My edition of Plato’s republic dates from 1904 and is edited by James Adam. I was a bit surprised to see his comment on this passage.
καλῶς, ἦν δ᾽ ἐγώ, λέγεις. τί δέ; εἴ τις θεῶν ἄνδρα ἕνα, ὅτῳ ἔστιν ἀνδράποδα πεντήκοντα ἢ καὶ πλείω, ἄρας ἐκ τῆς πόλεως αὐτόν τε καὶ γυναῖκα καὶ παῖδας θείη εἰς ἐρημίαν μετὰ τῆς ἄλλης οὐσίας τε καὶ τῶν οἰκετῶν, ὅπου αὐτῷ μηδεὶς τῶν ἐλευθέρων μέλλοι βοηθήσειν, ἐν ποίῳ ἄν τινι καὶ ὁπόσῳ φόβῳ οἴει γενέσθαι αὐτὸν περί τε αὑτοῦ καὶ παίδων καὶ γυναικός, μὴ ἀπόλοιντο ὑπὸ τῶν οἰκετῶν;
That’s well said, I said but what about this? Supposing there was man with fifty or more slaves and a god should lift him out of the city together with his wife and children and deposit him in the desert with the rest of his possessions and his slaves, how afraid do you think he would be for himself and his wife and children that they would destroyed by the slaves?
Plato Republic book 9 578e
James Adam comments
It is a mistake to suppose from this passage that the treatment of slaves in Athens or Greece generally was exceptionally cruel or unkind. Granted the existence of slavery at all, what Plato here says would nearly always be found true, especially where, as in Athens, the slaves belonged for the most part to an alien and inferior race.
James Adam 1902
My first thought was that to the Greeks James Adam would have belonged to an alien and inferior race and would have been perfect slave material. I also pondered whether slavery was exceptionally cruel and unkind in classical Athens. I suppose that the evidence is that in many cases it was not and that being a slave was not pleasant but at least bearable and in some cases actually afforded opportunities for advancement and you would have had some legal rights. A lucky few got very rich and Athenian citizenship such as Pasio. But there were exceptions to this rule. Probably the worst you could get as a slave was to work in the mines at Laurium where life was hard and short. Those Athenians captured during the expedition to Sicily would have got a taste of their own medicine when they were forced to work in the stone quarries in Syracuse. Another group of slaves were those who were forced into prostitution.
There is another example of what seems extraordinary cruelty. In an Athenian trial, the evidence of a slave was only valid if extracted under torture. The slave could be old or female but still be liable to torture.If one of parties in the trial did not give up their slaves when the slaves might have had some evidence, then this would be used by the opposing side as an admission of guilt. Demosthenes explains the thinking.
ὑμεῖς τοίνυν καὶ ἰδίᾳ καὶ δημοσίᾳ βάσανον ἀκριβεστάτην πασῶν πίστεων νομίζετε, καὶ ὅπου ἂν δοῦλοι καὶ ἐλεύθεροι παραγένωνται, δέῃ δ᾽ εὑρεθῆναι τὸ ζητούμενον, οὐ χρῆσθε ταῖς τῶν ἐλευθέρων μαρτυρίαις, ἀλλὰ τοὺς δούλους βασανίζοντες, οὕτω ζητεῖτε τὴν ἀλήθειαν εὑρεῖν. εἰκότως, ὦ ἄνδρες δικασταί: τῶν μὲν γὰρ μαρτυρησάντων ἤδη τινὲς οὐ τἀληθῆ μαρτυρῆσαι ἔδοξαν: τῶν δὲ βασανισθέντων οὐδένες πώποτ᾽ ἐξηλέγχθησαν, ὡς οὐκ ἀληθῆ τὰ ἐκ τῆς βασάνου εἶπον.
Now you think that both in the private and public sphere torture is the most accurate of all proofs and where there are both slaves and free men and the truth of a question has to be discovered, you don’t use the evidence of the free men but you torture the slaves in order to find the truth. And quite right, men of the jury. For when men give witness statements, some have seemed not to to tell the truth but not one person under torture has been proved not to have told the truth as the result of the torture.
Demosthenes 30 37 against Onetor
To us this seems wrong headed. Surely if someone is being tortured, they will say the thing that will most likely stop the torture whether it is true or not. If they can stand the torture they would surely give evidence on behalf of their master; otherwise they could face punishment when they returned home. Aristotle concurs with this view.
αἱ δὲ βάσανοι μαρτυρίαι τινές εἰσιν, ἔχειν δὲ δοκοῦσι τὸ πιστόν, ὅτι ἀνάγκη τις πρόσεστιν. οὔκουν χαλεπὸν οὐδὲ περὶ τούτων εἰπεῖν τὰ ἐνδεχόμενα, ἐξ ὧν ἐάν τε ὑπάρχωσιν οἰκεῖαι αὔξειν ἔστιν, ὅτι ἀληθεῖς μόναι τῶν μαρτυριῶν εἰσιν αὗται,ἐάν τε ὑπεναντίαι ὦσι καὶ μετὰ τοῦ ἀμφισβητοῦντος, διαλύοι ἄν τις τἀληθῆ λέγων καθ᾽ ὅλου τοῦ γένους τῶν βασάνων:οὐδὲν γὰρ ἧττον ἀναγκαζόμενοι τὰ ψευδῆ λέγουσιν ἢ τἀληθῆ, καὶ διακαρτεροῦντες μὴ λέγειν τἀληθῆ, καὶ ῥᾳδίως καταψευδόμενοι ὡς παυσόμενοι θᾶττον. δεῖ δὲ ἔχειν ἐπαναφέρειν ἐπὶ τοιαῦτα γεγενημένα παραδείγματα ἃ ἴσασιν οἱ κρίνοντες. δεῖ δὲ λέγεινὡς οὐκ εἰσὶν ἀληθεῖς αἱ βάσανοι: πολλοὶ μὲν γὰρ παχύφρονες οἱ καὶ λιθόδερμοι καὶ ταῖς ψυχαῖς ὄντες δυνατοὶ γενναίως ἐγκαρτεροῦσι ταῖς ἀνάγκαις, οἱ δὲ δειλοὶ καὶ εὐλαβεῖς πρὸτοῦ τὰς ἀνάγκας ἰδεῖν αὐτῶν καταθαρροῦσιν, ὥστε οὐδὲν ἔστι πιστὸν
Torture is a kind of evidence, which appears trustworthy, because a sort of compulsion is attached to it. Nor is it difficult to see what may be said concerning it, and by what arguments, if it is in our favor, we can exaggerate its importance by asserting that it is the only true kind of evidence; but if it is against us and in favor of our opponent, we can destroy its value by telling the truth about all kinds of torture generally; for those under compulsion are as likely to give false evidence as true, some being ready to endure everything rather than tell the truth, while others are equally ready to make false charges against others, in the hope of being sooner released from torture. It is also necessary to be able to quote actual examples of the kind with which the judges are acquainted. It may also be said that evidence given under torture is not true; for many thick-witted and thick-skinned persons, and those who are stout-hearted heroically hold out under sufferings, while the cowardly and cautious, before they see the sufferings before them, are bold enough; wherefore evidence from torture may be considered utterly untrustworthy.
Aristotle Rhetoric 1377