Why does suffering exist? The metabolic pathways of pain and malaise evolved only because they served the inclusive fitness of our genes in the ancestral environment. Their ugliness can be replaced by a new motivational system based entirely on gradients of well-being. Life-long happiness of an intensity now physiologically unimaginable can become the heritable norm of mental health. A sketch is offered of when, and why, this major evolutionary transition in the history of life is likely to occur. Possible objections, both practical and moral, are raised and then rebutted.

Contemporary images of opiate-addled junkies, and the lever-pressing frenzies of intra-cranially self-stimulating rats, are deceptive. Such stereotypes stigmatise, and falsely discredit, the only remedy for the world's horrors and everyday discontents that is biologically realistic. For it is misleading to contrast social and intellectual development with perpetual happiness. There need be no such trade-off. Thus states of "dopamine-overdrive" can actually enhance exploratory and goal-directed activity. Hyper-dopaminergic states can also increase the range and diversity of actions an organism finds rewarding. Our descendants may live in a civilisation of serenely well-motivated "high-achievers", animated by gradients of bliss. Their productivity may far eclipse our own.

Two hundred years ago, before the development of potent synthetic pain-killers or surgical anaesthetics, the notion that "physical" pain could be banished from most people's lives would have seemed no less bizarre. Most of us in the developed world now take its daily absence for granted. The prospect that what we describe as "mental" pain, too, could one day be superseded is equally counter-intuitive. The technical option of its abolition turns its deliberate retention into an issue of political policy and ethical choice.