Whether scientific approaches can be "integrated" depends on the meaning of the word. Different ontological claims about causal mechanisms may prevent some theoretical integrations, yet the capacity of one theoretical system to explain phenomena identified by another may enable empirical integration. Baumert and colleagues valuably suggest that phenomena identified by personality's trait-theoretic approaches can be understood through bottom-up explanatory strategies that reference interactions among underlying social-cognitive mechanisms (cf. Cervone, 1999). This commentary highlights the role of enduring knowledge structures in formulating explanations of personality variability and consistency. Copyright (C) 2017 European Association of Personality Psychology