Critically assess Locke’s account of abstraction.

Please make sure you include empiricism, what is an idea, Locke’s account of abstract ideas and other areas that Locke covered when writing this essay.
Some books and links:
1) John Locke, An Essay Concerning Human Understanding
2) George Berkeley, The Principles of Human Knowledge
3) Monroe Beardsley, ‘Berkeley on Abstract Ideas’ in Locke and Berkeley, ed. by Martin and Armstrong (London: Macmillan, 1968
4) http://plato.stanford.edu/entries/locke/
5)The Cambridge Companion to Locke’s ‘Essay Concerning Human Understanding