 Suggestions for Further Reading: Aristotle, De Interpretatione, Ch. 9; Barnes and Cameron 2009; Boethius, The Consolation of Philosophy, Book V; Crisp 2007; Evans 1985; Lewis 1986; Markosian 1995; McCall 1994; Miller 2005; Richard 1981; Sullivan 2014; Taylor 1992; Torre 2011; Van Inwagen 1983.