An epistemological term referring to beliefs that do not require previous experience. For example, the proposition "All bachelors are unmarried men" can be known to be true simply in virtue of the definition of 'bachelor'. All definitional beliefs, and hence all mathematical propositions, are known a priori. Rationalists (such as Descartes and Plato) maintain that each mind (or soul) contains a set of beliefs which is independent of sensory experience. These innate ideas are usually thought to serve as a kind of epistemic foundation for the rest of our knowledge (see 'Internalism' and 'Foundationalism'). Common examples of A priori beliefs and their role in cognition are our ability to make logical inferences about numbers, relations, causality, and other non-observable abstract entities.