Do you have reasons for your reasons? An attempt to make nihilism an attractive alternative to theories of practical reason

During the latter half of the 20th century the number of theories being defended in the field of practical reason has proliferated dramatically. This proliferation, however, threatens to undermine the justificatory aim of practical reason, for if these different theories yield different practical inferences, then we seem to be in a dilemma: we have to either give reasons for our reasons, or accept that there aren't any such reasons, which would render our actions (even if they were made after some sort of rational deliberation) completely arbitrary. This thesis argues that currently in the field of practical reason there isn't any method or set form of argumentation aimed at providing reasons for our reasons, and that therefore nihilism, or the view that we don't have good reasons for doing what we do, seems to be the best attitude to take regarding theories of practical reason and human agency. This conclusion is then defended against three objections that stem from the views of J. David Velleman, Christine M. Korsgaard, and John McDowell.