Commentary Aristotle Posterior Analytics
First, by way of a division, saying that in addition to necessary truths, which cannot be otherwise, there are non-necessary truths, which could be otherwise. Now, from what has been said above, it is clear that science is not concerned with the latter, because it would follow that contingent things would be such as could not be otherwise. For science is concerned with such things, as has been said. Similarly, it cannot be said that understanding is concerned with them. “Understanding” is taken here not as a faculty [power] of the soul, but as being the principle of science, that is, as the habit of first principles, from which demonstration proceeds in causing science. Hence in explaining what that understanding is which is the principle of science he adds, “Nor of indemonstrable knowledge” (88b37), that is, not of facts that could be otherwise. As if to say: understanding is nothing more than a science of the indemonstrable. For just as science implies certainty of knowledge acquired through demonstration, so understanding implies certitude of knowledge without demonstration; not because of a shortcoming in some demonstration, but because that about which this certainty is had, is indemonstrable and per se known. Therefore, to explain this he adds that demonstrative science is nothing else than the certain intuition of an immediate proposition. But that understanding is science of the indemonstrable is clear from the fact that he says that it is "the principle of science". For since science is concerned with the necessary, and the necessary is not concluded except from the necessary, as has been proved above, it is required that understanding, which is the principle of science, not be concerned with contingent things.
Having shown, therefore, that neither science nor understanding is concerned with contingent things, he sets down a division and says that understanding and science and opinion happen to be true as that does which is stated by them, that is, which is verbally stated by understanding and science and true opinion. For the true is found both in the intellect’s act of composing and dividing and in the outward expression of this act insofar as it signifies the inward truth of the opinion or science or understanding. Therefore, if every truth belongs either to understanding or science or opinion, and there are some contingent truths, and they belong neither to science nor understanding, what is left is that opinion is concerned with them, whether they be actually true or actually false, provided that they could be other than they are.
In order to elucidate what opinion is, he adds that opinion is the acceptance, that is, the grasping, of a proposition that is immediate and not necessary. And this can be understood in two ways: in one way, so that the immediate proposition in itself is indeed necessary, but it is accepted by opinion as non-necessary; in another way, so that it is in itself contingent. For an immediate proposition is one that cannot be proved through a middle, whether it be a necessary proposition or not. For it has been shown above that there is no process to infinity in predications, neither on the part of the middles nor on the part of the extremes. And this was shown not only analytically in demonstrations, but also logically in general as to syllogisms. Therefore, if there be a contingent proposition which is mediate, it must be reduced to others that are immediate. However, it is not reduced to necessary immediate propositions, because necessary things are not the proper principles of contingent things, nor can contingent things be concluded from necessary things. Hence what remains is that some contingent propositions are immediate and some mediate. Thus, “The man does not run,” is mediate, for it can be proved through this middle, “The man is not in motion,” which is also contingent, albeit immediate. The acceptance of such immediate contingent propositions is opinion. Yet this does not mean that the accepting of a mediate contingent proposition is not opinion. For opinion is related to contingent things, as science and understanding to necessary things.
Second, he proves the same point by means of that which is commonly observed, at: this view also fits (90a5).
He says that what has been said, mainly, that opinion is concerned with the contingent is confessed, that is, in agreement with things that are observed. For opinion seems to denote something weak and uncertain and to be of such a nature that weakness and uncertainty are in it.
Third, he proves the same point by experiment, at: besides, when a man (90a7).
For no one, when he thinks that it is impossible for a thing to be otherwise, supposes that he is forming an opinion; rather he considers himself to know scientifically. But when he thinks that something is so and that there is nothing to prevent its being otherwise, then it is that he considers himself to have opinions. This would indicate that opinion concerns such things, that is, contingent things, but science necessary things.
Then he raises a doubt concerning the aforesaid, at: in what sense, then (90a11).
First, he raises the doubts.
Second, he solves them, at: so that, since the former (90a16; [403]).
Concerning the first (90a11), he presents two doubts.
One of these is concerned with the opinable and the scientifically knowable. If opinion is concerned with the contingent and science with the necessary, and the contingent is not the same as the necessary, a doubt remains as to how a man can opine and scientifically know the same thing.
The second doubt concerns science and opinion, namely, why opinion is not science; supposing, of course, that one claims that there can be opinion about every known thing. For in regard to everything known a man can opine that it could be otherwise (except perhaps in the case of first principles per se known, whose contraries cannot be conceived, and concerning which there is not science but understanding). But in regard to all mediate truths of which there is demonstration and science, someone can suppose that it is possible that they could be otherwise. Consequently, they can fall under opinion. For opinion is not concerned exclusively with things contingent in their very nature, because then a man could not have opinion about everything he knows. Rather, opinion is concerned with that which is accepted as possible to be otherwise, whether it is that or not. Therefore, on this supposition, it remains that science and opinion are the same, because both the scientific knower and the man of opinion acquire science and opinion through middles until they reach things which are immediate, as is clear from the foregoing. Hence if someone proceeds through middles to immediate propositions he has science. Now, this is what the man of opinion does, because just as it is possible to have an opinion 'that' something is so, it is also possible to have an opinion 'why' something is so. But when I say, 'why', a middle is implied. Hence it is clear that opinion can proceed to immediates through a middle, whether opinion be of things that are contingent in their very nature, or of things accepted as contingent.
Then he solves the aforesaid doubts, at: so that, since the former (90a16).
First, he solves the second one which is concerned with the identity of science and opinion.
Second, he solves the first one which is concerned with the identity of the scientifically knowable and the opinable, at: the object of opinion (90a23; [404]).
He says therefore first (90a16) that if someone proceeds through middles to immediates in such a way that the middles are not considered capable of being otherwise, but are considered to behave as definitions which are the middles through which demonstrations proceed, there will not be opinion but science. But if someone proceeds to the immediates through certain true middles which, nevertheless, are either not verified of the things of which they are said per se (as definitions which are predicated essentially or signify the species of a thing)—or he does not take them as being in these things per se, then he will have opinion and will not truly know the 'quia' and the 'propter quid' at once, even if he proceeds as far as the immediates: for then he will be forming an opinion through the immediates and will not know scientifically. But if he does not proceed through immediates but through mediates, then he will not be forming an opinion bearing on the 'propter quid' but only the 'quia'. For even scientific knowledge, when it is not propter quid and immediate, is not 'propter quid' science but 'quia'.
Then he solves the first doubt which concerns the identity of the scientifically known and the object of opinion, at: the object of opinion (90a23).