Israel, D. and Macken, E. and Perry, J. Prolegomena to a Theory of Disability, Inability and Handicapin Logic, Language and Computation, CSLI Press, 1999.
Underlying the political activism that led to the Americans with Disabilities Act (ADA) was what Ron Amundson has called the environmental conception of disability. In  we called this the circumstantial conception of disability and handicap, and contrasted it with the intrinsic conception. We use disability to mean loss of a function, such as moving the hands or seeing, that is part of the standard repertoire for humans. Handicap is a species of inability, in particular, the inability to do something that one wants to do and most others around one can do. The intrinsic conception imagines a tight connection between disability and handicap; the circumstantial conception loosens and relativizes that connection. The circumstantial conception reminds us that we all depend on various tools and structures—in particular, on cultural artifacts—to enable us to do what we want to do. In many cases it is the design of these tools and structures that prevents a disabled person from accomplishing what they want, rather than anything intrinsically connected to the disability. For example, very few people can get from the first floor to the second floor of a building without the assistance of some structure such as stairs, ramps, or elevators. If no such structures are available, everyone is handicapped; if stairs are available, but not a ramp or an elevator, people with various disabilities are handicapped; if ramps or elevators are available, very few people are. Disabled people, like everyone else, are handicapped in the absence of the structures and tools that enable them to perform the tasks they need and want to do.
The ADA, in requiring that employers and others reasonably accommodate disabled workers, reflects this circumstantial conception of disability and handicap. The underlying idea is simply that many of the tasks that are necessary for getting to a job site and then accomplishing what the job requires can be done by individuals with disabilities, given the proper equipment and facilities. The way the disabled worker accomplishes these tasks may differ from the way other workers do. She may, for instance, use a wheelchair rather than walk to get to the job site; she may use a voice recognition tool rather than typing on a keyboard to input to a computer.
Accommodation can be brought about in two ways. Where situations have been designed without consideration for individuals with disabilities, retrofitting is required; e.g. installing ramps or elevators, widening hallways, etc. Far better is the second way: to design with an eye more toward enabling the accomplishments required to satisfy the demands of the task rather than toward enabling a small range of (even widely employed) ways of satisfying those requirements. Providing stairs enables people who can walk to locomote between flights by (something akin to) walking—though it’s still difficult for people who walk with crutches, say. Providing ramps enables both walkers and a wide range of non-walkers to locomote between flights—the former by walking, the latter, in other ways—and it makes it easier for walkers with crutches.
In developing and applying the circumstantial conception of disability, the following basic concepts are clearly central:
- Doing the same thing in different ways.
- Ability, inability, disability.
- Accommodating and enabling by (re)engineering the environment.
In this paper we extend a theory of action, IPT, presented in [5, 6], to try to elucidate these concepts. This attempt at elucidation is itself at most a prolegomena to a study that can usefully feedback into the moral and legal issues involving disabilities. In the concluding section, however, we try to use the concepts we have developed to enunciate a design principle, which we call generic interfacing.
In the next section we review our theory of action; in x3 we extend the theory to capture more adequately the structure of abilities and inabilities. In x4, we closely examine several cases to motivate and illustrate the notion of generic interfacing; in x5, we draw some conclusions.