The Proemium of St. Thomas to Aristotle’s Posterior Analytics
Translated by Anthony Andres
1. As Aristotle says in the beginning of his Metaphysics, the family of men live by art and reasons. In this the Philosopher seems to touch on something that is man’s own, something by which he differs from the rest of the animals. This is so because, while the other animals are driven to their actions by a certain natural instinct, man is directed in his actions by the judgement of reason. And so it is that the various arts serve to perfect human actions easily and in an orderly way. In fact we see that art is nothing but a sure, rational ordering of the way human actions arrive at their correct end through determinate means.
Reason not only can direct the actions of the lower parts, but it also directs its own actions, because it belongs to the understanding part to reflect upon itself. Indeed, the understanding understands itself, and in the same way reason can reason about itself. Therefore, if the arts of building and making, through which man can do such actions easily and in an orderly way, were discovered because reason reasoned about the actions of the hands, for the same reason there must be some art which directs the actions of reason itself. Through this, man proceeds in the actions of reason in an orderly manner, easily, and without error.
2. This art is Logic, that is, the rational science. This is not only rational because it accords with reason (this is common to all the arts), but also because it is about the actions of reason as about its own matter.
3. We see, therefore, that it is the art of arts, since it directs the actions of reason from which all of the arts come. Therefore we must take the parts of logic from the variety in the actions of reason.
4. Now there are three actions of reason. The first two belong to reason insofar as it is a kind of understanding.
One action of the understanding is the understanding of what is not complex and cannot be divided, which understanding conceives what a thing is. This operation is called by some the informing of the understanding, or imagining through understanding. The teaching which Aristotle gives in the book Categories is ordered to this operation of reason.
The second operation of the understanding is the composing and dividing of understanding, in which we first find the true and the false. The teaching which Aristotle gives in the book On Interpretation (Peri Hermeneias) aids this action of reason.
The third action of reason deals with what belongs only to reason, namely, discoursing from one thing into another, so that from what is known it comes to a knowledge of what was unknown. The rest of the books of Logic aid this action.
5. Notice that, in a certain way, the actions of reason are like the actions of nature. That is why art imitates nature as much as it can. Now we find three kinds of actions in nature. In certain things nature acts by necessity, that is, in such a way that she cannot fail. In other things nature works more frequently than not, although sometimes she falls short of her proper action. There must be two kinds of actions in the latter case: one which happens for the most part, as when a complete animal is born from the seed; the other, as when nature falls short of what is fitting, as when a monstrosity is born from the seed because of the corruption of some principle.
These three are also found in the actions of reason. One process of reason produces necessity, so that there is no possibility of falling short of the truth. We acquire the certainty of science in this process. There is another process of reason which concludes to the truth for the most part but not with necessity. The third process of reason is that in which reason falls short of the truth because of a failure to follow some principle in reasoning.
6. The part of Logic which aids the first process is called the Judging part because judgement has the certainty of science. Since we cannot have sure judgement of effects unless we resolve them into first principles, this part of logic is called Analytic, which means resolving. The certainty of judgment that we possess through resolving comes from either: the form of the syllogism alone, and the book Prior Analytics, which is about the syllogism considered simply, is ordered to this; or also from the matter, when essential and necessary propositions are taken, and the book Posterior Analytics, which is about the demonstrative syllogism, is ordered to this.
Another part of Logic, called the Discovering part, aids the second process of reason. It is called Discovering because discovery does not always possess certainty. Thus, in order to acquire certainty we need to make a judgement about what has been discovered. Now just as we notice a kind of gradation in natural things which act for the most part (since the stronger the natural power, the less often it fails to produce its effect), so also we find some gradation in the process of reason that is not entirely certain. The process of reason has that gradation insofar as it approaches more and less to perfect certainty.
Sometimes although such a process does not produce science, it does produce belief or opinion because of the probability of the propositions from which it proceeds. For reason inclines toward one side of a contradiction completely, although a fear of the other side remains. Topics or dialectics is ordered to this because the dialectical syllogism, which Aristotle discusses in the book Topics, proceeds from probable.
Sometimes it produces, not complete belief or opinion, but a kind of suspicion, since it does not incline entirely toward one side of a contradiction, although more into one side than the other. The Rhetoric is ordered to this.
Sometimes only an estimation inclines into one side of a contradiction. This happens because of some representation, of the kind in which some food might become abominable to a man if it was represented in the appearance of something abominable. The Poetics is ordered to this, since it is characteristic of the poet to lead us toward something virtuous through a decent representation.
All of these pertain to rational philosophy because it is characteristic of reason to lead from one thing into another.
The third part of logic, which is called sophistic and which Aristotle treats in the book Sophistical Refutations, aids the third process of reason.