Retreat to the physical

If you have an atheistic world-view, it's very hard to even acknowledge the existence of the metaphysical. Does a soul exist? What is meaning? Do abstract things exist?

What I've seen in this case is that such people generally retreat to the physical in some way, usually to some brain chemistry. In a sense, I can't blame them. If you deny the metaphysical, the physical is all you have and the closest thing in the physical world to the spiritual is the brain.

Yet it's a profoundly unsatisfying explanation. It's an attempt to sneak in the numinous and pretending that the cheap knock-off brand is somehow just as good.