The famous female pop artist, Madonna, once sang, "Cause we're living in a material world, and I am a material girl." While Madonna's song focused on living an affluent life, what if we applied this specific lyric metaphysically? What is the impact on Christianity? Is the totality of our reality just material?
Materialism and Christianity
Materialism states that all that exists is material. In other words, our cosmos, as a whole, is composed of nothing more than particles, molecules, medium-sized objects, planets, stars, and galaxies. The direct implication of this view paints a grim picture for Christianity. If the totality of reality is only material, there is no room for God, the Holy Spirit, souls, etc. If materialism is true, Christianity is false.
Materialism and Knowledge
If everything in our reality is material, how do we acquire knowledge? The Materialist's answer is empiricism. Empiricism is the theory of knowledge that stated the only way we can know anything is through our five senses. Atheist, Alex Rosenberg says,
If we are going to be scientistic, then we have to attain our view of reality from what physics tells us about it. Actually, we'll have to do more than that: we'll have to embrace physics as the whole truth about reality…We trust science as the only way to acquire knowledge.
Notice, what Rosenberg advocates: If you want to know about reality if you want to be informed, you must trust science—not as a way, but as the only way to acquire knowledge.
Problems with Materialism
Rosenberg has made a bold claim. I think he is wrong for two reasons: 1) His statement is self-defeating and 2) There are aspects of the mind which are at odds with metaphysical materialism.
Considering (1), let's look at Rosenberg's proposition, "We trust science as the only way to acquire knowledge." While I can see the sentence on the page or hear the words spoken, propositions themselves aren't measurable in any scientific way. If we change the font and size of the words on the paper, it doesn't matter; the proposition does not change. If we translated the words from English the German, the meaning remains. In essence, the statement, "We trust science as the only way to acquire knowledge" cannot be tested scientifically, and therefore, is self-defeating. On this alone, we should reject materialism.
Reflecting on (2), the first-person perspective regarding the mind is at odds with materialism. When I say that I am in pain, about to go for a run, or I could go for a milkshake right now, I am reporting something about which I cannot be mistaken. The only person who could know these thoughts is me. This seems to be very different from the neurons firing in the brain. You could cut my head open, examine my brain and never access my thoughts.
Furthermore, materialism seems to have no answer for intentionality. By intentionality, I mean the "about-ness" or "of-ness" regarding mental lives. I have a thought of my daughters and about Durham, NC, or contemplate a one-on-one conversation with the apostle Paul, about Jesus. These characteristics of my mental life seem to be more than just an input-output process of materialism. While material, input-output systems can imitate intentionality, they cannot possess it. Additionally, intentionality possesses qualities that physical states do not. For example, intentionality can be about non-existent entities; physical causal relations hold only between existent entities.
There is a distinct difference between the mind and the brain, the mental and the physical. First, to say that science is the only way to access truth is self-defeating. Second, mental properties like first-person perspective and intentionality cannot be reduced to material processes. With these in mind (no pun intended), the seeker of truth should reject metaphysical materialism and strongly consider an alternate explanation for these phenomena, Christianity.
 James K. Dew Jr. and Paul M. Gould, Philosophy: A Christian Introduction. (Grand Rapids: Baker Books, 2019), 93.
 Alex Rosenberg, The Atheist Guide to Reality: Enjoying Life Without Illusions (New York: Norton, 2011), 20.
 Dew and Gould, Philosophy, 94.