An Essay Concerning Human Understanding is one of
John Locke's two most famous works, the other being his
Second Treatise on Civil Government. First appearing in
1690, the essay concerns the foundation of human knowledge and understanding. He describes the mind at birth as a blank slate (
tabula rasa, although he did not use those actual words) filled later through
experience. The essay was one of the principal sources of
empiricism in modern philosophy, and influenced many enlightenment
philosophers, such as
David Hume and
Bishop Berkeley.
Book II of the Essay sets out Locke's theory of ideas, including his distinction between passively acquired simple ideas, such as "red," "sweet," "round," etc., and actively built complex ideas, such as numbers, causes and effects, abstract ideas, ideas of substances, identity, and diversity. Locke also distinguishes between the truly existing primary qualities of bodies, like shape, motion and the arrangement of minute particles, and the secondary qualities that are "powers to produce various sensations in us" such as "red" and "sweet." These secondary qualities, Locke claims, are dependent on the primary qualities. He also offers a theory of personal identity, offering a largely psychological criterion. Book III is concerned with language, and Book IV with knowledge, including intuition, mathematics, moral philosophy, natural philosophy ("science"), faith, and opinion.
Locke's main thesis is that the mind of a newborn is a blank slate (tabula rasa) and that all ideas are developed from experience. Book I of the Essay is devoted to an attack on nativism or the doctrine of innate ideas. Locke allowed that some ideas are in the mind from an early age, but argued that such ideas are furnished by the senses starting in the womb for instance, differences between colors or tastes. If we have a universal understanding of a concept like sweetness, it is not because this is an innate idea, but because we are all exposed to sweet tastes at an early age.
Along these lines, Locke also argued that people have no innate principles. Locke contended that innate principles would rely upon innate ideas, which do not exist. For instance, we cannot have an innate sense that God should be worshipped, when we cannot even agree on a conception of God or whether God exists at all. One of Locke's fundamental arguments against innate ideas is the very fact that there is no truth to which all people attest. He took the time to argue against a number of propositions that rationalists offer as universally accepted truth, for instance the principle of identity, pointing out that at the very least children and idiots are often unaware of these propositions.
