Neuroscience has made remarkable progress. We can map which regions of the brain activate during perception, emotion, memory, and decision-making. We can trace the neural correlates of almost any mental state. We can intervene in the brain — with drugs, electrical stimulation, surgical lesion — and produce predictable changes in experience and behaviour.
What neuroscience cannot explain is why there is any experience at all.
The easy problems and the hard problem
Philosophers of mind distinguish between what one philosopher called the “easy problems” and the “hard problem” of consciousness. The easy problems — not easy in practice, but easy in principle — concern the functional and behavioural aspects of mind: how the brain processes information, integrates data from different sensory systems, directs attention, controls behaviour. These are difficult scientific problems, but they are the kind of problems that, in principle, more data and better theories can solve.
The hard problem is different. It asks: why is there subjective experience at all? Why, when light of a certain wavelength hits your retina and triggers a cascade of neural activity, do you see red — why is there something it is like to have that experience? Why is there an “inside” to consciousness, a qualitative feel, rather than mere information processing in the dark?
You know there is an inside to your experience. You know what red looks like to you, what pain feels like, what the taste of coffee is. These qualitative properties — philosophers call them qualia — are the most intimate facts of your existence. And they are the facts that physical science, in its current form, has no account of.
Why the gap matters
The standard response is that we will eventually explain consciousness in physical terms — that it will turn out to be identical to, or reducible to, or emergent from, physical brain states. The history of science shows us reducing apparently non-physical phenomena to physical ones: heat to molecular motion, life to chemistry, inheritance to DNA.
But the consciousness case is different in kind, not just degree. When we explained heat as molecular motion, we explained everything about heat — there was no residue, no unexplained element. When we attempt to explain consciousness as brain activity, there is always a residue: why does this brain activity feel like anything? The explanatory gap does not close as we learn more about the brain. It becomes more clearly defined.
One philosopher — himself an atheist — concluded in a widely discussed book that standard materialism cannot account for consciousness, and that something is missing from the standard picture of the natural world. Not a supernatural something — he is not a theist — but a fundamental feature of reality that physical science does not currently describe. He describes this as a reason for thinking that “the world is not entirely captured by physics.”
What this points toward
The hard problem does not prove that God exists. But it does create serious difficulty for the view that the physical universe is all there is. If consciousness — the most immediately known thing in existence — cannot be reduced to physical processes, then the universe contains more than physics describes. And if it contains more than physics describes, the confident claim that “science has shown there is no room for God” becomes much harder to sustain.
A universe that contains irreducibly non-physical consciousness is a universe in which the mental is fundamental, not derived. And a universe in which the mental is fundamental is not a universe that points away from a conscious creator — it is one that is at least as consistent with the existence of such a creator as with any alternative.