|Criticism=In some quarters, Locke’s ''An Essay Concerning Human Understanding'' was heavily criticized. Gottfried Wilhelm Leibniz (1646-1716) responded, point-by-point, to Locke’s work in a book length rebuttal, ''New Essays on Human Understanding'', which he finished in 1704, but wasn't published until sixty years later. [[CiteRef::Look (2017)]] Leibniz rejected Locke's claim that the senses were the ultimate source of all our ideas. He wrote that "Experience is necessary...if the soul...is to take heed of the ideas that are within us. But how could experience and the senses provide the ideas? Does the soul have windows? Is it similar to writing tablets or wax? Clearly, those who take this view of the soul are treating it as fundamentally corporeal", a possibility that Locke was willing to countenance, but Leibniz found abhorrent. [[CiteRef::Look (2017)|p. 40]]
Rejecting Leibniz rejected Locke's claim that all knowledge derives from experiencethe mind began like a blank sheet of paper, because this would make new minds separate but identical, he a possibility ruled out by his Principle of the Identity of Indiscernibles.[[CiteRef::Look (2017)]] He allowed only that contingent truths might be learned through with the senses. The knowledge of logically necessary general principles could not. This includes necessary truths of pure mathematics, logic, and some areas of metaphysics and ethics. These cannot come from the senses because no number of specific instances of experiencing them experiences could demonstrate their necessity. [[CiteRef::Look (2017)]] Therefore, "the proof of them can only come from inner principles, which are described as innate".[[CiteRef::Leibniz(1705a)|p. 3]] Thus, he rejected Locke's claim that there were no innate ideas. To explain why everyone doesn't have access to these innate ideas, he wrote that "It would indeed be wrong to think that we can easily read these eternal laws of reason in the soul. . .without effort or inquiry; but it is enough that they can be discovered inside us if we give them our attention: the senses provide the prompt, and the results of experiments also serve to corroborate reason, rather as checking procedures in arithmetic help us to avoid errors of calculation in long chains of reasoning" . [[CiteRef::Leibniz(1705a)|p. 3]]Leibniz's criticisms of Locke touched off a prolonged debate between empiricists, who maintained, with Locke, that all knowledge derives from experience, and rationalists like Leibniz, who maintained that some knowledge is derived by means other than experience, and must therefore be innate. [[CiteRef::Markie (2017)]] George Berkeley (1685-1753)