  The third or Representation argument is different in kind. Hume offers it initially only to show that a passion cannot be opposed by or be contradictory to “truth and reason”; later (T 3.1.1.9), he repeats and expands it to argue that volitions and actions as well cannot be so. One might suppose he means to give another argument to show that reason alone cannot provide a force to resist passion. Yet the Representation Argument is not empirical, and does not talk of forces or impulses. Passions (and volitions and actions), Hume says, do not refer to other entities; they are “original existence[s],” (T 2.3.3.5), “original facts and realities” (T3.1.1.9), not mental representations of other things. Since Hume here understands representation in terms of copying, he says a passion has no “representative quality, which renders it a copy of any other existence or modification” (T 2.3.3.5).  Contradiction to truth and reason, however, consists in “the disagreement of ideas, consider’d as copies, with those objects, which they represent” (ibid.). Therefore, a passion (or volition or action), not having this feature, cannot be opposed by truth and reason. The argument allegedly proves two points: first, that actions cannot be reasonable or unreasonable;  second, that “reason cannot immediately prevent or produce any action by contradicting or approving of it” (T3.1.1.10). The point here is not merely the earlier, empirical observation that the rational activity of the understanding does not generate an impulse in the absence of an expectation of pain or pleasure. The main point is that, because passions, volitions, and actions have no content suitable for assessment by reason, reason cannot assess prospective motives or actions as rational or irrational; and therefore reason cannot, by so assessing them, create or obstruct them. By contrast, reason can assess a potential opinion as rational or irrational; and by endorsing the opinion, reason will (that is, we will) adopt it, while by contradicting the opinion, reason will destroy our credence in it. The Representation Argument, then, makes a point a priori about the relevance of the functions of the understanding to the generation of actions. Interpreters disagree about exactly how to parse this argument, whether it is sound, and its importance to Hume’s project.