Note 327 — Chapter XVII · LIABILITY.
Reading edition
The distinction between material and formal wrongdoing has long been familiar in moral philosophy. The material badness of an act depends on the actual nature, circumstances, and consequences of it. Its formal badness depends on the state of mind or will of the actor. The madman who kills his keeper offends materially but not formally; so also with him who in invincible ignorance breaks the rule of right. Material without formal wrongdoing is no ground of culpability.