It was developed by Layman E. Allen in 1962[1][2] a former professor of Yale Law School and the University of Michigan.
As marketed in the 1960s WFF 'N PROOF was a series of 20 games of increasing complexity, varying with the logical rules and methods available.
All players must be able to recognize a "well-formed formula" (WFF in Łukasiewicz notation), to assemble dice values into valid statements (WFFs) and to apply the rules of logical inference so as to complete a proof.
P-Flub, or Challenge Impossible means the player believes the Mover cannot make a Solution using the cubes in Required, Permitted, and Resources.
The name is a play on Whiffenpoofs,[citation needed] an a cappella singing group established at Yale University in 1909.