6 ideas
The easy problems of consciousness concern explaining functions such as discrimination, integration, reportability, and control of behavior, and each yields to specifying a mechanism that performs the function. The hard problem asks why the performance of these functions is accompanied by subjective experience at all. Even a complete functional account leaves this question open, so it cannot be solved by the same method.
A zombie is a being physically identical to a conscious human but with no experience. If such a world is coherently conceivable, and conceivability here implies logical possibility, then consciousness does not logically supervene on the physical. Physicalism, which requires that fixing the physical facts fixes all facts, is therefore false.
B-facts logically supervene on A-facts if no possible world could duplicate the A-facts without duplicating the B-facts. They naturally supervene if the dependence holds only because of the laws of our world. Reductive explanation requires logical supervenience, and consciousness fails that test. Its dependence on the physical is therefore a matter of contingent natural law.
Because experience cannot be derived from physics, it should be treated as a fundamental feature of the world, like mass or charge. Its connection to physical processes is then governed by basic psychophysical bridging laws. This makes the view a property dualism that stays scientific: consciousness is lawful and systematically studyable, just not reducible.
Chalmers proposes two constraints on any theory of consciousness. Structural coherence holds that the structure of experience mirrors the structure of awareness, the information available for global control. Organizational invariance holds that any two systems with the same fine-grained functional organization have qualitatively identical experiences, whatever their substrate. The fading and dancing qualia thought experiments defend the second principle by showing that gradually swapping neurons for silicon cannot plausibly change experience while behavior stays fixed.
Information may have two aspects: a physical one, embodied in the difference structures of physical processes, and a phenomenal one, realized as experience. On this view, wherever there is information-processing there may be some experience. That suggests consciousness could be very widespread, even extending to simple systems like thermostats.