Sex is the one thing you cannot really swindle; and it is the centre of the worst swindling of all, emotional swindling.... Sex lashes out against counterfeit emotion, and is ruthless, devastating against false love.
Man is always something worse or something better than an animal; and a mere argument from animal perfection never touches him at all. Thus, in sex no animal is either chivalrous or obscene. And thus no animal invented anything so bad as drunkeness - or so good as drink.
Ordinary love is mere animal attraction. Otherwise why is the distinction between the sexes? If one kneels before an image, it is dreadful idolatry; but if one kneels before husband or wife, it is quite permissible!
God bids you not to commit lechery, that is, not to have sex with any woman except your wife. You ask of her that she should not have sex with anyone except you -- yet you are not willing to observe the same restraint in return.