  Another concern about the famous argument about motives is how it could be sound. In order for it to yield its conclusion, it seems that its premise that morality (or a moral judgment) influences the will must be construed to say that moral evaluations alone move us to action, without the help of some (further) passion. This is a controversial claim and not one for which Hume offers any support. The premise that reason alone cannot influence action is also difficult to interpret. It would seem, given his prior arguments for this claim (e.g. that the mere discovery of a causal relation does not produce an impulse to act), that Hume means by it not only that the faculty of reason or the activity of reasoning alone cannot move us, but also that the conclusions of such activity alone (such as recognition of a relation of ideas or belief in a causal connection) cannot produce a motive. Yet it is hard to see how Hume, given his theory of causation, can argue that no mental item of a certain type (such as a causal belief) can possibly cause motivating passion or action. Such a claim could not be supported a priori. And in Treatise 1.3.10, “Of the influence of belief,” he seems to assert very plainly that some causal beliefs do cause motivating passions, specifically beliefs about pleasure and pain in prospect. It is possible that Hume only means to say, in the premise that reason alone cannot influence action, that reasoning processes cannot generate actions as their logical conclusions; but that would introduce an equivocation, since he surely does not mean to say, in the other premise, that moral evaluations generate actions as their logical conclusions. The transition from premises to conclusion also seems to rely on a principle of transitivity (If A alone cannot produce X and B produces X, then A alone cannot produce B), which is doubtful but receives no defense.