C.S. Pierce's "response to the anticipated suspicion that he
attaches a superstitious or fanciful importance to the number
three, and forces divisions to a Procrustean bed of trichotomy."
"I fully admit that there is a not uncommon craze for
trichotomies. I do not know but the psychiatrists have provided a name for it. If not, they should. "Trichimania," [?]
unfortunately, happens to be preempted for a totally different
passion; but it might be called
triadomany. I am not so
afflicted; but I find myself obliged, for truth's sake, to make
such a large number of trichotomies that I could not [but] wonder if my readers, especially those of them who are in the way of
knowing how common the malady is, should suspect, or even
opine, that I am a victim of it. But I am now and here going
to convince those who are open to conviction, that it is not so,
but that there is a good reason why a thorough student of the
subject of this book should be led to make trichotomies, that
the nature of the science is such that not only is it to be expected that it should involve real trichotomies, but furthermore, that there is a cause that tends to give this form."
(Collected Papers, C.S.Peirce, Principles of Philosophy, 1.568)