Reductionism was a fad of the 1920s and few nowadays think it more than sophomoric and a line of maybe teenagers who just now had it occur to them.  Materialism is impossible since what you would have to have now is something sometimes called "physicality-ism", as we now know matter is only a form of energy and energy is pretty much hard to pin down, and may end up being an illusion of vibrations of fundamental strings or some sort of gyrations of space-time and space-time seems to be doing outrageous things. 

Basically atheism has little to say about existence except there is small evidence of a purpose-driven, history involved deity -- certainly not enough to justify it.  The old materialism is "there is only matter and the void." We now know that is untenable.

I watched a fascinating lecture yesterday from Australia which ended with a cartoon she drew showing the scientists on one end showing neurons and neurochemicals and so on doing marvelous things and on the other end showing mind and economics and society and literature and law and music and so on, separated by a big question mark.

That is the difference between an atheist and a theist -- not that the atheist has answers but that they are willing to say they don't know and see no need or reason to insert a divinity into the issues.