Abstract

There is a general consensus among economists that the notion of rationality plays a central role in microeconomics. It is important to note, however, that they are far from agreement on the meaning of this notion. It would be difficult to lay out a set of welldefined concepts of rationality, but it might be useful to distinguish three quite different approaches around which economists tend to situate themselves when characterising this notion. I prefer to refer to three "approaches" rather than to three concepts, as I did in the title of the paper, because the concepts of rationality which correspond to these approaches cannot be isolated easily. Indeed, their unsettled definitions often overlap, and even when they purport to be related to opposing approaches, they are more or less interrelated. In any case, I propose to refer to these three approaches as "rationality-purposefulness", "rationality-efficiency", and "rationality-consistency". According to rationalitypurposefulness, an action is rational if and only if it is oriented towards the satisfaction of the agent's purpose, as most Austrian economists would tend to say. According to rationality-efficiency, an action is rational if and only if it actually maximises a positively valued magnitude such as utility or profit, as many neoclassical economists would say, especially when adopting a traditional approach. By contrast, rationality-consistency states that choices are rational if and only if it they are consistent as a set, which implies in particular that they are transitive.