In this paper, I clarify some central aspects of Stoic thought concerning identity, identification, and so-called peculiar qualities (qualities which were seemingly meant to ground an individual’s identity and enable identification). I offer a precise account of Stoic theses concerning the identity and discernibility of individuals and carefully examine the evidence concerning the function and nature of peculiar qualities. I argue that the leading proposal concerning the nature of peculiar qualities, put forward by Eric Lewis, faces a number of objections, (...) and offer two constructive suggestions which turn upon reconsidering the nature and function(s) of peculiar qualities. Finally, I examine a simple but potent Academic argument against the view that identification requires detecting some attribute(s) unique to the relevant individual. Such an argument is, I argue, largely successful and may have encouraged later Stoics not to think that peculiar qualities enable identification. (shrink)