Laudator Temporis Acti

Euripides, fragment 421 (tr. Christopher Collard and Martin Cropp):

... in a hollow cave, without a lamp, like a beast, alone ...

κοίλοις ἐν ἄντροις ἄλυχνος, ὥστε θήρ, μόνος

According to an ancient biography, Euripides was a part-time cave-dweller. See David Kovacs, Euripidea (Leiden: Brill, 1994), pp. 6-7:

They say that he fitted out a cave on Salamis opening on the sea and that he passed his days there avoiding the crowd; and that is the reason he takes most of his similes from the sea.

φασὶ δὲ αὐτὸν ἐν Σαλαμῖνι σπήλαιον κατασκευάσαντα ἀναπνοὴν ἔχον εἰς τὴν θάλασσαν ἐκεῖσε διημερεύειν φεύγοντα τὸν ὄχλον· ὅθεν καὶ ἐκ θαλάσσης λαμβάνει τὰς πλείους τῶν ὁμοιώσεων.

Likewise Aulus Gellius 15.20.5 (tr. Kovacs, pp. 28-29):

Philochorus reports that there is a foul and horrible cave on the island of Salamis, which I have seen, in which Euripides used to write his tragedies.

Philochorus [FGrH 328 F 219] refert in insula Salamine speluncam esse taetram et horridam, quam nos vidimus, in qua Euripides tragoedias scriptitarit.

On ὥστε θήρ, μόνος in the fragment of Euripides cf. Aristotle, Politics 1.1253a29 (tr. H. Rackham):

A man who is incapable of entering into partnership, or who is so self-sufficing that he has no need to do so, is no part of a state, so that he must be either a lower animal or a god.

ὁ δὲ μὴ δυνάμενος κοινωνεῖν ἢ μηδὲν δεόμενος δι' αὐτάρκειαν οὐθὲν μέρος πόλεως, ὥστε ἢ θηρίον ἢ θεός.

What Rackham translates as "a lower animal" is really "a wild beast" (θηρίον). See also Nietzsche, Twilight of the Idols (Maxims and Arrows 3, tr. Walter Kaufmann):

To live alone one must be a beast or a god, says Aristotle. Leaving out the third case: one must be both — a philosopher.

Um allein zu leben, muss man ein Thier oder ein Gott sein — sagt Aristoteles. Fehlt der dritte Fall: man muss Beides sein — Philosoph.