In masturbation there is nothing but loss. There is no reciprocity. There is merely the spending away of a certain force, and no return. The body remains, in a sense, a corpse, after the act of self-abuse. There is no change, only deadening. There is what we call dead loss. And this is not the case in any act of sexual intercourse between two people. Two people may destroy one another in sex. But they cannot just produce the null effect of masturbation.