A = B,
we must ascertain which of these combinations will be rendered self-contradictory by substitution; the second and third will have to be struck out, and there will remain only
AB
ba.
Hence we draw the following inferences
A = AB, B = AB, a = ab, b = ab.
Exactly the same method must be followed when a question involves a greater number of terms. Thus by the Law of Duality the three terms A, B, C, give rise to eight conceivable combinations, namely
| ABC | (α) | aBC | (ε) |
| ABc | (β) | aBc | (ζ) |
| AbC | (γ) | abC | (η) |
| Abc | (δ) | abc. | (θ) |
The development of the term A is formed by the first four of these; for B we must select (α), (β), (ε), (ζ); C consists of (α), (γ), (ε), (η); b of (γ), (δ), (η), (θ), and so on.
Now if we want to investigate completely the meaning of the premises
| A = AB | (1) |
| B = BC | (2) |