The existence and reality of consciousness present one of the most pressing challenges to metaphysical naturalism (the view that only physical things exist). On naturalism, everything that exists should be describable in physical terminology, including properties such as weight, size, and location.
But we all experience certain subjective aspects of the world that resist such explanation. In his book Mind & Cosmos, Atheist philosopher Thomas Nagel explains why consciousness poses such an intractable problem for naturalism:
Consciousness is the most conspicuous obstacle to a comprehensive naturalism that relies only on the resources of physical science. The existence of consciousness seems to imply that the physical description of the universe, in spite of its richness and explanatory power, is only part of the truth, and that the natural order is far less austere than it would be if physics and chemistry accounted for everything. If we take this problem seriously, and follow out its implications, it threatens to unravel the entire naturalistic world picture. Yet it is very difficult to imagine a viable alternative (p. 35).
Naturalists have offered a variety of explanations for consciousness. In the introduction to the updated Evidence that Demands a Verdict, my father and I offer responses to three of the most common ones:
Naturalistic Attempt #1: Behaviorism: Essentially, behaviorists reduce mental attributes to some observable behavior. Nagel offers a cogent response:
It is certainly true that mental phenomena have behavioral manifestations, which supply our main evidence for them in other creatures. Yet all these theories seem insufficient as analyses of the mental because they leave out something essential that lies beyond the externally observable grounds for attributing mental states to others, namely, the aspect of mental phenomena that is evidence from first-person, inner point of view of the conscious subject: for example, the way sugar tastes to you or the way red looks or anger feels, each of which seems to be something more than the behavioral responses and discriminatory capacities that these experiences explain. Behaviorism leaves out the inner mental state itself (p. 38).
Naturalistic Attempt #2: Evolution: On this view, consciousness emerges from the process of natural selection, acting upon random mutation, and offers survival advantages to species.
In The Mysterious Flame, Philosopher Colin McGinn explains why evolution fails to explain consciousness:
But in the case of consciousness the Darwinian explanation does not tell us what we need to know, for the simple reason that it is unclear how matter can be so organized as to create a conscious being. The problem is in the raw materials. It looks as if with consciousness a new kind of reality has been injected into the universe, instead of just a recombination of the old realities. Even if minds showed no hint of design, the same old problem would exist: How can mere matter originate consciousness? How did evolution convert the water of biological tissue into the wine of consciousness?
Naturalistic Attempt #3: Identity: This approach claims the mind and brain are simply two different terms that refer to the same physical reality.
But the problem with this attempt is that physical objects have different properties than mental objects. Mental objects do not have extension in space, weight, or location. And unlike mental states, physical objects cannot be of or about anything. They just are. Therefore, mental states are not identical to physical states.
Consciousness as Evidence for God
There are other naturalistic attempts to explain consciousness, but the reality is that naturalism has no plausible way to explain the emergence of mental properties.
And yet the existence of consciousness makes sense within the theistic worldview. If God is a supremely conscious being, and he has created us, then it makes perfect sense for human beings to be conscious agents who experience the world. God has both the power and incentive to create conscious beings.
The existence of consciousness does not prove God’s existence. But it is undeniable feature of reality that fits a lot more naturally into the theistic worldview.