Programs not universally realizable
Even if it is ture that a pattern of molecule movements on a wall is isomorphic with, for example, the formal pattern of the WordStar computer program, the wall will not support the same counterfactuals as the program.
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If the WordStar program had been given different input, it would have behaved differently. But the wall, which was not engineered to implement WordStar would not respond to different 'input' (that is, a different pattern of molecular organisation) in the same way. So WordStar is not universally realisable.
Jack Copeland, 1993.