Imagine a scientist who knows everything about vision. Every neural pathway, every wavelength, every chemical reaction that fires in the brain when you see red. She knows all there is to know about the mechanism. Just one thing: she has lived her whole life in a black-and-white room, and has never seen color with her own eyes. The day she steps outside and sees a red tomato for the first time, will she learn something new? Something all her knowledge didn’t contain?
If the answer is yes, then there’s something in “what it’s like to see red” that isn’t found in any description of the mechanism. And that’s exactly the difficulty.
The easy and the hard
The philosopher David Chalmers split the study of consciousness in two. There are the “easy problems”: how the brain recognizes a face, how memory forms, how a decision is made. Easy not in the sense that they’re simple, they’re very hard technically, but in the sense that we know how to attack them: find the mechanism, done.
And then there’s the “hard problem”: why all that processing is accompanied by an inner experience at all. Why light entering the eye isn’t simply processed in the dark, like in a camera or a computer, but is experienced. There’s red, there’s pain, there’s taste. You could, in principle, describe a brain that does everything yours does without anyone home feeling a thing. The question is why, in you, someone does feel.
Worth marking: there’s also a serious counter-voice. The philosopher Daniel Dennett argues there’s no real “hard problem”, that it’s an illusion arising from the way we look at ourselves, and once we solve all the easy problems the “hard” one will simply evaporate. Not everyone agrees. That, too, is unsettled.
Why it won’t dissolve tomorrow
It’s easy to think “another scientific mystery, one day they’ll solve it.” But the hard problem is different in kind. Every scientific solution we know is a description of a mechanism, what causes what. Subjective experience is the one thing we know not from the outside but from within. And here it isn’t even clear what an answer would look like. We’re not missing one more data point; we’re missing the form of the explanation itself.
Many traditions spoke of an “inner light” or a soul burning in a person, each in its own words. In the Jewish phrasing: “the candle of God is the soul of man.” Not a scientific claim, and clearly not an explanation of a mechanism. But it pointed at that very spot: that there’s something burning from within, and that you can’t describe it only from the outside.
So a question: if you can describe everything your brain does without once mentioning that anything is felt from the inside, where does the “inside” come from?