Aristotle, Politics 1307a-b

“And since all aristocratic states tend towards oligarchy, the upper classes bicker over wealth–which is the kind of thing that happened in Sparta, where the estates belong to a very few–and it is possible for the ‘nobles’ to do whatever they want to and to combine their families however they’d like. This is how the state of the Locrians fell thanks to marriage with Dionysius, which never would have happened in a democracy or a well mixed aristocracy.

In particular, Aristocracies experience revolutions quietly, through incremental loosening, as I have said before in general about most constitutions, that even a small thing might be the cause of revolutions. For, whenever they alter the laws of the state a little bit, they always follow it up with a less minor change later, until they have changed the entire system.”

Ἔτι διὰ τὸ πάσας τὰς ἀριστοκρατικὰς πολιτείας ὀλιγαρχικὰς εἶναι μᾶλλον πλεονεκτοῦσιν οἱ γνώριμοι (οἷον καὶ ἐν Λακεδαίμονι εἰς ὀλίγους αἱ οὐσίαι ἔρχονται)· καὶ ἔξεστι ποιεῖν ὅ τι ἂν θέλωσι τοῖς γνωρίμοις μᾶλλον, καὶ κηδεύειν ὅτῳ θέλωσιν (διὸ καὶ ἡ Λοκρῶν πόλις ἀπώλετο ἐκ τῆς πρὸς Διονύσιον κηδείας, ὃ ἐν δημοκρατίᾳ οὐκ ἂν ἐγένετο, οὐδ᾿ ἂν ἐν ἀριστοκρατίᾳ εὖ μεμιγμένῃ).

μάλιστα δὲ λανθάνουσιν αἱ ἀριστοκρατίαι μεταβάλλουσαι τῷ λύεσθαι κατὰ μικρόν, ὅπερ εἴρηται ἐν τοῖς πρότερον καθόλου κατὰ πασῶν τῶν πολιτειῶν, ὅτι αἴτιον τῶν μεταβολῶν καὶ τὸ μικρόν ἐστιν· ὅταν γάρ τι προῶνται τῶν πρὸς τὴν πολιτείαν, μετὰ τοῦτο καὶ ἄλλο μικρῷ μεῖζον εὐχερέστερον κινοῦσιν, ἕως ἂν πάντα κινήσωσι τὸν κόσμον.