The Extrinsic Title

Aquinas taught against interest on loans, even though there was explicit teaching against it. If you were a merchant who made your living and supported your family by taking money and using that to finance these merchant trips where you go to some land, buy something, bring it to another market where it's more expensive,. That's what you do for a living. It seems to me patently unjust to discount the profits that that merchant expected to make because I mean, that is his livelihood. He could demand interest up to whatever it would cost him to rent a down mattress during the duration of the loan. Because by rights, he ought to have it.