A Beginner’s Guide to the Argument from Rationality


Many atheists are committed to explaining every aspect of life in purely material terms. Thus when it comes to the mind and thought, they seek to reduce this most profound of human experiences to the interaction of chemicals and the firing of synapses. The human brain becomes, quite literally, a “meat computer”.

For example, biologist Susan Blakemore, a committed atheist, writes:

If you think that we humans have some special faculty of creativity or consciousness or sentience then I disagree … We are meme machines … and without any consciousness, free will, or other spooky power that might enable to leap outside the system.[1]

Whilst American philosopher Daniel Dennett is equally forthright in his commitment to atheistic materialism.

There is only one sort of stuff, namely matter—the physical stuff of physics, chemistry, and physiology—and the mind is somehow nothing but a physical phenomenon. In short, the mind is the brain … we can (in principle!) account for every mental phenomenon using the same basic principles, laws, and raw materials that suffice to explain radioactivity, continental drift, photosynthesis, reproduction, nutrition, and growth.[2]

Did you grasp quite what Dennett said there? All that you are—your hopes and dreams, your beliefs and your values and above all, your thinking and your reasoning—are nothing more than the movement of atoms jostling together, chemicals fizzing, neurons buzzing. Physics can explain your beliefs with the same ease as it can explain earthquakes or plant growth.

But isn’t there a major problem here? Not least of which is that continental drift and photosynthesis are not rational. I don’t know about you, but I have never once thought to enquire of a newly grown leaf’s view of politics or seek the advice of continental plates on the finer points of Shakespearian sonnets. If Dennett is right, something follows: those things are not rational, therefore neither are we.

But let’s stick with Dennett’s line of thought for a moment—because he is grappling with a difficult puzzle for an atheist. What precisely is a thought, if materialism is true? Presumably a thought has to be a material process, but how does that work exactly? In particular, one of the key things about a thought is that thoughts have an “aboutness” quality to them—indeed, a thought, arguably, is the only thing in the known universe that is about something other than itself. How do we account for that with materialism?

The simple answer is that we can’t. If atheistic materialism is true, our brains evolved, evolution selecting over millions of generations not for truth, but for adaptability. Anything that helps us survive, is selected for, that which doesn’t, gets weeded out.

To illustrate the problem here, a little thought experiment.[3] Consider Sid and Eric, two of our ancient cavemen ancestors. One day, Sid and Eric look up and see, pacing toward them, a hungry-looking sabre toothed tiger. Immediately, they both break into a run, escape and live to survive, and enjoy whatever cavemen do during retirement. However, there is a difference between them. Sid runs away from the tiger because he believes it wishes to eat him. Eric runs away because he loves sabre-toothed tigers, and furthermore believes that the best way to make a tiger really happy is to give it a healthy sprint across the Serengeti. One set of beliefs is true, one is false, but evolution doesn’t care what Sid or Eric believe—merely that they each pump their little legs as fast as their cardiovascular systems can support.

In short, evolution selects for adaptive behaviour. It does not select for truth. Listen to atheist Patricia Churchland:

Boiled down to the essentials, a nervous system enables the organism to succeed in…. feeding, fleeing, fighting and reproducing … Truth, whatever that is, definitely takes the hindmost.[4]

In short, on naturalism you have absolutely no good reason to trust your thoughts. None whatsoever. There is no good reason to assume that they deliver truth. As atheist Thomas Nagel writes:

An evolutionary explanation of our theorizing faculty would provide absolutely no confirmation of its ability to get at the truth. [5]

So what about Christianity? Why do Christians believe that we trust our thoughts, our thinking, and our beliefs? Quite simply because the Christian story is very different to the naturalist story. As Christians, we believe that we are created in the image of a God who is rational and who has created us with the ability to reason, to think, to discern. In the Christian story, we are not merely survival-directed creatures who have evolved by the blind forces of natural selection, but truth-directed beings created in the image of a God who is Truth.

But crucially, God has not merely made us image bearers, but has placed us into a rational, ordered world in which things like science are even possible. It is because of who we are and whose image we bear that we can trust the veracity of our observations and deductions, and trust that we can know truth.

By contrast, when atheists reject God and reduce of all human experience to physical processes, they often end up with a form of determinism—everything in the world, including all of human experience, is simply physically determined by the movement of atoms and particles. This is a view of the world that has some profound and terrible consequences.

The first consequence is that if determinism is true, there can be no such thing as freedom, at least no genuine freedom. You may think that you have freely chosen to be an atheist, or to be a Christian, but actually you had no choice in the matter. You don’t choose your beliefs because they are true or false; you choose them because of the deterministic movements of atoms and particles.

The second consequence is that the determinism which atheistic materialism implies destroys any possibility of real thinking. This is because thinking requires freedom—it requires you to come to a conclusion not because of a chain of chemical processes, but because you believe the conclusion to be true: logically and rationally. It’s fascinating, isn’t it, that every human society has been concerned with the pursuit of truth—pursuing truth seems to be profoundly and deeply part of what being human means. If this doesn’t make sense on atheism, I would suggest that it’s a strong clue that atheism isn’t true. Thinking and rationality point to the fact that the deepest reality in the universe is not just atoms and particles.

In all of this discussion, I’m reminded as we draw to a close of something that the philosopher Mary Midgley once wrote. Midgley was an atheist, but a thoughtful and reflective one, willing to recognise many of the difficulties of atheism—and what atheists risked losing when they threw God away. Midgeley remarked:

“It is all very well to eliminate God from the intelligible universe but eliminating ourselves from it blocks all sorts of enquiries.”[6]

Because when we reject God, who is the ground of our being, we undercut precious aspects of our own humanity. In contrast, the Christian faith offers a coherent account of our humanity, notably our capacity for rationality: one of the most precious gifts that the creator God has given us and one of the many means through which we can come to know him. As Jesus said: “Love the Lord your God with your heart, soul and mind”.

Dr Andy Bannister is the Director of the Solas Centre for Public Christianity, and the author of The Atheist Who Didn’t Exist.

Further Reading:

Moderate level:  “Am I Just My Brain?” by Sharon Dirckx (available here)

More advanced level: “Where the Conflict Really Lies” by Alvin Plantinga. (available here)


[1]        Susan Blackmore, ‘Copy That: A Response’. The New York Times, 3 September 2010 (http://opinionator.blogs.nytimes.com/2010/09/03/copy-that-a-response/) (http://opinionator.blogs.nytimes.com/2010/09/03/copy-that-a-response/, accessed 27 July 2011).

[2]        Daniel Dennett, Consciousness Explained (Boston, MA: Little and Brown, 1991) 33.

[3]        Borrowed and adapted from Alvin Plantinga, ‘An Evolutionary Argument Against Naturalism’, Be Thinking Website, https://www.bethinking.org/atheism/an-evolutionary-argument-against-naturalism, accessed 20 November 2019.

[4]        Neil Postman, Technopoly: The Surrender of Culture to Technology (New York: Bloomsbury, 2007) 548.

[5]        Evgeny Morozov, The Net Delusion: The Dark Side of Internet Freedom (New York: PublicAffairs, 2011) 79.

[6]        Mary Midgley, ‘Against Humanism’, New Humanist, 25 October 2010 (http://rationalist.org.uk/2419/ against-humanism).