Is there any inconsistency in Berkeley's philosophy?

Question

Does Berkeley's empiricist philosophy contain any inconsistencies? What are the inconsistent sides of Locke's or Hume's philosophies? How is Berkeley's world different from a Matrix-like world?

The questions are motivated by the following exchange between Sophie and Alberto about Berkeley in Gaarder's philosophical novel Sophie's World:

“He felt that current philosophies and science were a threat to the Christian way of life, that the all-pervading materialism, not least, represented a threat to the Christian faith in God as creator and preserver of all nature.”
“He did?”
“And yet Berkeley was the most consistent of the empiricists.”
“He believed we cannot know any more of the world than we can perceive through the senses?”
“More than that. Berkeley claimed that worldly things are indeed as we perceive them, but they are not ‘things.’ “
“You’ll have to explain that.”
“You remember that Locke pointed out that we cannot make statements about the ‘secondary qualities’ of things. We cannot say an apple is green and sour. We can only say we perceive it as being so. But Locke also said that the ‘primary qualities’ like density, gravity, and weight really do belong to the external reality around us. External reality has, in fact, a material substance.”
...
“This is just what Berkeley questioned, and he did so by the logic of empiricism. He said the only things that exist are those we perceive. But we do not perceive ‘material’ or ‘matter.’ We do not perceive things as tangible objects. To assume that what we perceive has its own underlying ‘substance’ is jumping to conclusions. We have absolutely no experience on which to base such a claim.”

Answer 1

A major problem Berkeley would face today was actually solved in his time with what I would actually consider one of the most elegant solution to a philosophical argument ever proposed. In a famous incident, Ronald Knox raised a major criticism to Berkley with a limerick:

There once was a man who said "God
Must think it exceedingly odd
If he finds that this tree
Continues to be
When there's no one about in the Quad."

An unknown individual solved this problem with another limerick:

Dear Sir, Your astonishment's odd.
I am always about in the Quad.
And that's why the tree
Will continue to be
Since observed by Yours faithfully, God

Although this argument is an amazingly simple solution that completely and unambiguously solves the problem (something that almost never happens in philosophy), it relies on the axiom that an omniscient being exists. In the centuries since this argument have been published, such an assumption has fallen out of fashion.

On the other hand, I can think of a possible solution Berkeley could propose that would also solve the problem. Unfortunately, it relies on quantum field theory and faces problem from special relativity. Considering how both of these things have been horrible misused in amateur philosophers like me in the past, I am going to save myself a lot of embarrassment by not posting it unless someone asks me to.

Answer 2

"Inconsistency" is too assertive a word for philosophy. Let me draw an analogy between philosophy and chess. In master-level chess, there are strong and weak moves, rarely, there are right or wrong moves (mostly, they occur in cramped positions with very few choices). Likewise in philosophy, there are strong or weak arguments, incipient or mature views, but statements that can be plainly said to be true or false occur rarely and so do inconsistencies. Philosophical theories are too large to be tested; the main force of philosophical advancement is enrichment and sharpening of concepts, while introducing novel ones; not replacing one theory with another. In this respect, philosophy is closer to mathematics than science. So, we had better reserve the term "inconsistency" for formal contexts.

It is a good practice to stay away from formulaic definitions of mainstream views like empiricism, rationalism, etc. and try to view them as methodological frameworks in which a dominant thread runs throughout, shaping various questions and answers

To have a glimpse of the relevance of Berkeley's views to today's concerns, I'd advise you to read Popper's paper A Note on Berkeley as Precursor of Mach (1953, The British Journal for the Philosophy of Science 4, pp. 26-36).

Answer 3

I'm currently reading W. T. Jones A History of Western Philosophy series, and I find his comment on Berkeley might answer your question:

The trouble is that Berkeley had inherited the Cartesian and Lockian assumption that minds know bodies by means of ideas. He was quite critical about the "body" part of this assumption, for it offended his religious sensibilities. And when he saw that, in this view, bodies are unknowable, he was only too glad to drop them. But he was quite uncritical about the rest of the formula; it did not occur to him to ask himself whether the rest of the scheme might not be invalidated by the same line of argument. His position was that "of course" there are minds and "of course" each mind knows its own ideas. Hence, if there are no bodies for minds to know, reality naturally consists in minds and their ideas.

Dr. Samuel Johnson once undertook to refute Berkeley by kicking a stone. Although Berkeley had a perfectly good reply to this criticism as Johnson stated it, one can sympathize with the critic. What one kicks is not ideas, but stones. Why call the stone that I kick "my idea of a stone"? The truth is that "idea of" is as empty of meaning as "material substance"—a verbal complication that confuses, rather than assists, our efforts to think straight. Philonous is really not much better off than poor Hylas, who tried to defend his material substratum by arguing that if we admit properties, we must allow substances for them to inhere in. Similarly, Berkeley might say, "Nobody denies that there are minds, and what minds know is ideas." But, unfortunately, this is only a matter of definition. Of course minds know only ideas, if one defines the objects of knowledge as ideas! At times Berkeley seemed to see that calling the empirical data "ideas" was just a manner of speaking, and in more than one place he insisted that he had left the physical world just what it was before the theory was put forward.

Unfortunately, the term "idea" carried as many special connotations of its own as had the objectionable "material substance." Berkeley pointed out a very important truth in insisting that a stone is just a set of coexisting data, not a material substratum with properties. But it was misleading to add that these data were private mental states.