Many of Locke's views were sharply criticized by rationalists and empiricists alike. In 1704 the rationalist Gottfried Leibniz wrote a response to Locke's work in the form of a chapter-by-chapter rebuttal, the Nouveaux essais sur l'entendement humain ("New Essays on Human Understanding"). Leibniz was critical of a number of Locke's views in the Essay , including his rejection of innate ideas, his skepticism about species classification, and the possibility that matter might think, among other things. Leibniz thought that Locke's commitment to ideas of reflection in the Essay ultimately made him incapable of escaping the nativist position or being consistent in his empiricist doctrines of the mind's passivity. The empiricist George Berkeley was equally critical of Locke's views in the Essay . Berkeley's most notable criticisms of Locke were first published in A Treatise Concerning the Principles of Human Knowledge . Berkeley held that Locke's conception of abstract ideas was incoherent and led to severe contradictions. He also argued that Locke's conception of material substance was unintelligible, a view which he also later advanced in the Three Dialogues Between Hylas and Philonous . At the same time, Locke's work provided crucial groundwork for future empiricists such as David Hume . John Wynne published An Abridgment of Mr. Locke's Essay concerning the Human Understanding , with Locke's approval, in 1696. Louisa Capper wrote An Abridgment of Locke's Essay concerning the Human Understanding , published in 1811.
These assumptions have been challenged by the discovery in 2009 of two small pieces of bone airing striations made by stone. One bone was from an antelope sized animal and the other from a bovid the size of a modern cow. The bones were found at Dikika, Ethiopia within the securely dated Sidi Hakoma formation and given an age of million years. By process of elimination, trampling of the bones underfoot by animals, toothmarks or their having been tumbled in a stream were ruled out and the only explanation for the markings appears to be the use of stone to scrape flesh from the bones and striking one of the bones to fracture it and extract the marrow.
In book III, Locke discusses abstract general ideas. Everything that exists in the world is a particular “thing.” General ideas occur when we group similar particular ideas and take away, or abstract, the differences until we are left only with the similarities. We then use these similarities to create a general term, such as “tree,” which is also a general idea. We form abstract general ideas for three reasons: it would be too hard to remember a different word for every particular thing that exists, having a different word for everything that exists would obstruct communication, and the goal of science is to generalize and categorize everything.