ABC
aBc
abC
abc.
For the description of the class C we have
C = ABC ꖌ abC,
that is, “a rectilinear figure is either a triangle and three-sided, or not a triangle and not three-sided.”
For the class b we have
b = abC ꖌ abc.
To the second side of this we may apply the process of simplification by abstraction described in the last section; for by the Law of Duality
ab = abC ꖌ abc;
and as we have two propositions identical in the second side of each we may substitute, getting
b = ab,