Hypokeimenon (Greek: ὑποκείμενον), later oftenmaterial substratum, is a term inmetaphysics which literally means the "underlying thing" (Latin:subiectum).
To search for thehypokeimenon is to search for thatsubstance that persists in a thing going through change—its basicessence.
Aristotle defined ahypokeimenon in narrowly and purely grammatical terms, as something which cannot be apredicate of other things, but which can carry other things as its predicates.[1]
The existence of a material substratum was posited byJohn Locke, with conceptual similarities toBaruch Spinoza'ssubstance andImmanuel Kant's concept of thenoumenon (inThe Critique of Pure Reason).
Locke theorised that when allsensible properties were abstracted away from an object, such as its colour, weight, density or taste, there would still be something left to which the properties had adhered—something which allowed the object to exist independently of thesensible properties that it manifested in the beholder. Locke saw thisontological ingredient as necessary if one is to be able to consider objects as existing independently of one's own mind. The material substratum proved a difficult idea for Locke as by its very nature its existence could not be directly proven in the manner endorsed by empiricists (i.e., proof by exhibition in experience).[2] Nevertheless, he believed that the philosophical reasons for it were strong enough for its existence to be considered proven.
The existence of the substratum was denied byBerkeley. In hisThree Dialogues Between Hylas and Philonous, Berkeley maintained that an object consists of nothing more than thosesensible properties (or possiblesensible properties) that the object manifests, and that thosesensible properties only exist so long as the act of perceiving them does.[3]: l