Nietzsche offers us an account of how different drives interact with one another; it is rich but also appears to risk the homunculus fallacy. Competing attempts to deflect this charge on his behalf share an implicit consensus about the ‘epistemic ends’ of the account: they assume Nietzsche is trying to provide true explanations of psychological phenomena. I argue against this consensus. I claim that Nietzsche's characterisations of drive interaction are to be taken as fictive and are not intended to have (...) explanatory value. They nevertheless facilitate genuine epistemic achievement. Drawing on Catherine Elgin's account of the epistemic role of idealised models in science, I argue that Nietzsche's account of drive interaction is a ‘model of the mind’ that, despite relying on falsehoods, can exemplify features of our psychology that aid us in making novel predictions. We then see that Nietzsche neatly sidesteps the homunculus fallacy; we can further understand more fully what Nietzsche hopes his drive psychology will teach us. We can now resolve, for example, outstanding interpretative puzzles about the relationship between psychic integration and Nietzsche’s distinctive notion of spiritual health. (shrink)