Technologies are not mere external utilities, but are profoundly involved within human development. Explanation of such involvement takes various forms. Like natural and social artefacts, technologies have a historical development, and can acquire metaphysical baggage. One way to conceptualise technology is prosthesis: a tool—from a flint or a hammer, to language —that extends or enables capacities. I’ll discuss prosthesis as a human-technology relation, and consider three such conceptualisations—instrumentalism, Bernard Stiegler’s originary technicity, and Gilbert Simondon’s concretisation—and discuss their relevance to and potential for thinking about disability.