Biomedical technologies, such as drugs and surgical techniques, can increasingly be used not only to combat disease, but also to augment the capacities of normal, healthy individuals, a practice commonly referred to as biomedical enhancement. The best-established examples of biomedical enhancement are cosmetic surgery and doping in sports. But most recent scientific attention and ethical debate focuses on extending lifespan, lifting mood, and augmenting intellectual capacities. A number of drugs used to treat narcolepsy and attention deficit hyperactivity disorder have already been shown to have small enhancing effects on attention and memory in normal individuals, and there are range of drugs and other biomedical techniques on the horizon that hold out promise for more dramatic effects. One such technique is brain-machine interfacing, which some predict may allow human brains to be connected directly computers to improve our information processing abilities.

Over the last decade, biomedical enhancement has become the focus of one of the liveliest and widest-ranging debates in practical ethics. In 2003, President Bush’s Council on Bioethics published a report which raised a barrage of ethical concerns about biomedical enhancement. Two former members of the council, Michael Sandel and Leon Kass, even argued that biomedical enhancement is always ethically objectionable, and that biomedical technologies should be used only to combat disease. In response to claims such as these, a number of authors have come to the defence of biomedical enhancement, arguing that it would often be ethically permissible, or even desirable. Transhumanists argue that we should pursue certain kinds of biomedical enhancement even to the point that we are no longer recognizably human.

Those who universally object to biomedical enhancement may have public opinion on their side; the few surveys of the general public conducted to date have found considerable reluctance to countenance biomedical enhancement. However, it is unclear whether there are sound arguments to back up these concerns. One challenge is to explain how biomedical enhancement differs, in an ethically important way, from ordinary biomedical treatments, which are normally regarded as by-and-large unproblematic. Suppose two individuals have an IQ of 100, but the first previously had an IQ of 150, but then suffered a serious head injury, whereas the second has always had an average IQ. Increasing the IQ of the first person would conventionally count as a treatment, whereas increasing the IQ of the second would not. Yet it is not clear that there is any ethically significant difference here.

On the other hand, defenders of enhancement must confront the widespread assumption that biomedical enhancements are ‘zero-sum’ goods, conferring some advantages on those who use them, but also offsetting competitive disadvantages on those who remain unenhanced. They have sought to do this in various ways: some point out that widespread cognitive enhancements might increase the rate of scientific progress, thus benefitting almost everyone; others draw parallels with non-biomedical innovations like agriculture and information technology, suggesting that biomedical enhancements will increase overall human productivity, and can thus be seen as part of the story of human economic development; others present biomedical enhancement as a potential solution to human moral limitations like xenophobia and limited altruism; and others still outline how biomedical enhancements could improve the performance surgeons, pilots, jurors and others performing socially critical functions.