The term A appears in the first and second; B in the first and third; *a* in the third and fourth; and *b* in the second and fourth. Now if we have any premise, say 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) *a*BC (ε) AB*c* (β) *a*B*c* (ζ) A*b*C (γ) *ab*C (η) A*bc* (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) we examine each of the eight combinations as regards each premise; (γ) and (δ) are contradicted by (1), and (β) and (ζ) by (2), so that there remain only ABC (α) *a*BC (ε) *ab*C (η) *abc*. (θ) To describe any term under the conditions of the premises (1) and (2), we have simply to draw out the proper combinations from this list; thus, A is represented only by ABC, that is to say A = ABC, similarly *c* = *abc*. For B we have two alternatives thus stated, B = ABC ꖌ *a*BC; and for *b* we have *b* = *ab*C ꖌ *abc*. When we have a problem involving four distinct terms we need to double the number of combinations, and as we add each new term the combinations become twice as numerous. Thus A, B produce four combinations A, B, C, " eight " A, B, C, D " sixteen " A, B, C, D, E " thirty-two " A, B, C, D, E, F " sixty-four " and so on.