Laudator Temporis Acti

Plato, Laws 862e-863a (tr. Trevor J. Saunders):

But suppose the lawgiver finds a man who's beyond cure — what legal penalty will he provide for this case? He will recognize that the best thing for all such people is to cease to live — best even for themselves. By passing on they will help others, too: first, they will constitute a warning against injustice, and secondly they will leave the state free of scoundrels. That is why the lawgiver should prescribe the death penalty in such cases, by way of punishment for their crimes — but in no other case whatever.

ὃν δ᾽ ἂν ἀνιάτως εἰς ταῦτα ἔχοντα αἴσθηται νομοθέτης, δίκην τούτοισι καὶ νόμον θήσει τίνα; γιγνώσκων που τοῖς τοιούτοις πᾶσιν ὡς οὔτε αὐτοῖς ἔτι ζῆν ἄμεινον, τούς τε ἄλλους ἂν διπλῇ ὠφελοῖεν ἀπαλλαττόμενοι τοῦ βίου, παράδειγμα μὲν τοῦ μὴ ἀδικεῖν τοῖς ἄλλοις γενόμενοι, ποιοῦντες δὲ ἀνδρῶν κακῶν ἔρημον τὴν πόλιν, οὕτω δὴ τῶν τοιούτων πέρι νομοθέτῃ κολαστὴν τῶν ἁμαρτημάτων θάνατον ἀνάγκη νέμειν, ἄλλως δὲ οὐδαμῶς.