 At least until recently, the standard metaphysical understanding of the meaning of “atheism” was so ingrained in philosophy that philosophers could safely use the word “atheism” in that sense without worrying that they might be misunderstood and without feeling any need to defend it. For example, in his book, Arguing About Gods, Graham Oppy (another atheist) repeatedly treats “agnostic” (in the psychological sense of someone who suspends judgment about God’s existence) and “atheist” as mutually exclusive categories (2006, 1, 15, and 34) without offering any justification for doing so. The only plausible explanation for his failure to provide justification is that he expects his readers to construe the term “atheism” in its metaphysical sense and thus to exclude from the class of atheists anyone who suspends judgment about whether gods exist.  Another sign of how dominant the standard definition is within the field of philosophy is the frequent use of the term “non-theist” to refer to the broader class of people who lack the belief that God exists.