I had said previously that when Hume talks of slavery he often isn't thinking of slavery but oppression under tyranny. On further reflection, though, I was forgetting the passage in the essay on the Populousness of Ancient Nations. It's worth quoting in full. It's an aside, it's only one passage, it still considers the matter only under the rubric of tyranny, and it doesn't address at all the larger issues of race and how "the unhappy part of the species" should be treated instead. And it is full of a common Humean type of ambiguity, where it isn't always clear whether a sentence is a conclusion, an aside, a restatement, or a qualification (which is one of the big reasons why Hume, who seems to write so clearly, is so very difficult to interpret). But, while I don't want to soft-pedal Hume's absurdities on this topic (they are too often soft-pedalled, since it is a real and important question as to just how these absurdities cohere with Hume's general principles), I also don't want people going away with an unbalanced view of his position.
The chief difference between the domestic economy of the ancients and that of the moderns consists in the practice of slavery, which prevailed among the former, and which has been abolished for some centuries throughout the greater part of EUROPE. Some passionate admirers of the ancients, and zealous partizans of civil liberty, (for these sentiments, as they are, both of them, in the main, extremely just, are found to be almost inseparable) cannot forbear regretting the loss of this institution; and whilst they brand all submission to the government of a single person with the harsh denomination of slavery, they would gladly reduce the greater part of mankind to real slavery and subjection. But to one who considers coolly on the subject it will appear, that human nature, in general, really enjoys more liberty at present, in the most arbitrary government of EUROPE, than it ever did during the most flourishing period of ancient times. As much as submission to a petty prince, whose dominions extend not beyond a single city, is more grievous than obedience to a great monarch; so much is domestic slavery more cruel and oppressive than any civil subjection whatsoever. The more the master is removed from us in place and rank, the greater liberty we enjoy; the less are our actions inspected and controled; and the fainter that cruel comparison becomes between our own subjection, and the freedom, and even dominion of another. The remains which are found of domestic slavery, in the AMERICAN colonies, and among some EUROPEAN nations, would never surely create a desire of rendering it more universal. The little humanity, commonly observed in persons, accustomed, from their infancy, to exercise so great authority over their fellow-creatures, and to trample upon human nature, were sufficient alone to disgust us with that unbounded dominion. Nor can a more probable reason be assigned for the severe, I might say, barbarous manners of ancient times, than the practice of domestic slavery; by which every man of rank was rendered a petty tyrant, and educated amidst the flattery, submission, and low debasement of his slaves.
According to ancient practice, all checks were on the inferior, to restrain him to the duty of submission; none on the superior, to engage him to the reciprocal duties of gentleness and humanity. In modern times, a bad servant finds not easily a good master, nor a bad master a good servant; and the checks are mutual, suitably to the inviolable and eternal laws of reason and equity.
The custom of exposing old, useless, or sick slaves in an island of the TYBER, there to starve, seems to have been pretty common in ROME; and whoever recovered, after having been so exposed, had his liberty given him, by an edict of the emperor CLAUDIUS; in which it was likewise forbidden to kill any slave merely for old age or sickness. But supposing that this edict was strictly obeyed, would it better the domestic treatment of slaves, or render their lives much more comfortable? We may imagine what others would practise, when it was the professed maxim of the elder CATO, to sell his superannuated slaves for any price, rather than maintain what he esteemed a useless burden.
The ergastula, or dungeons, where slaves in chains were forced to work, were very common all over ITALY. COLUMELLA advises, that they be always built under ground; and recommends it as the duty of a careful overseer, to call over every day the names of these slaves, like the mustering of a regiment or ship's company, in order to know presently when any of them had deserted. A proof of the frequency of these ergastula, and of the great number of slaves usually confined in them.
A chained slave for a porter, was usual in ROME, as appears from OVID, and other authors. Had not these people shaken off all sense of compassion towards that unhappy part of their species, would they have presented their friends, at the first entrance, with such an image of the severity of the master, and misery of the slave?
(He gives several more examples of ancient slavery, but they don't clearly add anything to the argument. In a footnote, however, he does suggest a causal chain in which contempt for slaves causes a taste for gladiatorial combat, which in term is "a great cause of the general inhumanity of their princes and rulers.")
