Part 12

There are four senses in which one thing can be said to be 'prior' to another. Primarily and most properly the term has reference to time: in this sense the word is used to indicate that one thing is older or more ancient than another, for the expressions 'older' and 'more ancient' imply greater length of time.

One thing can be called 'prior' to another in four senses. The first and most proper sense refers to time. In this sense, the word means that one thing is older or more ancient than another. This is because 'older' and 'more ancient' imply a greater length of time.

Secondly, one thing is said to be 'prior' to another when the sequence of their being cannot be reversed. In this sense 'one' is 'prior' to 'two'. For if 'two' exists, it follows directly that 'one' must exist, but if 'one' exists, it does not follow necessarily that 'two' exists: thus the sequence subsisting cannot be reversed. It is agreed, then, that when the sequence of two things cannot be reversed, then that one on which the other depends is called 'prior' to that other.

Secondly, one thing is called 'prior' to another when their existence implies a dependence that works only one way. In this sense, 'one' is 'prior' to 'two'. For if 'two' exists, 'one' must also exist. But if 'one' exists, 'two' does not necessarily exist. So the dependence works only one way. It is agreed, then, that when dependence works only one way, the thing the other depends on is called 'prior'.

In the third place, the term 'prior' is used with reference to any order, as in the case of science and of oratory. For in sciences which use demonstration there is that which is prior and that which is posterior in order; in geometry, the elements are prior to the propositions; in reading and writing, the letters of the alphabet are prior to the syllables. Similarly, in the case of speeches, the exordium is prior in order to the narrative.

Third, the term 'prior' refers to position in any order, as in science and public speaking. For in sciences that use proofs, some things come earlier and others later in order. In geometry, the basic elements come before the propositions. In reading and writing, the letters of the alphabet come before syllables. Similarly, in speeches, the introduction comes before the narrative.

Besides these senses of the word, there is a fourth. That which is better and more honourable is said to have a natural priority. In common parlance men speak of those whom they honour and love as 'coming first' with them. This sense of the word is perhaps the most far-fetched.

Besides these meanings of the word, there is a fourth. What is better and more worthy of honour is said to come first by nature. In everyday speech, people describe those they honour and love as 'coming first' for them. This meaning of the word is perhaps the most far-fetched.

Such, then, are the different senses in which the term 'prior' is used.

These, then, are the different meanings of the term 'prior'.

Yet it would seem that besides those mentioned there is yet another. For in those things, the being of each of which implies that of the other, that which is in any way the cause may reasonably be said to be by nature 'prior' to the effect. It is plain that there are instances of this. The fact of the being of a man carries with it the truth of the proposition that he is, and the implication is reciprocal: for if a man is, the proposition wherein we allege that he is true, and conversely, if the proposition wherein we allege that he is true, then he is. The true proposition, however, is in no way the cause of the being of the man, but the fact of the man's being does seem somehow to be the cause of the truth of the proposition, for the truth or falsity of the proposition depends on the fact of the man's being or not being.

Yet there seems to be another kind of priority besides those already mentioned. Consider two things whose existence each implies the existence of the other. If one is in any way the cause of the other, it may reasonably be called naturally 'prior' to its effect. There are clear examples of this. A man's existence implies that the statement that he exists is true, and the implication works both ways. For if a man exists, the statement that he exists is true. Conversely, if the statement that he exists is true, then he exists. Yet the true statement is in no way the cause of the man's existence. Rather, the man's existence does seem somehow to cause the statement to be true. For the statement's truth or falsity depends on whether the man exists or not.

Thus the word 'prior' may be used in five senses.

So the word 'prior' may be used in five ways.