  Hume offers a rather cryptic argument to show that our approval of material honesty must be the product of collaborative human effort (convention). When we approve an action, he says, we regard it merely as the sign of the motivating passion in the agent’s “mind and temper” that produced it; our evaluation of the action is derived from our assessment of this inner motive. Therefore all actions deemed virtuous derive their goodness only from virtuous motives — motives we approve. It follows from this that the motive that originally “bestows a merit on any action” can never be moral approval of that action (awareness of its virtue), but must be a non-moral, motivating psychological state — that is, a state distinct from the “regard to the virtue” of an action (moral approval or disapproval) (T 3.2.1.4). For if the virtue-bestowing motive of the action were the agent’s sense that the act would be virtuous to do — if that were why he did it, and why we approved it — then we would be reasoning in a vicious circle: we would approve of the action derivatively, because we approve of the agent’s motive, and this motive would consist of approval of the action, which can only be based on approval of a motive... The basis of our approval could not be specified. For every virtue, therefore, there must be some non-moral motive that characteristically motivates actions expressive of that virtue, which motive, by eliciting our approval, makes the actions so motivated virtuous. The virtue of an action of this species would be established by its being done from this non-moral motive, and only then could an agent also or alternatively be moved so to act by her derivative concern for the virtue of the act. However, Hume observes that there is no morally approved (and so virtue-bestowing), non-moral motive of honest action. The only approved, reliable motive that we can find for acts of “equity” is a moral one, the sense of virtue or “regard to the honesty” of the actions. The honest individual repays a loan not (merely) out of self-interest or concern for the well-being of the lender (who may be a “profligate debauchee” who will reap only harm from his possessions), but from a “regard to justice, and abhorrence of villainy and knavery” (T 3.2.1.9, 13). This, however, is “evident sophistry and reasoning in a circle…” Now nature cannot have “establish’d a sophistry, and render’d it necessary and unavoidable…”; therefore, “the sense of justice and injustice is not deriv’d from nature, but arises artificially… from education, and human conventions” (T 3.2.1.17). Whatever, exactly, the logic of this argument is supposed to be, Hume’s intent is to show that if we imagine equity to be a natural virtue we commit ourselves to a sophistry, and therefore honesty is instead man-made.