1 Van Inwagen refers to Black, Max, “The Elusiveness of Sets,” Review of Metaphysics, 24 (1971): 614–36, and Morton, Adam, “Complex Individuals and Multigrade Relations,” Nous, 9 (1975): 309–18. I urge the significance also of Boolos, George, “To Be Is to Be the Value of a Variable (Or to Be Some Values of Some Variables),” Journal of Philosophy, 81 (1984): 430–49.
2 Halmos, Paul, Naïve Set Theory (London and New York: Van Nostrand, 1960).
3 Nihilism in van Inwagen's sense is the denial of the existence of composite objects other than living organisms. Peter Unger calls himself a Nihilist because he denies the existence of shirts and trousers and shoes—and indeed of any of the things referred to by count nouns in a natural language—but that is not quite the same thing as a denial of the existence of all composite objects. Unger allows that there may be composite objects for which we have no names. Van Inwagen denies this. See Unger, Peter, “There Are No Ordinary Things,” Synthese, 41 (1979): 117– 4, and 'Scepticism and Nihilism,” Nous, 14 (1980): 517–45.
Universalism is championed by Lewis, David, for instance, in On the Plurality of Worlds (Oxford: Basil Blackwell, 1986). The most influential exponent is probably Quine, W. V. O. in Word and Object (Cambridge, MA: Harvard University Press, 1960); but the foundations were laid mainly by Goodman, Nelson, The Structure of Appearance (Cambridge, MA: Harvard University Press, 1966).
4 I first heard Lewis's refutation of van Inwagen during iscussion after a paper presented by van Inwagen in Princeton in 1983. Related arguments appear in Lewis, David, On the Plurality of Worlds (Oxford: Basil Blackwell, 1986), pp. 212–13.