It has been suggested that a functionalist understanding of the metaphysics of psychological typing eliminates the prospect for psychological laws. Kim, Millikan, and Shapiro have each separately argued that, if psychological types as functional types are multiply realized, then the diversity of realizing mechanisms demonstrates that there can be no laws of psychology. Additionally, Millikan has argued that the role of functional attribution in the explanation of historical kinds limits the formulation of psychological principles to particular taxa; hence, psychological laws (...) applicable to any cognitive being are not possible. Both arguments against the possibility of psychological laws, I want to suggest, only succeed at showing that certain types of empirical principles will not be laws. I will suggest that a further type of empirical principle, grounded in the general constraints on the sustainability of population types, remains in the running as a candidate law. Importantly, the formulation of these principles presupposes a functionalist understanding of psychological typing. (shrink)