Accumulating evidence suggests that not only diseases of old age, but also normal aging, affect elderly adults’ ability to draw on the framework theories that structure our abstract causal-explanatory knowledge, knowledge that we use to make sense of the world. One such framework theory, the cross-culturally universal vitalist biology, gives meaning to the abstract concepts life and death. Previous work shows that many elderly adults are animists, claiming that active, moving entities such as the sun and the wind are alive (Zaitchik & Solomon, 2008). Such responses are characteristic of young children, who, lacking an intuitive theory of biology, distinguish animals from non-animals on the basis of a theory of causal and intentional agency. What explains such childlike responses? Do the elderly undergo semantic degradation of their intuitive biological theory? Or do they merely have difficulty deploying their theory of biology in the face of interference from the developmentally prior agency theory? Here we develop an analytic strategy to answer this question. Using a battery of vitalist biology tasks, this study demonstrates—for the first time—that animism in the elderly is due to difficulty in deployment of the vitalist theory, not its degradation. We additionally establish some powerful downstream consequences of theory deployment difficulties, demonstrating that the elderly’s use of the agency theory is not restricted to animist judgments—rather, it pervades their explicit reasoning about animates and inanimates. Extending the investigation, we identify specific cognitive mechanisms implicated in adult animism, finding that differences between young and elderly adults are mediated and moderated by differences in inhibition and shifting mechanisms. The analytic strategy developed here could help adjudicate between degradation and deployment in other conceptual domains and other populations.