  We initially obey our magistrates from self-interest. But once government is instituted, we come to have a moral obligation to obey our governors; this is another artificial duty that needs to be explained. On Hume’s view it is independent of the obligation of promises. We are bound to our promises and to obey the magistrates’ commands on parallel grounds: because both kinds of conformity are so manifestly beneficial for  all. Governors merely insure that the rules of justice are generally obeyed in the sort of society where purely voluntary conventions would otherwise break down. As in the case of fidelity to promises, the character trait of allegiance to our governors generates sympathy with its beneficiaries throughout society, making us approve the trait as a virtue.