In Ontology (a subdiscipline of Metaphysics) Materialism is the view which holds that there is but one kind of properly basic stuff - matter - from which everything in the Universe is composed.

In the Philosophy of Mind there are at least four distinct materialist positions all of which hold that mental events like thoughts are material (or brain) phenomena:

What each of these views shares in common is a rejection to the belief that the 'mind' or 'soul' is a metaphysical entity distinct from the body.