Question Four: On Causes Excusing from Restitution

S. Th. II-II, q. 62, a. 5, ad 1; a. 8, ad 2.

335. Causes excusing from restitution are of two kinds: 1) some excuse for a time, which suspend the obligation of restoring, so that while they endure it as it were sleeps, but when they cease, it again awakens and revives; 2) others excuse in perpetuity, which truly exempt or release from obligation and extinguish the obligation of restoring forever.

The causes excusing for a time are: ignorance - inability - one's own damage - another's damage; but the exempting causes are, besides the destruction of the thing, condonation - compensation - and legitimate authority.