One of the most basic questions an ontology can address is: How many things, or substances, are there? A monist will say, ‘just one’. But there are different stripes of monism, and where the borders between these different views lie rests on the question, ‘To what does this “oneness” apply?’ Some monists apply ‘oneness’ to existence. Others apply ‘oneness’ to types. Determining whether a philosopher is a monist and deciphering what this is supposed to mean is no easy task, especially when it comes to those writing in the early modern period because many philosophers of the sixteenth, seventeenth, and eighteenth centuries include God in their ontologies. In The Principles, Anne Finch Conway offers an ontology that is often described as being both ‘vitalist’ and ‘monist’. I take this to mean that, for Conway, all that exists is in some way alive and that if asked ‘How many things, or substances, are there?’ Conway would say, ‘Just one’. But to what does this ‘oneness’ apply? And where does the point of disagreement between Conway and her interlocutors, Hobbes, Spinoza, More, and Descartes lie? In this paper, I argue that determining the answer to this first question turns out to be quite difficult. Nevertheless, we can still make sense of the second.