirely incurable; and no reasoning could ever bring us to a state of assurance and conviction upon any subject.

There is a kind of scepticism that comes before all study and philosophy. Des Cartes and others strongly recommend it as a sure protection against error and hasty judgment. This scepticism calls for universal doubt, not only of all our former opinions and principles, but also of our own faculties. Its advocates say that we must establish the reliability of those faculties through a chain of reasoning. This reasoning must begin with an original principle that cannot possibly be false or misleading. But no such original principle has a special claim to authority over other principles that are self-evident and convincing. Even if there were such a principle, could we move a single step beyond it without using those very faculties we are supposed to distrust? Cartesian doubt, therefore, would be impossible to overcome, even if any human being could ever achieve it (as plainly no one can). No reasoning could ever bring us to assurance and conviction about any subject.

It must, however, be confessed, that this species of scepticism, when more moderate, may be understood in a very reasonable sense, and is a necessary preparative to the study of philosophy, by preserving a proper impartiality in our judgements, and weaning our mind from all those prejudices, which we may have imbibed from education or rash opinion. To begin with clear and self-evident principles, to advance by timorous and sure steps, to review frequently our conclusions, and examine accurately all their consequences; though by these means we shall make both a slow and a short progress in our systems; are the only methods, by which we can ever hope to reach truth, and attain a proper stability and certainty in our determinations.

We must admit, however, that a more moderate form of this skepticism can be understood in a very reasonable way. It is a necessary preparation for studying philosophy. It helps us judge with proper impartiality and frees our minds from all the prejudices absorbed through education or rash opinions. We should begin with clear, self-evident principles and advance in cautious, sure steps. We should frequently review our conclusions and carefully examine all their consequences. These methods will bring us only slow and limited progress in building our systems of thought. Yet they are the only methods by which we can hope to reach the truth and achieve proper stability and certainty in our judgments.

117. There is another species of scepticism, consequent to science and enquiry, when men are supposed to have discovered, either the absolute fallaciousness of their mental faculties, or their unfitness to reach any fixed determination in all those curious subjects of speculation, about which they are commonly employed. Even our very senses are brought into dispute, by a certain species of philosophers; and the maxims of common life are subjected to the same doubt as the most profound principles or conclusions of metaphysics and theology. As these paradoxical tenets (if they may be called tenets) are to be met with in some philosophers, and the refutation of them in several, they naturally excite our curiosity, and make us enquire into the arguments, on which they may be founded.

117. There is another kind of scepticism that comes after science and inquiry. It arises when people believe they have discovered that their mental faculties are completely unreliable. Or they believe these faculties cannot reach any definite conclusion on any of the complex questions they usually investigate. Some philosophers even question our senses. They subject the principles of everyday life to the same doubt as the deepest principles or conclusions of metaphysics and theology. Some philosophers hold these paradoxical views, if they can be called views, and several others have tried to refute them. These views naturally arouse our curiosity and lead us to ask what arguments might support them.

I need not insist upon the more trite topics, employed by the sceptics in all ages, against the evidence of sense; such as those which are derived from the imperfection and fallaciousness of our organs, on numberless occasions; the crooked appearance of an oar in water; the various aspects of objects, according to their different distances; the double images which arise from the pressing one eye; with many other appearances of a like nature. These sceptical topics, indeed, are only sufficient to prove, that the senses alone are not implicitly to be depended on; but that we must correct their evidence by reason, and by considerations, derived from the nature of the medium, the distance of the object, and the disposition of the organ, in order to render them, within their sphere, the proper criteria of truth and falsehood. There are other more profound arguments against the senses, which admit not of so easy a solution.

I need not dwell on the familiar arguments skeptics in every age have used against the evidence of the senses. These arguments point to the countless occasions when our sense organs are imperfect and misleading. An oar looks crooked in water. Objects look different at different distances. Pressing one eye produces double images. There are many other appearances of the same kind. These skeptical arguments, however, prove only that the senses alone cannot be trusted without question. We must correct their evidence through reason and by considering the nature of the medium, the object's distance, and the condition of the sense organ. Only then can the senses serve, within their proper sphere, as criteria of truth and falsehood. There are other, more profound arguments against the senses that cannot be resolved so easily.

118. It seems evident, that men are carried, by a natural instinct or prepossession, to repose faith in their senses; and that, without any reasoning, or even almost before the use of reason, we always suppose an external universe, which depends not on our perception, but would exist, though we and every sensible creature were absent or annihilated. Even the animal creation are governed by a like opinion, and preserve this belief of external objects, in all their thoughts, designs, and actions.

118. It seems clear that a natural instinct or bias leads people to trust their senses. Without reasoning, and even almost before we can reason, we always assume that an external universe exists independently of our perception. We assume it would exist even if we and every creature capable of sensation were absent or destroyed. Animals are guided by a similar belief. They retain their belief in external objects in all their thoughts, plans, and actions.

It seems also evident, that, when men follow this blind and powerful instinct of nature, they always suppose the very images, presented by the senses, to be the external objects, and never entertain any suspicion, that the one are nothing but representations of the other. This very table, which we see white, and which we feel hard, is believed to exist, independent of our perception, and to be something external to our mind, which perceives it. Our presence bestows not being on it: our absence does not annihilate it. It preserves its existence uniform and entire, independent of the situation of intelligent beings, who perceive or contemplate it.

It also seems clear that people follow a blind and powerful natural instinct. When they do, they always assume that the images presented by their senses are the external objects themselves. They never suspect that these images are merely representations of those objects. We believe that this table, which we see as white and feel as hard, exists independently of our perception. We believe it exists outside the mind that perceives it. Our presence does not bring the table into being, and our absence does not destroy it. Its existence remains unchanged and complete, regardless of the situation of the intelligent beings who perceive or contemplate it.

But this universal and primary opinion of all men is soon destroyed by the slightest philosophy, which teaches us, that nothing can ever be present to the mind but an image or perception, and that the senses are only the inlets, through which these images are conveyed, without being able to produce any immediate intercourse between the mind and the object. The table, which we see, seems to diminish, as we remove farther from it: but the real table, which exists independent of us, suffers no alteration: it was, therefore, nothing but its image, which was present to the mind. These are the obvious dictates of reason; and no man, who reflects, ever doubted, that the existences, which we consider, when we say, this house and that tree, are nothing but perceptions in the mind, and fleeting copies or representations of other existences, which remain uniform and independent.

But even the slightest philosophy soon destroys this universal and basic belief shared by all people. Philosophy teaches us that only an image or perception can ever be present to the mind. The senses are merely channels through which these images reach us. They cannot put the mind in direct contact with an object. A table appears to grow smaller as we move farther away from it. But the real table, which exists independently of us, does not change. So only its image was present to the mind. These are the obvious conclusions of reason. Anyone who reflects knows that what we are thinking of when we say this house and that tree are only perceptions in the mind. They are fleeting copies or representations of other things, which remain unchanged and independent.

119. So far, then, are we necessitated by reasoning to contradict or depart from the primary instincts of nature, and to embrace a new system with regard to the evidence of our senses. But here philosophy finds herself extremely embarrassed, when she would justify this new system, and obviate the cavils and objections of the sceptics. She can no longer plead the infallible and irresistible instinct of nature: for that led us to a quite different system, which is acknowledged fallible and even erroneous. And to justify this pretended philosophical system, by a chain of clear and convincing argument, or even any appearance of argument, exceeds the power of all human capacity.

119. Reason therefore forces us to depart from our basic natural instincts and even contradict them. It forces us to adopt a new system for understanding the evidence of our senses. But philosophy faces a serious difficulty when it tries to justify this new system and answer the skeptics’ criticisms and objections. It can no longer appeal to the supposedly infallible and irresistible instinct of nature. For that instinct led us to a quite different system, which is acknowledged to be fallible and even mistaken. And no human being can justify this so-called philosophical system with a chain of clear and convincing arguments, or even with anything resembling an argument.

By what argument can it be proved, that the perceptions of the mind must be caused by external objects, entirely different from them, though resembling them (if that be possible) and could not arise either from the energy of the mind itself, or from the suggestion of some invisible and unknown spirit, or from some other cause still more unknown to us? It is acknowledged, that, in fact, many of these perceptions arise not from anything external, as in dreams, madness, and other diseases. And nothing can be more inexplicable than the manner, in which body should so operate upon mind as ever to convey an image of itself to a substance, supposed of so different, and even contrary a nature.

What argument can prove that the mind’s perceptions must be caused by external objects? These objects would be entirely different from the perceptions, though they would resemble them, if that is possible. Could the perceptions not arise from the activity of the mind itself? Could they not come from the influence of an invisible and unknown spirit, or from some other cause even less known to us? We acknowledge that many perceptions do not, in fact, arise from anything external, as in dreams, madness, and other illnesses. And nothing could be harder to explain than how a body could act on the mind and convey an image of itself to it. For the mind is supposed to be a substance of a very different, even opposite, nature.

It is a question of fact, whether the perceptions of the senses be produced by external objects, resembling them: how shall this question be determined? By experience surely; as all other questions of a like nature. But here experience is, and must be entirely silent. The mind has never anything present to it but the perceptions, and cannot possibly reach any experience of their connexion with objects. The supposition of such a connexion is, therefore, without any foundation in reasoning.

It is a question of fact whether external objects cause our sensory perceptions and resemble them. How can we settle this question? Surely, by experience, as with all other questions of this kind. But here experience is, and must be, entirely silent. The mind has access only to its perceptions. It cannot possibly experience any connection between those perceptions and objects. Therefore, the assumption that such a connection exists has no basis in reason.

120. To have recourse to the veracity of the supreme Being, in order to prove the veracity of our senses, is surely making a very unexpected circuit. If his veracity were at all concerned in this matter, our senses would be entirely infallible; because it is not possible that he can ever deceive. Not to mention, that, if the external world be once called in question, we shall be at a loss to find arguments, by which we may prove the existence of that Being or any of his attributes.

120. To appeal to the supreme Being’s truthfulness to prove that our senses are reliable is surely a very unexpected detour. If his truthfulness were involved in this matter, our senses would be completely infallible. This is because he cannot deceive. Moreover, once the external world is called into question, we will struggle to find arguments proving his existence or any of his attributes.

121. This is a topic, therefore, in which the profounder and more philosophical sceptics will always triumph, when they endeavour to introduce an universal doubt into all subjects of human knowledge and enquiry. Do you follow the instincts and propensities of nature, may they say, in assenting to the veracity of sense? But these lead you to believe that the very perception or sensible image is the external object. Do you disclaim this principle, in order to embrace a more rational opinion, that the perceptions are only representations of something external? You here depart from your natural propensities and more obvious sentiments; and yet are not able to satisfy your reason, which can never find any convincing argument from experience to prove, that the perceptions are connected with any external objects.

121. On this topic, therefore, the deeper and more philosophical skeptics will always triumph. They triumph when they try to cast universal doubt on every subject of human knowledge and inquiry. They may ask: Do you follow your natural instincts and tendencies in trusting your senses? But these instincts and tendencies lead you to believe that the perception or sensory image itself is the external object. Do you reject this principle in favor of a more rational view? Do you believe that perceptions are only representations of something external? If so, you depart from your natural tendencies and more obvious feelings. Yet you still cannot satisfy your reason. Reason can never find a convincing argument from experience to prove that perceptions are connected with any external objects.

122. There is another sceptical topic of a like nature, derived from the most profound philosophy; which might merit our attention, were it requisite to dive so deep, in order to discover arguments and reasonings, which can so little serve to any serious purpose. It is universally allowed by modern enquirers, that all the sensible qualities of objects, such as hard, soft, hot, cold, white, black, &c. are merely secondary, and exist not in the objects themselves, but are perceptions of the mind, without any external archetype or model, which they represent. If this be allowed, with regard to secondary qualities, it must also follow, with regard to the supposed primary qualities of extension and solidity; nor can the latter be any more entitled to that denomination than the former. The idea of extension is entirely acquired from the senses of sight and feeling; and if all the qualities, perceived by the senses, be in the mind, not in the object, the same conclusion must reach the idea of extension, which is wholly dependent on the sensible ideas or the ideas of secondary qualities. Nothing can save us from this conclusion, but the asserting, that the ideas of those primary qualities are attained by Abstraction, an opinion, which, if we examine it accurately, we shall find to be unintelligible, and even absurd. An extension, that is neither tangible nor visible, cannot possibly be conceived: and a tangible or visible extension, which is neither hard nor soft, black nor white, is equally beyond the reach of human conception. Let any man try to conceive a triangle in general, which is neither Isosceles nor Scalenum, nor has any particular length or proportion of sides; and he will soon perceive the absurdity of all the scholastic notions with regard to abstraction and general ideas.³¹

122. There is another sceptical argument of a similar kind, drawn from the most profound philosophy. It might deserve our attention if we needed to dig so deep to find arguments that serve so little serious purpose. Modern thinkers universally agree that all the qualities we sense in objects are merely secondary qualities. These include hardness, softness, heat, cold, whiteness, blackness, and so on. These qualities do not exist in the objects themselves. They are perceptions in the mind, with no external original or model that they represent. If we accept this for secondary qualities, the same must follow for the supposed primary qualities of extension and solidity. These qualities have no better claim to be called primary than the others. Our idea of extension comes entirely from sight and touch. So if all the qualities perceived by the senses exist in the mind, not in the object, the same must be true of extension. The idea of extension depends entirely on ideas from the senses, or ideas of secondary qualities. We can escape this conclusion only by claiming that we acquire ideas of primary qualities through Abstraction. But if we examine that view closely, we will find it unintelligible and even absurd. We cannot possibly conceive of extension that can be neither touched nor seen. Nor can we conceive of visible or tangible extension that is neither hard nor soft, black nor white. Let anyone try to conceive of a triangle in general, one that is neither Isosceles nor Scalenum, and whose sides have no particular length or proportion. He will soon see the absurdity of all the scholastic notions about abstraction and general ideas.³¹

123. Thus the first philosophical objection to the evidence of sense or to the opinion of external existence consists in this, that such an opinion, if rested on natural instinct, is contrary to reason, and if referred to reason, is contrary to natural instinct, and at the same time carries no rational evidence with it, to convince an impartial enquirer. The second objection goes farther, and represents this opinion as contrary to reason: at least, if it be a principle of reason, that all sensible qualities are in the mind, not in the object. Bereave matter of all its intelligible qualities, both primary and secondary, you in a manner annihilate it, and leave only a certain unknown, inexplicable something, as the cause of our perceptions; a notion so imperfect, that no sceptic will think it worth while to contend against it.

123. The first philosophical objection to the evidence of the senses, or to belief in external existence, is this. If that belief rests on natural instinct, it conflicts with reason. If it rests on reason, it conflicts with natural instinct. At the same time, it has no rational evidence to convince an impartial inquirer. The second objection goes further. It presents this belief as contrary to reason, at least if reason holds that all sensible qualities are in the mind, not in the object. Remove all the intelligible qualities of matter, both primary and secondary, and you in a way destroy it. All that remains is an unknown, inexplicable something as the cause of our perceptions. This notion is so imperfect that no skeptic will think it worth arguing against.

124. It may seem a very extravagant attempt of the sceptics to destroy reason by argument and ratiocination; yet is this the grand scope of all their enquiries and disputes. They endeavour to find objections, both to our abstract reasonings, and to those which regard matter of fact and existence.

124. The skeptics’ attempt to destroy reason through argument and reasoning may seem extreme. Yet this is the main aim of all their inquiries and disputes. They try to find objections to both abstract reasoning and reasoning about matters of fact and existence.

The chief objection against all abstract reasonings is derived from the ideas of space and time; ideas, which, in common life and to a careless view, are very clear and intelligible, but when they pass through the scrutiny of the profound sciences (and they are the chief object of these sciences) afford principles, which seem full of absurdity and contradiction. No priestly dogmas, invented on purpose to tame and subdue the rebellious reason of mankind, ever shocked common sense more than the doctrine of the infinitive divisibility of extension, with its consequences; as they are pompously displayed by all geometricians and metaphysicians, with a kind of triumph and exultation. A real quantity, infinitely less than any finite quantity, containing quantities infinitely less than itself, and so on in infinitum; this is an edifice so bold and prodigious, that it is too weighty for any pretended demonstration to support, because it shocks the clearest and most natural principles of human reason.³² But what renders the matter more extraordinary, is, that these seemingly absurd opinions are supported by a chain of reasoning, the clearest and most natural; nor is it possible for us to allow the premises without admitting the consequences. Nothing can be more convincing and satisfactory than all the conclusions concerning the properties of circles and triangles; and yet, when these are once received, how can we deny, that the angle of contact between a circle and its tangent is infinitely less than any rectilineal angle, that as you may increase the diameter of the circle in infinitum, this angle of contact becomes still less, even in infinitum, and that the angle of contact between other curves and their tangents may be infinitely less than those between any circle and its tangent, and so on, in infinitum? The demonstration of these principles seems as unexceptionable as that which proves the three angles of a triangle to be equal to two right ones, though the latter opinion be natural and easy, and the former big with contradiction and absurdity. Reason here seems to be thrown into a kind of amazement and suspence, which, without the suggestions of any sceptic, gives her a diffidence of herself, and of the ground on which she treads. She sees a full light, which illuminates certain places; but that light borders upon the most profound darkness. And between these she is so dazzled and confounded, that she scarcely can pronounce with certainty and assurance concerning any one object.

The chief objection to all abstract reasoning comes from the ideas of space and time. In everyday life, and at a casual glance, these ideas seem very clear and understandable. But they are the chief subject of the deeper sciences, and close examination by those sciences yields principles that seem full of absurdity and contradiction. Priests have invented dogmas expressly to tame and subdue humanity’s rebellious reason. Yet none has ever shocked common sense more than the doctrine that extension is infinitely divisible, along with its consequences. All geometers and metaphysicians display this doctrine and its consequences with pomp, as if in triumph and delight. Consider a real quantity, infinitely smaller than any finite quantity, containing quantities infinitely smaller than itself, and so on without end. This is such a bold and enormous structure that it is too heavy for any supposed proof to support. For it offends the clearest and most natural principles of human reason.³² But what makes the matter even more extraordinary is that these seemingly absurd opinions rest on a chain of reasoning that is perfectly clear and natural. We cannot accept the premises without also accepting the consequences. Nothing could be more convincing and satisfying than all the conclusions about the properties of circles and triangles. Yet, once we accept them, how can we deny what follows? The angle of contact between a circle and its tangent is infinitely smaller than any angle formed by straight lines. As we can increase the circle’s diameter without end, this angle of contact becomes smaller, also without end. And the angle of contact between other curves and their tangents may be infinitely smaller than that between any circle and its tangent, and so on, without end. The proof of these principles seems as sound as the proof that a triangle’s three angles equal two right angles. Yet the latter conclusion is natural and easy to accept, while the former is full of contradiction and absurdity. Here reason seems stunned and uncertain. Without any prompting from a skeptic, reason comes to distrust itself and the ground it stands on. It sees a bright light that illuminates certain places, but that light borders on the deepest darkness. Between light and darkness, reason is so dazzled and confused that it can hardly speak with certainty or confidence about any object.

125. The absurdity of these bold determinations of the abstract sciences seems to become, if possible, still more palpable with regard to time than extension. An infinite number of real parts of time, passing in succession, and exhausted one after another, appears so evident a contradiction, that no man, one should think, whose judgement is not corrupted, instead of being improved, by the sciences, would ever be able to admit of it.

125. The absurdity of these bold conclusions of the abstract sciences seems, if possible, even more obvious with time than with space. An infinite number of real parts of time, passing in succession and being used up one after another, seems an obvious contradiction. One would think that no one could accept this, unless the sciences had corrupted their judgment instead of improving it.

Yet still reason must remain restless, and unquiet, even with regard to that scepticism, to which she is driven by these seeming absurdities and contradictions. How any clear, distinct idea can contain circumstances, contradictory to itself, or to any other clear, distinct idea, is absolutely incomprehensible; and is, perhaps, as absurd as any proposition, which can be formed. So that nothing can be more sceptical, or more full of doubt and hesitation, than this scepticism itself, which arises from some of the paradoxical conclusions of geometry or the science of quantity.³³

Yet reason must still remain restless and uneasy, even about the skepticism these apparent absurdities and contradictions force upon it. It is absolutely incomprehensible how a clear, distinct idea can contain features that contradict itself or another clear, distinct idea. Perhaps this is as absurd as any proposition that can be put forward. So nothing can be more skeptical, or more full of doubt and hesitation, than this skepticism itself. It arises from some of the paradoxical conclusions of geometry, or the science of quantity.³³

126. The sceptical objections to moral evidence, or to the reasonings concerning matter of fact, are either popular or philosophical. The popular objections are derived from the natural weakness of human understanding; the contradictory opinions, which have been entertained in different ages and nations; the variations of our judgement in sickness and health, youth and old age, prosperity and adversity; the perpetual contradiction of each particular man's opinions and sentiments; with many other topics of that kind. It is needless to insist farther on this head. These objections are but weak. For as, in common life, we reason every moment concerning fact and existence, and cannot possibly subsist, without continually employing this species of argument, any popular objections, derived from thence, must be insufficient to destroy that evidence. The great subverter of Pyrrhonism or the excessive principles of scepticism is action, and employment, and the occupations of common life. These principles may flourish and triumph in the schools; where it is, indeed, difficult, if not impossible, to refute them. But as soon as they leave the shade, and by the presence of the real objects, which actuate our passions and sentiments, are put in opposition to the more powerful principles of our nature, they vanish like smoke, and leave the most determined sceptic in the same condition as other mortals.

126. Skeptical objections to moral evidence, or reasoning about matters of fact, are either popular or philosophical. Popular objections arise from the natural weakness of human understanding. They also arise from the conflicting opinions held in different ages and nations, and from changes in our judgment during sickness and health, youth and old age, prosperity and adversity. They arise, too, from the constant contradictions in each person’s opinions and feelings, and from many other examples of this kind. There is no need to discuss these objections further. They are weak. In everyday life, we reason constantly about facts and existence. We could not possibly survive without continually using this kind of reasoning. So popular objections based on these weaknesses cannot destroy the force of such evidence. The great force that overthrows Pyrrhonism, or excessive skepticism, is action and the business of everyday life. These principles may flourish and triumph in academic settings, where they are indeed difficult, if not impossible, to refute. But as soon as they leave the shelter of those settings, they face real objects that stir our passions and feelings. When they are set against the stronger principles of our nature, they vanish like smoke. They leave even the most determined skeptic in the same condition as other mortals.

127. The sceptic, therefore, had better keep within his proper sphere, and display those philosophical objections, which arise from more profound researches. Here he seems to have ample matter of triumph; while he justly insists, that all our evidence for any matter of fact, which lies beyond the testimony of sense or memory, is derived entirely from the relation of cause and effect; that we have no other idea of this relation than that of two objects, which have been frequently conjoined together; that we have no argument to convince us, that objects, which have, in our experience, been frequently conjoined, will likewise, in other instances, be conjoined in the same manner; and that nothing leads us to this inference but custom or a certain instinct of our nature; which it is indeed difficult to resist, but which, like other instincts, may be fallacious and deceitful. While the sceptic insists upon these topics, he shows his force, or rather, indeed, his own and our weakness; and seems, for the time at least, to destroy all assurance and conviction. These arguments might be displayed at greater length, if any durable good or benefit to society could ever be expected to result from them.

127. The sceptic should therefore stay within their proper sphere and present the philosophical objections that arise from deeper inquiry. Here the sceptic seems to have plenty of grounds for triumph. The sceptic rightly insists that all our evidence for matters of fact beyond what our senses or memory tell us comes entirely from the relation of cause and effect. We have no other idea of this relation than that of two objects frequently joined together. We have no argument to convince us that objects frequently joined in our experience will be joined in the same way in other cases. Only habit or a certain natural instinct leads us to draw this conclusion. This instinct is indeed difficult to resist, but like other instincts, it may be mistaken and misleading. When the sceptic insists on these points, they show their strength, or rather, both their own weakness and ours. For the moment at least, the sceptic seems to destroy all certainty and conviction. These arguments could be presented at greater length if any lasting good or benefit to society could ever be expected from them.

128. For here is the chief and most confounding objection to excessive scepticism, that no durable good can ever result from it; while it remains in its full force and vigour. We need only ask such a sceptic, What his meaning is? And what he proposes by all these curious researches? He is immediately at a loss, and knows not what to answer. A Copernican or Ptolemaic, who supports each his different system of astronomy, may hope to produce a conviction, which will remain constant and durable, with his audience. A Stoic or Epicurean displays principles, which may not be durable, but which have an effect on conduct and behaviour. But a Pyrrhonian cannot expect, that his philosophy will have any constant influence on the mind: or if it had, that its influence would be beneficial to society. On the contrary, he must acknowledge, if he will acknowledge anything, that all human life must perish, were his principles universally and steadily to prevail. All discourse, all action would immediately cease; and men remain in a total lethargy, till the necessities of nature, unsatisfied, put an end to their miserable existence. It is true; so fatal an event is very little to be dreaded. Nature is always too strong for principle. And though a Pyrrhonian may throw himself or others into a momentary amazement and confusion by his profound reasonings; the first and most trivial event in life will put to flight all his doubts and scruples, and leave him the same, in every point of action and speculation, with the philosophers of every other sect, or with those who never concerned themselves in any philosophical researches. When he awakes from his dream, he will be the first to join in the laugh against himself, and to confess, that all his objections are mere amusement, and can have no other tendency than to show the whimsical condition of mankind, who must act and reason and believe; though they are not able, by their most diligent enquiry, to satisfy themselves concerning the foundation of these operations, or to remove the objections, which may be raised against them.

128. The chief and most devastating objection to excessive scepticism is that it can never produce any lasting good while it remains at full strength. We need only ask such a sceptic, What does he mean? And what does he hope to achieve by all these elaborate investigations? He is immediately at a loss and does not know how to answer. A Copernican or Ptolemaic astronomer, each defending a different system of astronomy, may hope to convince an audience in a lasting way. A Stoic or Epicurean presents principles that may not last but do affect conduct and behaviour. But a Pyrrhonian cannot expect his philosophy to have any lasting influence on the mind. Nor, if it did, could he expect its influence to benefit society. On the contrary, he must admit, if he admits anything, that all human life would perish if his principles were universally and consistently followed. All conversation and action would immediately cease. People would remain completely inactive until their unmet natural needs put an end to their miserable existence. It is true that we have little reason to fear such a fatal outcome. Nature is always stronger than principle. A Pyrrhonian may briefly bewilder and confuse himself or others with his profound reasoning. But the first and most trivial event in life will drive away all his doubts and misgivings. In everything he does and thinks, he will be just like philosophers of every other school, or people who have never concerned themselves with philosophy. When he wakes from his dream, he will be the first to laugh at himself. He will admit that all his objections are merely a form of amusement. Their only possible effect is to show the strange condition of human beings. We must act, reason, and believe, though even our most careful inquiry cannot satisfy us about the foundations of these activities. Nor can it remove the objections that may be raised against them.

129. There is, indeed, a more mitigated scepticism or academical philosophy, which may be both durable and useful, and which may, in part, be the result of this Pyrrhonism, or excessive scepticism, when its undistinguished doubts are, in some measure, corrected by common sense and reflection. The greater part of mankind are naturally apt to be affirmative and dogmatical in their opinions; and while they see objects only on one side, and have no idea of any counterpoising argument, they throw themselves precipitately into the principles, to which they are inclined; nor have they any indulgence for those who entertain opposite sentiments. To hesitate or balance perplexes their understanding, checks their passion, and suspends their action. They are, therefore, impatient till they escape from a state, which to them is so uneasy: and they think, that they could never remove themselves far enough from it, by the violence of their affirmations and obstinacy of their belief. But could such dogmatical reasoners become sensible of the strange infirmities of human understanding, even in its most perfect state, and when most accurate and cautious in its determinations; such a reflection would naturally inspire them with more modesty and reserve, and diminish their fond opinion of themselves, and their prejudice against antagonists. The illiterate may reflect on the disposition of the learned, who, amidst all the advantages of study and reflection, are commonly still diffident in their determinations: and if any of the learned be inclined, from their natural temper, to haughtiness and obstinacy, a small tincture of Pyrrhonism might abate their pride, by showing them, that the few advantages, which they may have attained over their fellows, are but inconsiderable, if compared with the universal perplexity and confusion, which is inherent in human nature. In general, there is a degree of doubt, and caution, and modesty, which, in all kinds of scrutiny and decision, ought for ever to accompany a just reasoner.

129. There is, however, a more moderate scepticism, or Academic philosophy, which may be both lasting and useful. It may arise partly from Pyrrhonism, or excessive scepticism, when common sense and reflection partly correct its doubts about everything. Most people are naturally inclined to be assertive and dogmatic in their opinions. They see things only from one side and have no idea of any argument against their view. So they rush into the beliefs they are inclined to accept. They also show no tolerance for those who hold opposing views. Hesitating or weighing alternatives confuses their understanding, restrains their passion, and delays their action. They are therefore impatient to escape this uncomfortable state. They think they can never get far enough away from it by asserting their views forcefully and holding to them stubbornly. But suppose such dogmatic thinkers became aware of the strange weaknesses of human understanding, even at its best. These weaknesses persist even when our judgments are most careful and cautious. Reflecting on them would naturally make such thinkers more modest and reserved. It would also lessen their high opinion of themselves and their prejudice against their opponents. Those without formal education may reflect on the attitude of learned people. Despite all the advantages of study and reflection, learned people are still usually hesitant in their judgments. And some learned people may be naturally inclined to arrogance and stubbornness. A small dose of Pyrrhonism might lessen their pride. It could show them how slight their few advantages over others are. These advantages are slight compared with the perplexity and confusion common to all human beings. In general, a sound thinker ought always to show some doubt, caution, and modesty in every kind of inquiry and decision.

130. Another species of mitigated scepticism which may be of advantage to mankind, and which may be the natural result of the Pyrrhonian doubts and scruples, is the limitation of our enquiries to such subjects as are best adapted to the narrow capacity of human understanding. The imagination of man is naturally sublime, delighted with whatever is remote and extraordinary, and running, without control, into the most distant parts of space and time in order to avoid the objects, which custom has rendered too familiar to it. A correct Judgement observes a contrary method, and avoiding all distant and high enquiries, confines itself to common life, and to such subjects as fall under daily practice and experience; leaving the more sublime topics to the embellishment of poets and orators, or to the arts of priests and politicians. To bring us to so salutary a determination, nothing can be more serviceable, than to be once thoroughly convinced of the force of the Pyrrhonian doubt, and of the impossibility, that anything, but the strong power of natural instinct, could free us from it. Those who have a propensity to philosophy, will still continue their researches; because they reflect, that, besides the immediate pleasure, attending such an occupation, philosophical decisions are nothing but the reflections of common life, methodized and corrected. But they will never be tempted to go beyond common life, so long as they consider the imperfection of those faculties which they employ, their narrow reach, and their inaccurate operations. While we cannot give a satisfactory reason, why we believe, after a thousand experiments, that a stone will fall, or fire burn; can we ever satisfy ourselves concerning any determination, which we may form, with regard to the origin of worlds, and the situation of nature, from, and to eternity?

130. Another kind of moderate scepticism may benefit humanity. It may also arise naturally from Pyrrhonian doubts and misgivings. This scepticism limits our inquiries to subjects best suited to the narrow capacity of human understanding. The human imagination naturally delights in grand, distant, and extraordinary things. It roams freely through the farthest reaches of space and time, avoiding things that habit has made too familiar. Sound judgment takes the opposite approach. It avoids distant and lofty inquiries and confines itself to everyday life and to subjects within our daily practice and experience. It leaves grander subjects to the embellishments of poets and orators, or to the arts of priests and politicians. To bring us to this beneficial decision, nothing is more useful than a thorough conviction of the force of Pyrrhonian doubt. We must also be convinced that nothing but the strong power of natural instinct could free us from it. People inclined toward philosophy will still continue their research. They recognize that, besides giving immediate pleasure, philosophy produces conclusions that are simply the reflections of everyday life, organized and corrected. But they will never be tempted to go beyond everyday life as long as they consider the limitations of their faculties. Those faculties have a narrow reach and work imprecisely. Even after a thousand experiments, we cannot give a satisfactory reason for believing that a stone will fall or fire will burn. Can we then ever satisfy ourselves about any conclusion we reach concerning the origin of worlds and the state of nature throughout eternity, past and future?

This narrow limitation, indeed, of our enquiries, is, in every respect, so reasonable, that it suffices to make the slightest examination into the natural powers of the human mind and to compare them with their objects, in order to recommend it to us. We shall then find what are the proper subjects of science and enquiry.

This narrow limit on our inquiries is indeed reasonable in every respect. We need only briefly examine the natural powers of the human mind and compare them with the subjects of inquiry. This is enough to show us why we should accept the limit. We will then discover the proper subjects of science and inquiry.

131. It seems to me, that the only objects of the abstract science or of demonstration are quantity and number, and that all attempts to extend this more perfect species of knowledge beyond these bounds are mere sophistry and illusion. As the component parts of quantity and number are entirely similar, their relations become intricate and involved; and nothing can be more curious, as well as useful, than to trace, by a variety of mediums, their equality or inequality, through their different appearances. But as all other ideas are clearly distinct and different from each other, we can never advance farther, by our utmost scrutiny, than to observe this diversity, and, by an obvious reflection, pronounce one thing not to be another. Or if there be any difficulty in these decisions, it proceeds entirely from the undeterminate meaning of words, which is corrected by juster definitions. That the square of the hypothenuse is equal to the squares of the other two sides, cannot be known, let the terms be ever so exactly defined, without a train of reasoning and enquiry. But to convince us of this proposition, that where there is no property, there can be no injustice, it is only necessary to define the terms, and explain injustice to be a violation of property. This proposition is, indeed, nothing but a more imperfect definition. It is the same case with all those pretended syllogistical reasonings, which may be found in every other branch of learning, except the sciences of quantity and number; and these may safely, I think, be pronounced the only proper objects of knowledge and demonstration.

131. It seems to me that quantity and number are the only proper subjects of abstract science, or demonstration. All attempts to extend this more perfect kind of knowledge beyond those limits are mere sophistry and illusion. The parts of quantities and numbers are entirely alike, so their relations become intricate and complicated. Nothing can be more fascinating or useful than tracing their equality or inequality through their different appearances. We do this by various intermediate steps. But all other ideas are clearly distinct and different from one another. However closely we examine them, we can only observe this diversity and recognize that one thing is not another. If there is any difficulty in making these judgments, it comes entirely from the uncertain meanings of words. More precise definitions correct this problem. Consider the proposition that the square of the hypotenuse is equal to the squares of the other two sides. However precisely we define the terms, we cannot know it without a series of arguments and inquiries. But consider the proposition that where there is no property, there can be no injustice. To convince us of this, we need only define the terms and explain injustice as a violation of property. This proposition is really only a less precise definition. The same is true of all the supposed syllogistic reasoning found in every other branch of learning, except the sciences of quantity and number. I think we can safely say that quantity and number are the only proper subjects of knowledge and demonstration.

132. All other enquiries of men regard only matter of fact and existence; and these are evidently incapable of demonstration. Whatever is may not be. No negation of a fact can involve a contradiction. The non-existence of any being, without exception, is as clear and distinct an idea as its existence. The proposition, which affirms it not to be, however false, is no less conceivable and intelligible, than that which affirms it to be. The case is different with the sciences, properly so called. Every proposition, which is not true, is there confused and unintelligible. That the cube root of 64 is equal to the half of 10, is a false proposition, and can never be distinctly conceived. But that Caesar, or the angel Gabriel, or any being never existed, may be a false proposition, but still is perfectly conceivable, and implies no contradiction.

132. All other human inquiries concern only matters of fact and existence. These clearly cannot be demonstrated. Whatever is may not be. Denying a fact can never involve a contradiction. The idea that any being does not exist is as clear and distinct as the idea that it exists. The statement that a being does not exist, however false, is just as conceivable and understandable as the statement that it exists. The case is different in the sciences, properly so called. In those sciences, every statement that is not true is confused and unintelligible. The statement that the cube root of 64 equals half of 10 is false and can never be clearly conceived. But the statement that Caesar, the angel Gabriel, or any being never existed may be false. Even so, it is perfectly conceivable and involves no contradiction.

The existence, therefore, of any being can only be proved by arguments from its cause or its effect; and these arguments are founded entirely on experience. If we reason a priori, anything may appear able to produce anything. The falling of a pebble may, for aught we know, extinguish the sun; or the wish of a man control the planets in their orbits. It is only experience, which teaches us the nature and bounds of cause and effect, and enables us to infer the existence of one object from that of another³⁴. Such is the foundation of moral reasoning, which forms the greater part of human knowledge, and is the source of all human action and behaviour.

Therefore, the existence of any being can only be proved by arguments from its cause or its effect. These arguments are based entirely on experience. If we reason a priori, anything may seem capable of producing anything else. As far as we know, a falling pebble may put out the sun, or a man's wish may control the planets in their orbits. Only experience teaches us the nature and limits of cause and effect. It enables us to infer the existence of one object from the existence of another³⁴. This is the foundation of moral reasoning, which makes up most of human knowledge. It is also the source of all human action and behavior.

Moral reasonings are either concerning particular or general facts. All deliberations in life regard the former; as also all disquisitions in history, chronology, geography, and astronomy.

Moral reasoning concerns either particular facts or general facts. All deliberations in life concern particular facts. So do all investigations in history, chronology, geography, and astronomy.

The sciences, which treat of general facts, are politics, natural philosophy, physic, chemistry, &c. where the qualities, causes and effects of a whole species of objects are enquired into.

The sciences that study general facts include politics, natural science, medicine, and chemistry. They examine the qualities, causes, and effects of whole classes of objects.

Divinity or Theology, as it proves the existence of a Deity, and the immortality of souls, is composed partly of reasonings concerning particular, partly concerning general facts. It has a foundation in reason, so far as it is supported by experience. But its best and most solid foundation is faith and divine revelation.

Divinity, or theology, seeks to prove that God exists and that souls are immortal. It does so through reasoning about particular facts and general facts. Theology has a foundation in reason insofar as experience supports it. But its best and strongest foundation is faith and divine revelation.

Morals and criticism are not so properly objects of the understanding as of taste and sentiment. Beauty, whether moral or natural, is felt, more properly than perceived. Or if we reason concerning it, and endeavour to fix its standard, we regard a new fact, to wit, the general tastes of mankind, or some such fact, which may be the object of reasoning and enquiry.

Morality and criticism are matters of taste and feeling rather than understanding. Beauty, whether moral or natural, is felt rather than perceived. Or, if we reason about beauty and try to establish a standard for it, we consider a different fact. This might be the general tastes of humanity or some similar fact that can be reasoned about and investigated.

When we run over libraries, persuaded of these principles, what havoc must we make? If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: for it can contain nothing but sophistry and illusion.

When we go through libraries convinced of these principles, what destruction we must cause! Suppose we pick up a book on theology or scholastic metaphysics, for example. Let us ask: Does it contain any abstract reasoning about quantity or number? No. Does it contain any reasoning based on experience about matters of fact and existence? No. Then throw the book into the flames, because it can contain nothing but sophistry and illusion.