Hume and mankind's bias

In an audio presentation about "artifice and society in the work of Hume" (recorded anthology of French Thought), Gilles Deleuze demonstrates that for David Hume, man is not selfish but biased. That means that he has a sphere of privileged sympathy.
For Hume, there are three types of sympathy: with close relations, with parents and with fellow human beings. They match the three principles of association which he identified in his works (particularly on association of ideas): similarity, continuity and common causation.
The moral problem then is not to manage selfishness (which is the starting point of the contract often said to be the base of society and institutions, in particular with his XVIIIth century contemporaries), but rather to go beyond the circle of natural sympathies to expand it to the whole society. For Hume, the legislation no longer prevents selfishness (which has not been statisfying till now) but overcomes our biases more constructively to expand the circle (not for the contract anymore but for what Hume called the "main rule").