The Extended Mind

Twenty pages that opened the discussion about whether the mind ends at the skull. Clark and Chalmers argue through the thought experiment of Otto and his notebook that if an external resource plays the same functional role as an internal cognitive process, it is part of the cognitive system. The paper launched the extended mind thesis and generated four decades of debate across philosophy, cognitive science, and design. For anyone building digital products, the implication is foundational: your tool is not external to the user's mind but potentially constitutive of it. The paper is freely available online and remains essential reading for understanding why the boundary between person and artifact is not where common sense places it.