  The second response would be to explain why spiritual substances are better posits than material ones. To this end, Berkeley emphasizes that we have a notion of spirit, which is just to say that we know what the word means. This purportedly contrasts with “matter,” which Berkeley thinks has no determinate content. Of course, the real question is: How does the term “spirit” come by any content, given that we have no idea of it?  In the Principles, Berkeley declares only that we know spirit through our own case and that the content we assign to “spirit” is derived from the content each of us assigns to “I” (PHK 139–140). In the Dialogues, however, Berkeley shows a better appreciation of the force of the problem that confronts him: