There is no generally accepted definition of enhancement. Three definitions in particular are discussed in the research literature, which are briefly explained and discussed below:

1. Enhancement as distinct from therapy.
2. Enhancement as distinct from biostatistically determined normal states.
3. Enhancement as the promotion of well-being.

The first, widespread approach defines enhancement as distinct from therapeutic interventions. Accordingly, enhancement includes all biotechnological interventions that are not carried out on the basis of a medical indication. One difficulty with this definition of enhancement is that it is based on the distinction between health and illness, which is itself controversial. This distinction is also subject to value judgments as to which physical and mental states are still categorized as “normal” or “healthy” and which degree of deviation is understood as “pathological”. In addition, the understanding of health and illness, and therefore also the understanding of therapy, is subject to social change. The accuracy of this definitional approach therefore depends on the accuracy of the underlying concept of therapy.

The second approach is based on the biostatistically determined normal state of certain mental and physical abilities and functions. Accordingly, a medical intervention is to be categorized as therapy if it restores the biostatistical mean value of the impaired function in a person, e.g. the restoration of average hearing ability. Interventions that enable certain functions to be performed beyond the biostatistical norm therefore represent a form of enhancement. Therapeutic measures can thus be uniformly defined by the goal of restoring normality. Another advantage of this approach is that this measurable parameter makes it possible to distinguish therapy and enhancement objectively. However, this definition also involves value judgments in determining what is understood by the respective biostatistical normality, particularly in the case of more complex mental abilities and functions.

The third approach is based on the concept of well-being or, more generally, the concept of the good life. Accordingly, enhancement includes all biotechnological changes that promote well-being and thus increase the probability of leading a good life. Therapy and enhancement are then no longer distinct from each other, as therapy is simply a form of enhancement. One point of criticism of this approach is that the question of the moral permissibility of enhancement measures no longer arises at all, because enhancement is considered positive by definition. Furthermore, it is criticized that well-being and the perception of a good life are very dependent on a person’s subjective feelings and that a uniform understanding of enhancement is therefore hardly possible.

All approaches differ in their fundamental assumptions. However, there is broad agreement that biotechnological means are used for enhancement. Physical and mental education, training, meditation exercises, nutrition and much more can also lead to above-average physical and mental functions or increase well-being; however, due to the lack of use of biotechnological means, such measures are not usually regarded as enhancement