 Thomas Aquinas held that among the things whose existence needs explanation are contingent beings that depend for their existence upon other beings. Richard Taylor (1992: 84–94) discusses the argument in terms of the world (“everything that ever does exist, except God, in case there is a god”, 1992: 87) being contingent and thus needing explanation. Arguing that the term “universe” refers to an abstract entity or set, William Rowe rephrases the issue, “Why does that set (the universe) have the members that it does rather than some other members or none at all?” (Rowe 1975: 136). Put broadly, “Why is there anything at all?” (Smart, in Smart and Haldane, 1996: 35; Rundle 2004). The response of defenders of the cosmological argument is that what is contingent exists because of some action of a necessary being.