Time, Thought, and Vulnerability presents the results of an investigation of the conditions on which circumstanced which lie beyond the ken (let alone the control) of a reasoner may jeopardize the validity of inferences whose correctness is supposed to be evaluable on a purely a priori basis. The discussion involves a careful examination of the ongoing debate about the transparency of mental content and the accessibility of the logical form of inferences. A comparison with the debate about the vicissitudes of preservative memory in a temporalist semantics is articulated through a comparison of the arguments presented by Mark Richard and Paul Boghossian against, respectively, temporalism and anti-individualism. Finally, the inquiry is dissociated from those two theoretical frameworks (temporalism versus eternalism; individualism versus anti-individualism) in favor of a direct discussion of the postulate of transparency of logical form.