Hume begins by shifting focus from the general idea of justice to particular laws, but he says that the focus is the same either way—it's all about what's good and useful for society.
While some religious types have seen justice as something that's defined from above, Hume believes that we need to look at it on a more grounded level. He has no time for religious fanatics, and is relieved that magistrates don't pay much notice to their views. He adds that there were fanatics of this kind in England during the civil wars, but their more extreme views alienated them from the general population. Folk were like, "are these guys for real?"
In addition to religious fanatics, Hume muses on whether we could call the Levellers (who believed in sharing property equally) political fanatics. The kind of equality that they advocated may seem ideal to many, but Hume says that common sense and history have shown that it mostly doesn't work. Mostly.
Expanding on this, Hume says that any equality that's established would most likely crumble given people's different personalities, skills, and circumstances. He suggests, too, that this world of equality wouldn't be as benevolent as we might imagine—when people started to show signs of inequality, authority would step in and we could head down a slippery slope to tyranny. Eek!
On the other hand, in this world of total equality, who could possess authority in the first place? Like property, no one would have any more or less than their neighbor.
Hume concludes that we need to keep in mind the question: what's most useful to society? Hume uses the concept of property to illustrate this, singling out the terms "mine" and "yours." This division is something that we've created because we've found it useful. Easy-peasy.
The definition of property may be simple: it's something that's lawful for a person to own and use. Still, we establish and maintain this through all kinds of customs and laws. For all these complexities though, we always come back to the happiness and welfare of society. It's our ultimate go-to.
Hume has no time for superstitions, noting that an Egyptian wouldn't approach bacon for religious reasons but that there's no reason for this based on medicine, chemistry, or physics (for more bacon-related news, head here). The rules of property may sometimes seem to work in a similar way—it's immoral to live in a house on one side of a river, but since the other side has different laws, it's all good to live there. Huh? This can seem pretty random, but Hume stresses that justice and the interests of society form a kind of moral compass.
Unlike hunger and thirst, Hume recognizes that justice has been constructed because it serves a social purpose. As for authorities such as chancellors and juries, they've likewise come about because we need them.
Whereas birds of the same species build their nests in the same way, human beings have framed their houses differently depending on the time and place. Hume uses this example to show the influence of reason and custom.
Even so, Hume notes that the major outlines of houses tend to stay pretty much the same because people have found them handy (though there are always exceptions—check this out).
Because property and justice are so well-established, we may take them for granted. Ultimately, though, justice is necessary because it supports society as a whole, and this is the same reason why we value stuff like integrity, loyalty, public spirit, and truthfulness.