Panpsychism is the view that mentality is pervasive: each thing exhibits psychological features. On some versions of panpsychism, each thing has perceptions; on other versions, each thing has experiences or is conscious. In seeing mentality as extending much more broadly than we might ordinarily think, the panpsychist needs to provide a powerful argument for this position, and throughout the history of philosophy up to the present day, certain philosophers – no doubt, a minority – have tried to do precisely that. Among Spinoza’s rough contemporaries, Cavendish, Conway, and Leibniz among others belong to this minority. Spinoza is often regarded – though, as we will see, not without controversy – as falling into this category too, and the arguments for panpsychism that have been attributed to him are continuous with some of the most important arguments that philosophers nowadays employ to support panpsychist views.