Hume argument seems to be the following:
1. what confers the moral quality to an action (its moral admirability) is the moral quality of its motive
2. therefore the first motive of the action cannot be a regard to the virtue of that action.
In HUME's words:
'tis evident, that when we praise any action, we regard only the motives that produc'd them, and consider the actions as signs or indications of certain principles in the mind and temper. The external performance has no merit. [...] And the ultimate object of our praise and approbation is the motive, that produc'd them. (p. 477 SBN,p 307 NN)
It appears therefore, that all virtuous actions derive their merit only from virtuous motives [...]. From this principle I conclude, that the first virtuous motive, which bestows a merit on any action, can never be a regard to the virtue of that action, but must be some other natural motive or principle.
This argument seems to me based upon the conflation of two ways in which the moral quality of an action can be understood. If we distinguish them neatly, it is clear that (2) does not follow from (1).
What (1) says is that the moral goodness of the motive is the only thing that confers moral goodness to the action, in the sense of making it admirable or praiseworthy. But this is compatible with thinking that what makes person's p motive to do F a morally good motive is the fact that p F-ed because, in his light, F-ing appeared as just, honest, courageous, or morally required.
Hume's argument seems to require the conflation between:
A. the moral goodness of the action, understood as what makes the action F (or better, the action -type F) just/honest/corageous/required, in the perspective of the agent who F-s
B. the moral goodness of the action, understood as the fact which makes p's F-ing morally admirable, in the perspective of a spectator.
(B looks like a judgment or reaction towards the performance of a particular action, but is really a judgment or reaction towards the character of the agent, grounded in that agent's performance of a particular action. The evaluation of action here is a mere proxi for an evaluation of character, as Hume clearly recognizes.)
We can think (and, I believe, should think) that the moral goodness of an action F, understood as A (what makes the action of type F, in that circumstance, just/honest/courageous), derives at least in part from the circumstances of action, features of the reality outside the agent. At the same time, we may think - without contradiction - that the goodness of the action in the sense of B (what makes admiration or praise towards the the fact that p's F-ed appropriate) is solely a fact concerning p's motive for F-ing, the fact that he chose to F because F appeared to him as what justice/honesty/ or courage required.
Hence the two types of judgment, one concerning the appropriateness of an action, given the circumstances, in the perspective of the agent, and the other concerning the fact that an agent behaved in a praiseworthy way, in the perspective of a spectator, are clearly distinct, and we do not run in a circle, contrary to what Hume argued, by saying that we admire p's performance of F (or p on the ground that he F-ed) because of p's motive, and that what makes p's motive in F-ing a virtuous one, is the fact that p F-ed because he saw F as what virtue required. That is to say, the first motive of a virtous action can be, contrary to what Hume argued, a regard to the (conformity to) virtue of the action itself.
Given that Hume is such a great philosopher, and that he cannot have failed to see this point, could anyone of you explain what is wrong in my distinction or in my interpretation of the argument?