Disability Is disability a social construction? Is there a coherent way to define disability at all? — Banno
In the UK there is this definition which seems relevant:
6 Disability
(1) A person (P) has a disability if—
(a) P has a physical or mental impairment, and
(b) the impairment has a substantial and long-term adverse effect on P's ability to carry out normal day-to-day activities. — Equality Act 2010
Although this looks like it has a formal diagnostic element ('impairment') and a functional element, apparently it doesn't in law. A diagnosis isn't necessary although some diagnoses are automatically sufficient. All you really need to show is that there is something about you can name or describe (an 'impairment') that means you are not able to carry out day-to-day activities that most people can manage without much difficulty.
This definition is neutral in terms of the social and medical model. It does require us to come up with a standard of 'normal', but that normality could be in medical terms (P is disabled because of atypical brain function which prevents him doing day-to-day activities) or social (P is disabled because he is in a minority whose day-to-day needs are different and not adapted for by the majority). Where a minority congregate and become the majority, who is disabled and who is not may switch, according to a social conception. At Autscape, neurotypicals can feel very uncomfortable and struggle to integrate in the group.
Regarding the tension between medical and social models, it seems to me the main relevance of the distinction is in deciding what to do about a disability. Sometimes it's better to locate the problem within the disabled individual (medical model) where a relatively simple 'fix' is the best support, e.g. prosthetic limbs, which enables the person to carry out their day-to-day activities. Even then there may be elements of social disability remaining, perhaps the patronising attitudes of others result in the disabled person not developing the skills needed for the day-to-day activities as quickly as they might. The social model is especially necessary for those with invisible disabilities that do not have medical diagnoses, such as autism, where the diagnosis is based on a set of behaviours. On a medical conception, one could suggest that autism is a made-up thing, and as it doesn't really exist, autistic people are delusional and should just snap out of it. Autistic people typically are disabled - there are things they want to do, that most others can do easily, but can't, for example, go to a noisy pub or bar; or wash up before cooking dinner; or change classrooms unexpectedly, etc. The medical model (locating the problem within the autistic person) is useless - there is no pill that autistic people can take, trying harder only works for a limited time before burnout, cognitive behavioural therapy is worse than useless because it teaches them that they can change their abilities by changing their beliefs, and self-hatred results when this fails. The cure for autistic disability is environmental modification - quiet social spaces, avoiding sudden unexpected changes, setting up systems and routines for every task, answering questions with the detail required, and so on.
If a fish jumps out of the water and land on the path and starts exhibiting challenging behaviour, the medical model would have us fit it with artificial lungs and a trolley at great taxpayer expense. Proponents of the social model will pop it back in the water where it is not disabled.