Sex is already moving in a virtual direction, between widespread access to and use of porn, phone sex, video-interactive sex, sex in virtual worlds, and eventually teledildonics, the use of body suits and tactile equipment controlled from afar. Electronically mediated sex and porn are safer (no diseases or pregnancy), easier (lengthy courtship and foreplay are unnecessary), more convenient (available any time you are) and more likely to be exactly what you want (your partners can be anyone, or anything, you desire, without any physical defects). The virtualization of sex has progressed from the first erotic paintings and photographs to sex in Second Life. Teledildonics is the next step, and it has been around since the early days of the Web. But the equipment has been so crude that it has not provided a very interesting experience for many. In about ten years however I'm sure that Wii-sex will be quite popular.

The growing sophistication of AI and robotics to detect human emotion, anticipate human desires and respond in ways that simulate a human response will also speed the virtualization of sex. People who are too busy, shy, or unappealing, or whose preferences are too elaborate or taboo to reveal to a living person, may turn to robot sex as an alternative. Of course, we will have a serious problem of robot rights if and when machine minds achieve true self-awareness - perhaps a problem of apocalyptic proportions - and this would effect robot sex like everything else. (It would be bad if the first god-like AI was a former sex slave.)

Lots of people are horrified that virtual sex and porn are reducing desire for and tolerance for physical sex, especially with spouses or partners. But I think that this is first a matter of individual preference; many will still prefer body sex. The decline in physical sex will also soon be overcome by neurotechnologies that control and channel sexual desire. Soon, in addition to Viagra, we will have chemicals that increase and channel desire itself. Right now we can chemically castrate pedophiles and turn off their obsessive thoughts about children, along with all of their sex drive. We can stimulate sexual desire in men and women by increasing their testosterone. We can increase feelings of trust and bonding with oxytocin.

Eventually we will be able to directly stimulate the parts of the brain that desire specific partners or experiences. In the future we will be able to specifically turn off sexual thoughts about children, and turn on appropriate sexual thoughts about adults. We will be able to make gays straight, and straights gay, and everything in between. There will be no more necessity for sexual boredom between long term partners. We will be able to wire ourselves to only desire sex with our spouses, to only desire it in-body, and to desire it according to an agreed upon frequency. Or we can turn off our jealousy, and turn up our libidos, if we have agreed to a polyamorous lifestyle.

When we have our brains laced with nano-neural networks (40 years?) we will eventually be able to experience completely virtual body sensation, so we can have equal or better quality sex with partners in virtual reality, or with combinations of virtual reality and material reality; two real people in a virtual space, a virtual partner in a real space, two real and one virtual person in a semi-real space, whatever. Nano-neural networks and new psychopharmaceuticals will also allow us to modify and enhance sexual and emotional experience, to have orgasms as long and hard as we like, or no orgasms, or to have an experience of cosmic love and oneness instead of an orgasm, experienced as a bolt of tingles through every inch of our body.

Also, as we gain complete control over the neurochemistry of sex, love and bonding we can make conscious, explicit choices about our feelings and desires. Just as we have prenuptial contracts for property, partners may agree to lock their love and sexual desire onto their partners for a specified period, or at least go to marital counseling to have adulterous feelings modified. This technology will also be a huge boon for celibate religious orders, who will be able to turn off their mendicants' sexual feelings. (Perhaps not taking your celibacy pill will be the mark of true self-flagellant.) I suspect that as the range of sexual choices expand, and the potential for sexual addiction grows, a lot of people will adopt either strict monogamy or even celibacy, channeling all that energy into other pursuits.

The challenge will be to remain a liberal society as the birth rate drops and the risk of virtual sexual obsessions grows. These neurotechnological controls over sexuality could enable new forms of Puritanism and repression in authoritarian societies, "curing" homosexuals and enforcing monogamy on people against their will. We will have to work hard to defend cognitive liberty and sexual liberalism against the forces of repression, partly by developing the means for people to control and channel their own sexuality. The debates over the limits on sex in virtual worlds is only the beginning.