Offering what will cost you something

Virginity is an ideal which the pagans had no right to misunderstand. For, in theory, they too, honoured it; and it should have commended itself to their heathen instinct for sacrifice. For the point os a sacrifice is that the victim should be spotless, the best of its kind. You must not offer what you can well afford to spare, but what will cost you something. ... In order to give up something to God, we forego not the sinful pleasures whch we have no right to in any case, but the lawful pleasures which he has given us to enjoy if we will.

Ronald Knox, Captive Flames

Talk about setting modern ideas on their ear with an argument that is completely logical.