Some argue meanings to be abstract logical objects but some philosophers, including Plato[citation needed], Augustine, Peter Abelard, Gottlob Frege, Ludwig Wittgenstein, J. L. Austin, John Searle, Jacques Derrida, and W.V. Quine, have offered alternative views. The nature of meaning, its definition, elements, and types, was discussed by Aristotle, Augustine, and Aquinas (also known as the AAA framework). According to them 'meaning is a relationship between two sorts of things: signs and the kinds of things they mean (intend, express or signify)'.[citation needed] One term in the relation of meaning necessarily causes something else to come to the mind in consequence. In other words: 'a sign is defined as an entity that indicates another entity to some agent for some purpose'. The types of meanings vary according to the types of the thing that is being represented.