Plato, Letters 358a

ἄλλως τε καὶ εἴ τις ἕλοιτο τοιαῦτα πράττειν οἷα καὶ σύ, σχεδὸν παντὶ δῆλον· ἀλλὰ κἀκεῖνο δεῖ σε ἐνθυμεῖσθαι, ὅτι ἕκαστος ἡμῶν οὐχ αὑτῷ μόνον γέγονεν, ἀλλὰ τῆς γενέσεως ἡμῶν τὸ μέν τι ἡ πατρὶς μερίζεται, τὸ δέ τι οἱ γεννήσαντες, τὸ δὲ οἱ λοιποὶ φίλοι, πολλὰ δὲ καὶ τοῖς καιροῖς δίδοται τοῖς τὸν βίον ἡμῶν καταλαμβάνουσι. καλούσης δὲ τῆς πατρίδος αὐτῆς πρὸς τὰ κοινά, ἄτοπον ἴσως τὸ μὴ ὑπακούειν·

especially when the business one chooses is such as yours; yet you ought also to bear in mind that no one of us exists for himself alone, but one share of our existence belongs to our country, another to our parents, a third to the rest of our friends, while a great part is given over to those needs of the hour with which our life is beset. And when our country itself calls us to public duties, it were surely improper not to hearken to the call ; for to do so will involve the further consequence of leaving room