
“Philosophy is certainly the medicine of the soul. Its aid is to be sought not from without, as in diseases of the body; and we must labour with all our resources and with all our strength to cure ourselves.”
Est profecto animi medicina, philosophia; cuius auxilium non ut in corporis morbis petendum est foris, omnibusque opibus viribus, ut nosmet ipsi nobis mederi possimus, elaborandum est.
Book III, Chapter III; translation by Walter Miller
Tusculanae Disputationes – Tusculan Disputations (45 BC)