Ketubot 32 - Corporal punishment or monetary payment?

If one violates his virgin sister, he pays the 50-shekel payment mentioned earlier . However, when we studied the corporal punishment in detail , we said that he gets lashes for the same thing!?

In explaining this, Ulla suggested that the corporal punishment applies because he violated his sister who is somewhat grown up, past 12 ½ (no penalty) and who is moreover mentally deranged (no humiliation payment). And yet, she suffers pain! - We conclude that he seduces her (no pain).

Be that as it may, we see that for Ulla it is really important to defend his principle that if one faces two punishments, lashes and money payment, he should be given the less severe money penalty. But usually we give him the more stringent one, on the theory that the punishment is for the correction of his soul. So where does Ulla get his principle from?

The Talmud tries to derive this from logic (because such a proof would be preferred), but ends up using the comparison based on similar words. The word "tachat" in the sense of "as a compensation for" is used talking about the girl and in the "eye for an eye" - where we know very well that the Torah meant a monetary payment, and not taking his actual eye out .

Art: Sister of the Artist By Christen Kobke