What is the nature of the evidence provided by thought experiments in philosophy? For instance, what evidence is provided by the Gettier thought experiment against the JTB theory of knowledge? According to one view, it provides as evidence only a certain psychological proposition, e.g. that it seems to one that the subject in the Gettier case lacks knowledge. On an alternative, nonpsychological view, the Gettier thought experiment provides as evidence the nonpsychological proposition that the subject in the Gettier case lacks (...) knowledge (e.g., Williamson 2007). Given the centrality of thought experiments to philosophical enquiry, the correct account of thought experiment evidence is important for understanding the nature of philosophical methodology. Further, Williamson argues that a misguided adherence to the psychological view of thought experiment evidence encourages scepticism about philosophy since it opens a gap between our evidence and the nonpsychological subject matter of philosophy. The main aim of this paper is to defend the psychological view against recent objections. In particular, I argue that even if thought experiment evidence is psychological, it can still provide justification for non-psychological claims which are the subject matter of philosophy. (shrink)