I discuss a collection of problems in relevance logic. The main problems discussed are: the decidability of the positive semilattice system, decidability of the fragments of R in a restricted number of variables, and the complexity of the decision problem for the implicational fragment of R. Some related problems are discussed along the way.

Except for its belated proof of 1 + 1 = 2, Principia Mathematica doesn’t feature in studies of mathematical humour. Yet there is restrained and understated humour in that work, despite the inauspicious conditions under which it was written. Russell, to take one of the authors, had an irrepressible talent for enlivening his subject matter. This paper explores even the "obscure corners" of PM to uncover its humour and wit, which, for non-logicians, can be an entree to the work.