CHAPTER VI. THE INDIRECT METHOD OF INFERENCE.

ordinary discussion. Let us take the example of a fallacious argument, previously treated by the Method of Direct Inference (p.

and let us ascertain whether any precise conclusion can be drawn concerning the relation of granite and basalt. Taking as before

the premises become

Of the eight conceivable combinations of A, B, C, five agree with these conditions, namely

Selecting the combinations which contain A, we find the description of granite to be

that is, granite is not a sedimentary rock, and is either basalt or not-basalt. If we want a description of basalt the answer is of like form

that is basalt is not a sedimentary rock, and is either granite or not-granite. As it is already perfectly evident that basalt must be either granite or not, and vice versâ, the premises fail to give us any information on the point, that is to say the Method of Indirect Inference saves us from falling into any fallacious conclusions. This example sufficiently illustrates both the fallacy of Negative premises and that of Undistributed Middle of the old logic.

The fallacy called the Illicit Process of the Major Term is also incapable of commission in following the rules of the method. Our example was (p. 65)

The false conclusion