The definition takes the form
A = BC(D ꖌ E);
but if we develop the alternatives by a method to be afterwards more fully considered, it becomes
A = BCDE ꖌ BCDe ꖌ BCdE.
An example of a still more complex proposition is found in De Morgan’s writings,[71] as follows:—“He must have been rich, and if not absolutely mad was weakness itself, subjected either to bad advice or to most unfavourable circumstances.”
If we assign the letters of the alphabet in succession, thus,
A = he
B = rich
C = absolutely mad
D = weakness itself
E = subjected to bad advice
F = subjected to most unfavourable circumstances,
the proposition will take the form
A = AB{C ꖌ D (E ꖌ F)},
and if we develop the alternatives, expressing some of the different cases which may happen, we obtain