I believe what you're describing is the concept of qualia: http://plato.stanford.edu/entries/qualia/ http://plato.stanford.edu/entries/qualia/ The exact scope

I believe what you're describing is the concept of qualia: http://plato.stanford.edu/entries/qualia/ http://plato.stanford.edu/entries/qualia/ The exact scope of the term is not universal, but it might be well expressed as the atomic level of individual mental experience. Even if we experience the same physical wavelength of light and can address it on the same terms, we may nonetheless have entirely different qualia connecting that physical data and that shared mental construction of the color. And there's no way we would ever know!