Definition a priori: An a priori argument is one where certain basic principles are assumed to be true. Therefore, it is not necessary to use empirical evidence but rely on the axioms being true.
A priori contrasts with A posteriori – which is arguments based on evidence and facts.
An example of a priori in economics
A firm will produce where MR=MC because we assume that firms are profit maximisers.
However, this a priori argument of assuming profit maximisation may not be true in the real world. There are many other examples of business objectives such as sales maximisation or profit satisficing.
A big a priori assumption in economics is that consumers are rational. Classical economics has faced difficulties when these assumptions do not always occur. For example, in the real world, we see examples of irrational behaviour.
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Published 28 Oct 2012, Tejvan Pettinger. www.economicshelp.org