In this paper I investigate whether there are genuine and irreducible pressures of diachronic rationality grounded on the structure of the subject rather than on substantive considerations, such as pragmatic ones. I argue that structural pressures of diachronic rationality have a limited scope. The most important pressure only tells against arbitrary interference with the mechanisms for the retention of attitudes over time. I then argue that in the practical case, a substantial account in terms of the agent's temporal identity appears (...) more promising than a purely structural one, but in the end it still leaves many questions about diachronic practical rationality underdetermined. (shrink)