Reply to Objection 2. In things which are of themselves, reason begins from principles that are known naturally, and advances to some term. Wherefore the Philosopher proves (Poster. i, 3) that there is no infinite process in demonstrations, because there we find a process of things having an essential, not an accidental, connection with one another. But in those things which are accidentally connected, nothing hinders the reason from proceeding indefinitely. Now it is accidental to a stated quantity or number, as such, that quantity or unity be added to it. Wherefore in such like things nothing hinders the reason from an indefinite process.