(Latin, esse, to be)
The basic or primary element in the being of a thing; the thing's nature, or that without which it could not be what it is. A thing cannot lose its essence without ceasing to exist, and the essential nature of a natural kind, such as water or gold, is that property without which there is no instance of the kind. Locke contrasted real essences, in something like this sense, with the nominal definition provided by a description of the common properties of a thing. Throughout Greek, scholastic, and some modern philosophy there have been many proposals of ways for finding the essences of things, and views about what science would be like if we did know them. The distinction between essential and accidental properties is rejected by holistic approaches to science, such as that advocated by Quine. See also essentialism, haecceity, quiddity.