Until the End of Time: Mind, Matter, and Our Search for Meaning in an Evolving Universe

by Brian Greene

Particles can have mass, electric charge, and a handful of other similar features (nuclear charges, which are more exotic versions of electric charge), but all these qualities seem completely disconnected from anything remotely like subjective experience. How then does a whirl of particles inside a head—which is all that a brain is—create impressions, sensations, and feelings? Philosopher Thomas Nagel gave an iconic and particularly evocative account of the explanatory gap.18 What’s it like, he asked, to be a bat? Picture it: Aloft on a bed of air as you soar across a dark landscape, you cry out with an incessant patter of clicks, generating echoes from trees, rocks, and insects, which allow you to map the environment. From the reflected sound you realize a mosquito is up ahead and darting to the right, so you swoop in and enjoy a tiny morsel. Since our mode of engagement with the world is profoundly different, there is just so far our imagination can take us into the bat’s inner world. Even if we had a complete accounting of all the underlying fundamental physics, chemistry, and biology that make a bat a bat, our description would still seem unable to get at the bat’s subjective “first-person” experience. However detailed our material understanding, the inner world of the bat seems beyond reach.