Abstract
Using a specially designed cellular automaton capable of emulating completely the function of a human brain, we explore ways in which counterfactual sensitivity, that is, the ability of a computational system to respond to any valid inputs, relates to discrete-state machine consciousness. In this computational framework, the distinction between a computation and the recording of a computation can be blurred arbitrarily, yet the physical implementation of the computation itself is unchanged. From this, we conclude that a purely computational account of consciousness is unsatisfactory.

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Next output state is “on” if exactly three neighboring cells are on, unchanged if exactly two neighboring cells are on, otherwise “off.”
To remove any question of whether there are “extra” photons in the projected case, we can arrange things so that when projecting onto a unit cell, the total light is the same as the unprojected case, with either source individually brighter than the detection threshold. So when not projecting, each unit cell could output, say, 4 × the photons needed for detection by the neighbors, but when the projector is on, each unit cell could output only 2 × the threshold, with the projector also outputting 2 × the threshold, so that the total brightness is the same for both the projected and unprojected cases. It is also important to remember that the construction of the CA involves the use of a clock signal that indicates when each unit cell is to sample its inputs, and this signal changes only after both photon sources have fully mingled. This means that there can be no notion of which photons “really” indicated the state, since the laws of physics guarantee that all photons of the same wavelength are identical.
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Acknowledgments
Though I cannot say I am persuaded by his conclusions, (e.g., that all reality results from the operation of a universal computer whose mere Platonic existence implies a sort of modal realism), Marchal [12] discusses a thought experiment with projection onto a two-dimensional computer which was an important inspiration for some of the ideas in this paper.
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Muhlestein, M. Counterfactuals, Computation, and Consciousness. Cogn Comput 5, 99–105 (2013). https://doi.org/10.1007/s12559-012-9155-2
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DOI: https://doi.org/10.1007/s12559-012-9155-2