| AbC | aBc |
| Abc | abC |
| abc. |
Selecting the combinations which contain A, we find the description of granite to be
A = AbC ꖌ Abc = Ab(C ꖌ c),
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
C = AbC ꖌ abC = bC(A ꖌ a),
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])
| All planets are subject to gravity, | (1) |
| Fixed stars are not planets. | (2) |
The false conclusion is that “fixed stars are not subject to gravity.” The terms are
A = planet
B = fixed star
C = subject to gravity.