Inconsistent triad

An inconsistent triad consists of three propositions of which at most two can be true.

For example: If one finds oneself believing all three propositions of an inconsistent triad, then (in order to be rational) one must give up or modify at least one of those beliefs.

Any inconsistent triad {A, B, C} gives rise to a trilemma {{A, B}, {B, C}, {C, A}}.

The dialectical framework for the whole discussion of the problem in the philosophy of perception and the theoretical conception of perceptual experience is set out as an inconsistent triad.

[1] The first proposition is defended by realists, while being rejected by anti-realists or idealists.