Masturbation in our society is something of a paradox. On the one hand, it's the most common sexual act globally and locally. It happens more than any other act and for most of us it's the sexual activity we'll do more than anything else in our lifetime. You'd think this would mean that of all the sex we have, masturbation would be the kind we have the most to say about.

But try asking someone what masturbation is. Not how they do it, but in general, what it is. Usually there will be a pause,...