This treatment, which thus proceeded in the ages of barbarism, from the low estimation, in which slaves were unfortunately held from the circumstances of the commerce, did not fail of producing, in the same instant, its own effect.  It depressed their minds; it numbed their faculties; and, by preventing those sparks of genius from blazing forth, which had otherwise been conspicuous; it gave them the appearance of being endued with inferiour capacities than the rest of mankind.  This effect of the treatment had made so considerable a progress, as to have been a matter of observation in the days of Homer.

For half his senses Jove conveys away,
Whom once he dooms to see the servile day.[021]

Thus then did the commerce, by classing them originally with brutes, and the consequent treatment, by cramping their abilities, and hindering them from becoming conspicuous, give to these unfortunate people, at a very early period, the most unfavourable appearance.  The rising generations, who received both the commerce and treatment from their ancestors, and who had always been accustomed to behold their effects, did not consider these effects as incidental:  they judged only from what they saw; they believed the appearances to be real; and hence arose the combined principle, that slaves were an inferiour order of men, and perfectly void of understanding.  Upon this principle it was, that the former treatment began to be fully confirmed and established; and as this principle was handed down and disseminated, so it became, in succeeding ages, an excuse for any severity, that despotism might suggest.

We may observe here, that as all nations had this excuse in common, as arising from the circumstances above-mentioned, so the Greeks first, and the Romans afterwards, had an additional excuse, as arising from their own vanity.

The former having conquered Troy, and having united themselves under one common name and interest, began, from that period, to distinguish the rest of the world by the title of barbarians; inferring by such an appellation, “that they were men who were only noble in their own country; that they had no right, from their nature, to authority or command; that, on the contrary, so low were their capacities, they were destined by nature to obey, and to live in a state of perpetual drudgery and subjugation."[022] Conformable with this opinion was the treatment, which was accordingly prescribed to a barbarian.  The philosopher Aristotle himself, in the advice which he gave to his pupil Alexander, before he went upon his Asiatick expedition, intreated him to “use the Greeks, as it became a general, but the barbarians, as it became a master; consider, says he, the former as friends and domesticks; but the latter, as brutes and plants;"[023] inferring that the Greeks, from the superiority of their capacities, had a natural right to dominion, and that the rest of the world, from the inferiority of their own, were to be considered and treated as the irrational part of the creation.