The doctrine that it is correct to distinguish between those properties of a thing, or kind of thing, that are essential to it, and those that are merely accidental. Essential properties are ones that it cannot lose without ceasing to exist. Thus a person wearing a hat may take off the hat, or might not have been wearing the hat, but the same person cannot cease to occupy space, and we cannot postulate a possible situation in which the person is not occupying space. If we agree with this (it is not beyond debate, which illustrates the difficulty with essentialism), occupying space is an essential property of persons, but wearing a hat an accidental one. The main problem is to locate the grounds for this intuitive distinction. One suggestion is that it arises simply from the ways of describing things, and is therefore linguistic or even conventional in origin. Contrasted with this (the nominal essence) is the Lockean idea that things themselves have underlying natures (real essences) that underlie and explain their other properties. 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.

Essentialism is used in feminist writing of the view that females (or males) have an essential nature (e.g. nurturing and caring versus being aggressive and selfish), as opposed to differing by a variety of accidental or contingent features brought about by social forces. See also determinism, biological; neurosexism.