What I wanted to get at is the value difference between pornographic playing-cards when you're a kid, and pornographic playing-cards when you're older. It's that when you're a kid you use the cards as a substitute for a real experience, and when you're older you use real experience as a substitute for the fantasy.
There's only one good test of pornography.
Get twelve normal men to read the book, and then ask them, Did you get an erection? If the answer is Yes from a majority of the twelve, then the book is pornographic.
What pornographic literature does is precisely to drive a wedge between one's existence as a full human being and one's existence as a sexual being -- while in ordinary life a healthy person is one who prevents such a gap from opening up. Normally we don't experience, at least don't want to experience, our sexual fulfillment as distinct from or opposed to our personal fulfillment. But perhaps in part they are distinct, whether we like it or not.
A perverse nature can be stimulated by anything.
Any book can be used as a pornographic instrument, even a great work of literature if the mind that so uses it is off-balance. I once found a small boy masturbating in the presence of the Victorian steel-engraving in a family Bible.