Essentialism

The tendency has always been strong to believe that whatever received a name must be an entity or being, having an independent existence of its own, and if no real entity answering to the name could be found, men did not for that reason suppose that none existed, but imagined that it was something particularly abstruse and mysterious. Essentialism is a concept in philosophy and psychology concerning the underlying "true" metaphysical nature of objects and/or subjects. As a philosophy, essentialism is often the belief that an object has a set of necessary properties that make it said object. This is to say the object possesses a "defining" set of properties that it must have rather than could have in order to be said object. Properties an object may or may not possess are often referred to as "accidental properties". For example it could be considered part of a bird's essence that it is an animal, but it's merely accidental if a bird can fly.

Essentialism not only is applied to the idea of objects having necessary, sufficient, and defining properties, but abstract concepts as well. Sometimes a traditional analysis of abstract concepts like "justice" or "knowledge" is treated as an essentialism of certain kind — often objected to when counter-examples to said analysis is found.

Aristotelian essentialism
Aristotelian essentialism was defined by W. V. O. Quine, writing in 1966, as "the doctrine that some of the attributes of a thing (quite independently of the language in which the thing is referred to, if at all) may be essential to the thing and others accidental. E.g. a man, or talking animal, or featherless biped (for they are all the same things), is essentially rational and accidentally two-legged and talkative not merely qua man, but qua itself."

Although Quine never confirms that Aristotelian essentialism was indeed Aristotle's doctrine, or if it is ever mentioned in his writing, or commentary on his writings, he states that according to Aristotle, objects, whether singular or under some general description, have "essences". These "essences" are those properties of the objects without which the object ceases to be what it is. In other words, removing, or altering, these properties would literally destroy the object.

For example, the doctrine holds that humans are essentially rational — meaning they have the faculty of reason — but it's only by chance that they are two-legged. In order to convince yourself of this, imagine a human with only one leg. Is that still a human? Our reason tells us that this person is human, even with one leg. However, if you were to picture a human without reason, could you then imagine that person as human? You would most likely see them as a beast, or more cruelly, a vegetable, thus destroying their "humanness." Therefore, reason is essential to being human.

It follows that "essence" can be described as follows:

The essence, E, of an object, o, is a property (or set of properties, which can be treated as a property) such that we cannot conceive of o as lacking E. In case O is a general term, we say that any instance of O, call it o, without E is not an O.

Scientific essentialism
Scientific essentialism refers to the existence of posited "natural kinds" that can be found within the natural world. Common examples that are given are any of the chemical elements. Scientific essentialism has fallen out of favor in contemporary philosophy of science, though it found defenders in Saul Kripke and Hilary Putnam, who defended a more semantic (as opposed to metaphysical) type of essentialism.

Biological essentialism
Biological essentialism is the application of Aristotelian essentialism to biology, positing a fixity of species. Essentialism is a discredited view within biology. Evolutionary biologist Ernst Mayr popularized the argument that Charles Darwin's formulation of evolution was what ultimately discredited essentialism by introducing population thinking. However, this claim has come under criticism from revisionists who argue that essentialism arose as a reaction to Darwin.

Psychological essentialism
Psychological essentialism refers to the tendency of people to group objects or people by some "natural" underlying "essence" that they are thought to share. Psychological essentialism opposes Jean Piaget's view of children as "concrete" thinkers who group objects based on superficial characteristics. Essentialist categorizations of organisms (including people, e.g., by race) are considered to be part of a "folk taxonomy" or "folk biology." While essentialism is a mechanism associated with folk biology, it does not necessarily have to be applied to "natural kinds." When essentialist beliefs are held with respect to social groups, they are associated with endorsement of stereotypes and discrimination.