There are two texts that are crucial for Spinoza’s account of an “individual” (individuus), both of which focus on the case of bodily individuals. The first of these is a 1665 letter to the Secretary of the Royal Society, Henry Oldenburg, in which Spinoza responds to the request of his correspondent that he address “that difficult question concerning our knowledge of how each part of Nature agrees with its whole and in what way it agrees with other things” (Ep31). In response, Spinoza claims that since “all bodies are surrounded by others, and are determined by one another to existing and producing an effect in a fixed and determinate way, the same ratio of motion to rest [eadem rationem motus ad quietam] always being preserved in all of them at once,” it follows that “every body, insofar as it exists modified in a definite way, must be considered as a part of the whole universe, must agree with its whole and must cohere with the remaining bodies” (Ep32).