 The book is also not without some self-deprecating humour. As Blackwell points out (2011: 158, 160), the authors twice poke fun at the length and tedium of the project’s many logical derivations. In Volume I, the authors explain that one cannot list all the non-intensional functions of \(\phi \bang \hat{z}\) “because life is too short” (1910 [1925: 73]); and in Volume 3, after over 1,800 pages of dense symbolism, the authors end Part IV, Section D, on Cyclic Families, with the comment,