David's comment: Stimuli are one aspect of developing consciousness. He certainly doesn't give us a full explanation of consciousness. My bolded section is to point out the automaticity of cell response to stimuli he is suggesting. His essay also shows how the physics of biology is important. > > dhw: He gives us no explanation at all. To me it is self-evident that you cannot have consciousness without something to be conscious of. Stimuli give an organism something to be conscious of.-He is a leading philosopher read widely by others. It was just of general interest to present him as an example of how far we are from explaining consciousness.