Substance theory

Essence () has various meanings and uses for different thinkers and in different contexts. It is used in philosophy and theology as a designation for the property or set of properties or attributes that make an entity the entity it is or, expressed negatively, without which it would lose its identity. Essence is contrasted with accident, which is a property or attribute the entity has accidentally or contingently, but upon which its identity does not depend.

basic ontological concept

Essentialism is the view that objects have a set of attributes that are necessary to their identity. In early Western thought, Platonic idealism held that all things have such an "essence"—an "idea" or "form". In Categories, Aristotle similarly proposed that all objects have a substance that, as George Lakoff put it, "make the thing what it is, and without which it would be not that kind of thing". The contrary view—non-essentialism—denies the need to posit such an "essence". Essentialism has been controversial from its beginning. In the Parmenides dialogue, Plato depicts Socrates questioning

philosophical question of whether properties exist, and if so, what they are

in metaphysics, repeatable or recurrent qualities that can be instantiated or exemplified by many particular things

Hylomorphism is a philosophical doctrine developed by the Ancient Greek philosopher Aristotle, which conceives every physical entity or being (ousia) as a compound of matter (potency) and substantial form (act), with the generic form as immanently real within the individual. The word is a 19th-century term formed from the Greek words ὕλη (hyle: "wood, matter") and μορφή (morphē: "form"). Hylomorphic theories of physical entities have been undergoing a revival in contemporary philosophy.

Haecceity (; from the Latin , 'thisness') is a term from medieval scholastic philosophy, coined by followers of Duns Scotus to denote a concept that he seems to have originated: the irreducible determination of a thing that makes it this particular thing. Haecceity is a person's or object's thisness, the individualising difference between the concept "a person" and the concept "Socrates" (i.e., a specific person). In modern philosophy of physics, it is sometimes referred to as primitive thisness.

Hypokeimenon (Greek: ὑποκείμενον), later often material substratum, is a term in metaphysics which literally means the "underlying thing" (Latin: subiectum).