Forthcoming in Theoria Frege on Anti-Psychologism and the Role of Logic in Thinking * Thomas Lockhart † Auburn University abstract According to (what I call) the Explanatory Problem with Frege’s Platonism about Thoughts, the sharp separation between the psychological and the logical on which Frege famously insists is too sharp, leaving Frege no resources to show how it could be legitimate to invoke logical laws in an explanation of our ac- tivities of thinking. I argue that there is room in Frege’s philosophy for such justificatory explanations. To see how, we need first to correctly understand the lesson of Frege’s attack on psychologism as fundamentally marking a contrast between justification and explanation, and, second, we must take Frege to be committed to the idea that the laws of truth are normatively constitutive for the process of thinking. 1 Introduction Frege articulates three principles at the opening of the Foundations of Arithmetic. According to the first, we must always “separate sharply the psychological from the logical, the subjec- tive from the objective” (Frege 1980, p. X). This encapsulates the lesson of Frege’s attack on psychologism. The fundamental mistake of the psychological logician, as Frege diagnoses him, is to conflate the psychological with the logical, the subjective with the objective. The importance of a separation of this kind appears uncontroversial. There is little temptation, for example, to confuse psychological generalizations about how we tend to think and reason with claims about how we ought to think and reason. * Two anonymous referees for Theoria provided extremely helpful comments on an earlier draft of this paper. I’d also like to thank audiences at the Auburn University Philosophy Society, the Alabama Philosophical Society, the Joint Session of the Aristotelian Society and the Mind Association, and the University of Mississippi. Finally, I am greatly indebted to Jennifer Lockhart for a great deal of help with this material. † lockhartt@auburn.edu 1