Physicalism, broadly defined, is the belief that all that exists are physical properties. Many non-Christians object to the truth of Christianity on the basis of this belief – “there’s no such thing as a ‘god’. All that exists are atoms and things that can be explained by science.” A physicalist has no room for non-physical stuff like a spirit.
The following is a philosophy essay that was written to address the question of whether physicalism is a provable stance to take when it comes to an understanding of our bodies and, specifically, our minds. The essay argues that physicalism cannot be proved in any meaningful way but can only be assumed. The point for Christians is that anyone who says that they believe only physical things exists can be challenged in this belief. They can’t prove it! All they can do is assume it.
The essay contains technical language and is not written from a Christian perspective (though, it is written by a Christian author).
Essay Link: Physicalism