This chapter explores important parallels between Socrates’ response to Anaxagoras’ materialist account of mind in Plato’s Phaedo, and Raymond Tallis’ criticisms of scientistic or purely materialistic accounts of mind. Both Socrates and Tallis share the view that knowledge is central to and definitive of human being, and their defenses of this view can be regarded more generally as defenses of the principle of sufficient reason as it applies both to human being and to mind or consciousness itself. After outlining Socrates’ response to Anaxagoras, I show how some of Tallis’ central criticisms of naturalistic accounts of mind echo and develop Socrates’ views. I conclude with a comparison between the optimism which Socrates expresses both in the Phaedo and at the conclusion of his trial in the Apology, and the philosophical hope for which Tallis argues in much of his writing.