Hegel himself was not immune to the refutatory quip. At the moment I am partway through the Postscript, and Kierkegaard has extremely sharp words against Hegel's system. Worse, however, are the witticisms done by certain analytic philosophers about the traditions preceding them. Lewis - and I cannot, unfortunately, find this quote - I remember making a terribly smarmy joke about "ridiculous" philosophies of Parmenides, Zeno, and some other Greeks, though he's the guy who invented modal realism. On to what Berkeley actually said now.

He's taking directly from the empirical tradition established by Locke. This much everyone knows. But it has to be kept in mind the influence from Malebranche and Bayle; who both contributed to the skeptical end of Berkeley's argument. I would like to get into detail but I don't have the time. The gist is that Malebranche's occasionalism needed only a severing from the essentially dead realm of extension, i.e. if our senses did not report causality between objects but only God puppeting those objects before us, then why (metaphysically) is there a need to posit those objects when we can skip to God causing our senses directly? Bayle attacks Malebranche for this and provides more skeptical ammunition. If I remember correctly though it is fully Berkeley's innovation to deny the abstract idea (in the sense he does). That denial was directly borrowed and used by Hume and in some sense is more important than the immaterialism. Similar thinking was behind Berkeley's refutation of unsound methods of proving derivation in calculus.

It's a shame that the manuscript for second part of this book remained unpublished from the poor reception of the first, and that it was later lost in Italy on one of Berkeley's travels. Poor initial reception of great works is the rule and not the exception. (I would go as far as to say: if a work is received well initially, and not from a slowly-established career but a spontaneity, then it is likely not a good one; it is well-accepted because it is what people want to hear, and all of its ideas must already be known.) Definitely worth reading this, he is a part of the canon. Read Locke first of course. I haven't read the Three Dialogues but don't let the "Treatise" part of the title trick you, it's a relatively short work and not that dense.