Reasons, rationality, and motivation

According to one of the most influential and popular theories in the contemporary theory of action, an agent S is motivated to perform a certain act A if and only if she endorses some set of reasons R on the basis of which it follows that she should perform A, and given that she does not suffer from some sort of practical irrationality (e.g. depression, weakness of will, psychopathy, mental or physical exhaustion etc.). At least at first glance, this theory - which is known as the rationalist motivational internalism - appears to be uncontroversial and unproblematic. Yet, over the past ten years, this popular position has faced numerous very serious objections. In the course of this work, I intend to present some of these objections, in order to justify the claim that the concept of practical irrationality - i.e. the concept that plays the central role in this particular version of internalism - should be left out from the philosophical explanation of motivation. I will then attempt to defend the conclusion that the rationalist motivational internalism represents a completely inadequate theory of motivation.