As to experiencing/conceptualizing a gradation of consciousness, just keep drinking alcohol till you black out.  Somewhere in there is a gray area.,(reply>), ​@zack whitehead But that's not his point. The point is what happens if you show the same spectrum to two different people, or more generally - do different conscious beings have the same subjective experience of the same objective phenomenon? ... No, they don't, obviously.<br><br>We can assume that two beings of the same general construction (e.g. two people) will have very similar subjective experiences. (We do that anyway on regular basis.) But the more difference there is between the two beings the bigger difference there will be between their subjective experiences - even though the original phenomenon is the same.<br><br>A color-blind person will see a red apple differently than a color-seeing person. Even though the spectrum of the light reflecting from the apple is the same for both they will have different subjective experiences of it. And a blind person will not have any experiences related to that spectrum at all. Surely you're not implying that the apple doesn't exist for them..,(reply>), @Justin Brown red is a set criteria of spectrum. If I show you two identical spectra, you'll likely interpret them as such. I'm no dualist, if you can't measure it it doesn't exist, and if it doesn't predict anything it isn't scientific theory.,(reply>), If "Red" is an illusion created by the mind to represent a specific light spectrum, do we all see the same "Red"?  What about for different species?  If "Pain" is a signal from nerves alerting us of tissue damage, and it is also an illusion, do we all feel pain the same way?  What about in different species?  Maybe consciousness isn't just on a gradation, maybe it is on a spectrum.  Maybe one consciousness is a totally different "flavor" from another type of consciousness.