Berkeley said that the only "things" out there are:
1. minds- (the only existing things) a thing that has ideas
2. ideas- can be imprinted on the senses as a result of passions/ mental operations or products of memory/ imagination. He said that a number of separate ideas can be collected under one name. And ideas can only exist in the mind.
What about objects? Berkeley said that our only connection to objects is through our ideas. Locke ...
Outline of Berkeley's theory of ideas and argument for G-d's existence.