tralia were discovered it was necessary either to eliminate the component 'white' from the concept 'swan' (as was actually done) or else to create a new concept for the bird which resembled a swan, but was black. Which course is decided upon is to a great extent arbitrary, and determined by considerations of fitness.
We have then two factors participating in the formation of a concept, one objective, the result of experience; and one subjective, dictated by fitness. The fitness of a concept is adaptation to the purpose to which it is to be put, and it is this case that we must now consider.
The purpose of a concept is its application in prediction. Ancient logic established the syllogism as the type of the process of thinking, the simplest example of which is the familiar:
All men are mortal;
Cajus is a man;
Therefore, Cajus is mortal.
The universal formula,is:
To the concept M belongs the component B;
C is included in the concept M;
Therefore the component B is found in C.
It may be said that this method of reasoning has remained in use up to the present day. We must, to be sure, add that its application is of a sort quite different from its ancient one. While formerly propounding the major premise was considered the more important, and the propounding of the minor premises was regarded as an almost self-evident and easy matter, to-day the relations have been reversed. The major premise contains the description of a concept, the minor makes the assertion that a certain thing must be classed under this concept. What justification is there for such an assertion?
The most evident answer is that because all the components of the concept M (including B) are to be found in C, C must be classed under the concept M. A conclusion of this kind would certainly be true, but at the same time quite valueless, for it only repeats the assertion of the minor premise.
As a matter of fact, our method of drawing conclusions is essentially different, for the minor premise is not obtained by proving all the constituents of the concept M to be present in C; but only some of them. The conclusion is, therefore, not binding, but merely probable. The whole method of drawing a conclusion is as follows: Certain constituents frequently occur together. They are combined to form the concept M. In the thing C some of the constituents may be recognized. Therefore, presumably the other components of the concept M occur in C.
