Commentary Aristotle Posterior Analytics
Lecture 44
Science compared with other modes of knowing
b30. Scientific knowledge and its object differ from opinion and the object of opinion b31. in that scientific knowledge is commensurately universal and proceeds by necessary connexions, and that which is necessary cannot be otherwise.
b33. So though there are things which are true and real and yet can be otherwise, scientific knowledge clearly does not concern them: if it did, things which can be otherwise would be incapable of being otherwise. Nor are they any concern of rational intuition — by rational intuition I mean an originative source of scientific knowledge — nor of indemonstrable knowledge, which is the grasping of the immediate premise. Since then rational intuition, science, and opinion, and what is revealed by these terms, are the only things that can be ‘true’, it follows that it is opinion that is concerned with that which may be true or false, and can be otherwise: opinion in fact is the grasp of a premise which is immediate but not necessary.
a5. This view also fits the observed facts, for opinion is unstable, and so is the kind of being we have described as its object.
a7. Besides, when a man thinks a truth incapable of being otherwise he always thinks that he knows it, never that he opines it. He thinks that he opines when he thinks that a connexion, though actually so, may quite easily be otherwise; for he believes that such is the proper object of opinion, while the necessary is the object of knowledge.
a11. In what sense, then, can the same thing be the object of both opinion and knowledge? And if any one chooses to maintain that all that he knows he can also opine, why should not opinion be knowledge? For he that knows and he that opines will follow the same train of thought through the same middle terms until the immediate premises are reached; because it is possible to opine not only the fact but also the reasoned fact, and the reason is the middle term;
a16. so that, since the former knows, he that opines also has knowledge. The truth perhaps is that if a man grasp truths that cannot be other than they are, in the way in which he grasps the definitions through which demonstrations take place, he will have not opinion but knowledge: if on the other hand he apprehends these attributes as inhering in their subjects, but not in virtue of the subjects’ substance and essential nature, possesses opinion and not genuine knowledge; and his opinion, if obtained through immediate premises, will be both of the fact and of the reasoned fact; if not so obtained, of the fact alone.
a23. The object of opinion and knowledge is not quite identical; it is only in a sense identical, just as the object of true and false opinion is in a sense identical. The sense in which some maintain that true and false opinion can have the same object leads them to embrace many strange doctrines, particularly the doctrine that what a man opines falsely he does not opine at all. There are really many senses of ‘identical’, and in one sense the object of true and false opinion can be the same, in another it cannot. Thus, to have a true opinion that the diagonal is commensurate with the side would be absurd: but because the diagonal with which they are both concerned is the same, the two opinions have objects so far the same: on the other hand, as regards their essential definable nature these objects differ. The identity of the objects of knowledge and opinion is similar. Knowledge is the apprehension of, e.g., the attribute ‘animal’ as incapable of being otherwise, opinion the apprehension of ‘animal’ as capable of being otherwise — e.g., the apprehension that animal is an element in the essential nature of man is knowledge; the apprehension of animal as predicable of man but not as an element in man’s essential nature is opinion: man is the subject in both judgements, but the mode of inherence differs. This also shows that one cannot opine and know the same thing simultaneously; for then one would apprehend the same thing as both capable and incapable of being otherwise — an impossibility. Knowledge and opinion of the same thing can co-exist in two different people in the sense we have explained, but not simultaneously in the same person. That would involve a man’s simultaneously apprehending, e.g., (1) that man is essentially animal — that is, cannot be other than animal — and (2) that man is not essentially animal, that is, we may assume, may be other than animal.
Further consideration of modes of thinking and their distribution under the heads of discursive thought, intuition, science, art, practical wisdom, and metaphysical thinking, belongs rather partly to natural science, partly to moral philosophy.
b6. Quick wit is a faculty of hitting upon the middle term instantaneously. It would be exemplified by a man who saw that the moon has her bright side always turned towards the sun, and quickly grasped the cause of this, namely that she borrows her light from him; or observed somebody in conversation with a man of wealth and divined that he was borrowing money, or that the friendship of these people sprang from a common enmity. In all these instances he has seen the major and minor terms and then grasped the causes, the middle terms. Let A represent ‘bright side turned sunward’, B ‘lighted from the sun’, C the moon. Then B, ‘lighted from the sun’ is predicable of C, the moon, and A, ‘having her bright side towards the source of her light’, is predicable of B. So A is predicable of C through B.
Scientific knowledge and its object. After comparing sciences with one another from the viewpoints of certitude, of unity and of diversity, the Philosopher here compares science to everything else that pertains to knowledge.
And his treatment falls into two parts.
In the first he treats of the comparison of science to opinion, which bears on the true and false.
In the second, of the comparison of science to those habits of knowledge which are concerned exclusively with the true, at: further consideration of modes (90a23; [405]).
The first part is divided into two parts.
In the first he determines the truth.
In the second he excludes a doubt, at: in what sense, then (90a11; [402]).
Concerning the first he does three things.
First, he lays down the difference between science and opinion.
Second, he shows what pertains to science, at: in that scientific knowledge (89b31; [396]).
Third, what pertains to opinion, at: so though there are things (89b33; [397]).
He says therefore first (89b30) that science differs from opinion; in like manner the scientifically knowable, which is the object of science, differs from the opinable, which is the object of opinion.
Then he shows what pertains to science, setting down two things which pertain to it, at: in that scientific knowledge (89b31).
One of these is that it is of the universal, for science is not concerned with singulars which fall under sense. (He explained this above). The other is that science is obtained in virtue of necessary things. And he explains that the necessary is that which cannot be otherwise. This, too, was explained above, namely, that demonstration proceeds from necessary things.
Then he shows what pertains to opinion, namely, that it is concerned with things that could be otherwise, either universally or particularly, at: so though there are things (89b33).
This he proves in three ways.