This paper offers a precise definition of neoclassical economics based on three axioms which lie at the latter's foundations. This definition is all inclusive in that it applies as much to the neoclassical economic models of the late 19th century as it does to today's more flexible and 'inclusive' models. The paper argues that these axioms, simultaneously, (a) provide the foundation for neoclassicism’s discursive success within the social sciences and (b) are the deep cause of its theoretical failure. Moreover, (a) and (b) reinforce one another as neoclassicism's discursive power (which is largely due to the hidden nature of its three foundational axioms) makes it even less likely that it will conduct an open, pluralist debate on its theoretical foundations (i.e. the three axioms which underpin it).