If we, as humans, are only physical systems (merely matter), we ought to stop trying to hold each other accountable for misbehavior. In fact, there can be no misbehavior if we are only physical brains and bodies; there can only be behavior. Our actions have no moral content at all unless we truly have the freedom to choose and the ability to break the bondage of physical event causation. As a homicide detective, I can’t prosecute the gun or knife that was used by the murderer, but I can certainly arrest the free-agent human that used the physical tool to commit the murder in the first place. I can’t do this if the human was only another purely physical object in a sequence of caused events. If materialism (physicalism) is true, there is no need for homicide detectives. We still employ detectives, however, because our sense of moral obligation proves materialism to be false.
–J. Warner Wallace