A No-Go Theorem for Process Theories of Consciousness

<p>Many influential theories identify consciousness with temporally extended processes: global broadcasting, recurrent processing, predictive updating, computation. We show that such theories cannot be maintained alongside two commitments that scientific practice ordinarily assumes. The first is that a system's subsequent behaviour is fixed by its present physical condition together with influences crossing its boundary — the assumption underwriting experimental replicability, since preparing the same system under the same conditions is expected to yield the same result. The second is that consciousness makes some difference to what a system does, without which no experimental intervention can identify which attribution is correct. Two systems may reach the same present state by different routes. If consciousness depends on which route was taken, that difference either alters subsequent behaviour, contradicting the first commitment, or alters nothing and no experimental intervention can detect it. Consciousness must therefore be attributed to a system’s present state rather than to its past states. This holds for any system whose complete present local state, together with influences crossing its boundary, determines its subsequent evolution, which includes all systems whose relevant fundamental dynamics are captured in principle by models from classical physics.</p>