Love it or hate it, no contemporary student of philosophy can ignore John Locke's Essay Concerning Human Understanding. Initially published in December of 1689, it has been one of the most influential books of the last three centuries; in fact, it is not much of a stretch to say that every subsequent philosopher has been touched by Locke's ideas in some way. The unique importance of Locke's Essay lies in the fact that it is the first systematic presentation of an *empiricist* philosophy of mind and cognition: a theory of knowledge and belief based wholly on the principle that everything in our mind gets there by way of experience. The first principle of an empiricist philosophy of mind is often illustrated by the notion of a Tabula Rasa, or a blank slate (an illustration Locke himself made famous in the Essay): at birth, our minds arrive into this world completely empty, like a pure white sheet of paper, and it is only as experience "writes" on this paper that ideas and thoughts begin to form.
As the first explicit formulation of an empiricist philosophy, the Essay had a profound effect upon the intellectual climate of the late 17th century, which until then was wholly dominated by two warring camps, the established Aristotelian *Scholastics* on the one hand and the upstart Cartesian *rationalists* on the other. Locke, with his thoroughgoing, but rational, empiricism, cut a middle road through these two extreme positions, and offered an alternative view of the world and our access to it, which proved enticing to many thinkers. Roughly contemporary empiricists such as George Berkeley, and slightly later ones such David Hume, built their philosophies on the foundation Locke had laid out. Kant, seeking to reconcile empiricism with rationalism in the late 18th century, drew heavily from Locke's work, in large part giving precise and novel formulation to ideas which stemmed originally from the Essay. Even in the 20th century, empiricists such as Rudolph Carnap, G.E. Moore, and W.V. Quine, explicitly expressed their debt to Locke's writings. Locke's contribution to empiricism can hardly be overstated; not only did he give us one of the most detailed and plausible accounts of the position to date, but, in a sense, he spurred the entire movement with his innovative ideas.
The Essay, though, is far from a narrow work on a single topic. It is, in fact, staggeringly wide-ranging, covering such diverse topics as philosophy of language, philosophy of logic, moral philosophy, and philosophy of religion in addition to the better known philosophy of mind and cognition. Locke treats each of these topics intelligibly and provocatively, making his book a convenient starting point for students and scholars alike.