In the first three sections of Berekeley's Principles of Human Knowledge, he argues:
No unintelligible things are possibleThe absolute existence of unthinking things is that which is unintelligibletherefore, No absolute existence of unthinking things is possible.
The argument is formerly valid. As a syllogism it is an EAE in mood and a figure 1 syllogism. So as far as validity is concerned it is good. What about the material content or truth value of the premises? Is it true that intelligibility is the limit for what is possible?
When Berekeley refers to the "absolute existence of unthinking things" he is referring to material objects that are extended in space, and lack any mental life; when he refers to "absolute existence" he is referring to an existence free from bening perceived by some mind. Berekeley thinks their existence is impossible because we can reduce all existence claims of unthinking external objects to the sense expereince of minds (spirits). He simply thinks that no sense can be made of a material substratum that exists without any qualities given by the mind, and that such a notion is contradictory. What does it mean, for instance, to say that there are extended things with no color? Any extended surface in our experience has color, in fact even extension is a concept which our minds develop by touch and sight, so what does it mean for an object to be extended, colored, hard (or soft), or any other quality without a reference to sensation of conscious minds? It doesn't seem to mean anything. In that case we can safely do away with the notion of absolute existence. So, maybe we can improve the clarity of the argument:
No contradictory things are possibleThe absolute existence of unthinking things is contradictorytherefore, the absolute existence of unthinking things is not possible.
Is Berekeley correct about his claims? We will see as we push on through the Principles of Human Knowledge. I will also draw on some of his other works where he covers much of the same ground.