In one of his better-known essays, "Between Left and Right: A Non-Euclidean Perspective," (reprinted in Email to the Universe), Robert Anton Wilson offers this formula of "maybe logic":
"In modern mathematics and logic, in addition to the two-valued (yes/no) logic of Aristotle and Boole, there are several three-valued logics (e.g. the yes, no and maybe Quantum Logic of von Neumann; the yes, no and po of psychologist Edward de Bono; etc.), at least one four-valued logic (the true, false, indeterminate and meaningless of Rapoport), and an infinite-valued logic (Korzybski). I myself have presented a multi-valued logic in my neuroscience seminars; the bare bones of this system will be found in my book, The New Inquisition. Two-valued Euclidean choices — left or right of an imaginary line — do not seem very 'real' to me, in comparison to the versatility of modern science and mathematics."
Hat tip: Raw Semantics on Twitter.
Update: Another citation.