Two on a Tower have done...while other eminent critics (I wonder if they are the same) print the most cutting rebukes you can conceive—show me (to my amazement) that I am quite an immoral person...” Two on a Tower Two on a Tower (1882) is a novel by English author Thomas Hardy, classified by him as a romance and fantasy and now regarded as one of his minor works. The book is one of Hardy's Wessex novels, set in a parallel version of late Victorian Dorset. Hardy placed an epigraph at the beginning of this book. The epigraph is from a Richard Crashaw poem,
S (set theory) a set "x" whose members are just those sets satisfying "A"("y"). The role of "Spec" in S is analogous to that of the axiom schema of specification of Z. Boolos’s name for Zermelo set theory minus extensionality was "Z-". Boolos derived in S all axioms of "Z-" except the axiom of choice. The purpose of this exercise was to show how most of conventional set theory can be derived from the iterative conception of set, assumed embodied in S. Extensionality does not follow from the iterative conception, and so is not a theorem of S. However, S + Extensionality is