 Externalism about beliefs and other propositional attitudes, and also about perceptual experiences, was alluded to in subsections 3.1 and 3.2. Premise P1 of our much-scrutinized  Argument B—‘Neither Invert nor Nonvert is misperceiving the color of the tomato’—was supported, in part, by a particular externalist theory of perceptual content. According to the externalist, some representational properties of subjects, like the property of believing that water is wet, or that arthritis is painful, or the property of having an experience of something’s looking red, are extrinsic: these properties are not necessarily shared between perfect duplicates (or even less-than-perfect duplicates with perfectly duplicated  brains).[48]  Smith may believe that water is wet, yet twin-Smith on Putnam’s Twin Earth does not believe that water is wet. The tomato may look red to Jones, yet not to twin-Jones on Inverted Earth. (In an alternative scenario, twin-Jones has just been created by happenstance in a swamp: see Davidson 1987.)