Page:Philosophical Review Volume 13.djvu/17

in the strict sense of the term, is the knowledge of the 'cause', or of that which 'cannot be otherwise.' Now, knowledge of this kind is obtained by means of demonstration (ἀπόδειξις), or scientific syllogism, the data of which are supplied by induction. The character of those data may be deduced from the conclusions which have to be reached. If the judgments of science predicate what is necessary, the premises must be such as by a valid logical process will yield judgments of that kind. In the first place, therefore, the premises must be true. And this means that they must state what belongs to the actual nature of things; for the test of a true judgment is never in Aristotle the mere impossibility of thinking the opposite, but its conformity to the object; a judgment is true when it combines in thought what is combined in the thing, or separates in thought what is separated in the thing. The reason why the judgment, "The diagonal is commensurable," is false, is that it affirms a connection of subject and predicate which contradicts the actual nature of the diagonal. In the second place, the premises of a demonstrative syllogism must be primary or indemonstrable. For, if this is not admitted, we either fall into an infinite series, and therefore never reach an absolute conclusion, or we are forced to hold the equally untenable doctrine that nothing is true except what can be demonstrated. There must, then, Aristotle contends, be certain immediate or primary truths, which by their very nature are indemonstrable, and without which no demonstration, and therefore no science,' is possible. In the third place, our premises must contain the ground or cause. For, as we have seen, the judgments of science are in all cases necessary, or express the 'essence' or 'ground' of a thing. Hence the premises must be 'better known' than the conclusion and 'prior' to it. This does not mean that, in the order of our knowledge, we start from what is, in the sense indicated, 'better known'; on the contrary, we begin with particular perceptions of sense, and only at a latter stage advance to the universal. What we mean by saying that the premises of science are 'better known' than the conclusion, is that they contain the determination of the 'necessary' characteristics of a thing, and therefore the 'cause' or