The challenge of "Keynes vs. Classics" has been considered by economists and historians of economic thought. The centre of this challenge is: whether Keynes has really presented a new theory. In fact, the historical question is: whether the Keynesian Revolution has occurred? If we accept the Scientific Revolution concept as transforming a new paradigm in economic explanations and predictions, then, we can argue that there are three main differences between Keynes and the Classics. These differences, considered as the elements of Keynesian Revolution, are philosophic-epistemic, methodological and theoretical differences. The revolution, in terms of the nature of economics is considered to be a philosophic-epistemic difference. According to this aspect, Keynes transformed the nature of economics, as considered by classical economists. From the viewpoint of methodological difference, Keynes has used the equilibrium method for economic analysis. Furthermore, the most important theoretical elements are found in many categories such as investment, saving, interest rate, policymaking, rigidity of prices and wages, non-clearing of markets and uncertainty. The final conclusion is that the Keynesian Revolution has occurred in all these aspects.
JEL Classifications: E20، B12، B22، B31، B41