Letter 73 (§9)

“Therefore the philosopher thinks of the person who makes it possible for him to use and enjoy these things, of the person who exempts him when the state’s dire need summons to arms, to sentry duty, to the defence of the walls, and to the manifold exactions of war; and he gives thanks to the helmsman of his state. This is what philosophy teaches most of all,—honourably to avow the debt of benefits received, and honourably to pay them; sometimes, however, the acknowledgment itself constitutes payment.”