This epistemological ideal forms the core of Spinoza’s rationalistic ethics—and, hence, on one plausible account, the core of his Ethics. Spinoza’s monism entails that the sort of individuals that Aristotle regarded as primary substances are distinguished not by their own substantial unity, but by their conatus—their striving to persist. Thus, self-preservation is not just one possible goal of ethical agents; it is the very thing that makes those agents individuals. Our essence, and our ethical