Why might science never fully explain what it feels like to be you?

Because explaining what a brain does may never explain why any of it feels like something. That is the "hard problem of consciousness", a name the philosopher David Chalmers coined in a 1994 talk in Tucson, Arizona. Picture stubbing your toe. Science can, in principle, trace the nerve signals from your toe to your brain, the processing, and the yelp. Chalmers called those the "easy problems", tongue in cheek, since they're about as easy as going to Mars. The hard problem is why all that machinery comes with the feeling of pain at all, and why it feels the way it does.

To sharpen the point, philosophers imagine a "zombie": a being physically identical to you, atom for atom, that behaves exactly like you but has no inner experience. If such a thing is even logically possible, then the physical facts alone don't seem to settle the facts about experience.

Not everyone buys it. The philosopher Daniel Dennett and others argue the hard problem isn't real, and some go as far as calling our sense of inner experience a kind of illusion. Most neuroscientists expect the puzzle to dissolve as the easy problems get solved. Still, in a 2020 survey, about 62 percent of philosophers said the hard problem is real.

One famous bet shows how stubborn it is. The neuroscientist Christof Koch made a 25-year bet with Chalmers that the brain basis of consciousness would be well understood by 2023. In 2023, Koch lost and handed over a case of fine wine.