According to Berkeley, matter and extension (the main property of matter that was supposed to be its occupation of space) were abstract, general ideas, which is to say that the words naming or describing them did not refer to real ideas. Since only ideas, minds, and God exist, matter and extension did not exist for Berkeley—there was nothing real corresponding to them. Berkeley applied the same criticism to our presumptive ideas of causation and the distinction between primary and secondary qualities. He looked for the ideas of sense or imagination to back them up, and found none.

In the case of causation, Berkeley was basically an occasionalist.