The idea that our recognition of others’ mental states is beset, not only by contingent but constitutional uncertainty is one to which Wittgenstein returns throughout his later work. And yet it remains an underexplored component of that work. The primary aim of this paper is to better understand what Wittgenstein means when he describes the mental as constitutively uncertain, and his conception of the kind of knowledge of others' mental lives consistent with it. The secondary aim is to connect Wittgenstein’s (...) discussion of the constitutive uncertainty of the mental with two further components of his later thought—specifically, his remarks on aspect perception and on the pattern-like nature of the emotions. (shrink)