C.S. Lewis on atheist thinking

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Supposing there was no intelligence behind the universe, no creative mind. In that case, nobody designed my brain for the purpose of thinking. It is merely that when the atoms inside my skull happen, for physical or chemical reasons, to arrange themselves in a certain way, this gives me, as a by-product, the sensation I call thought. But, if so, how can I trust my own thinking to be true? It’s like upsetting a milk jug and hoping that the way it splashes itself will give you a map of London. But if I can’t trust my own thinking, of course I can’t trust the arguments leading to Atheism, and therefore have no reason to be an Atheist, or anything else. Unless I believe in God, I cannot believe in thought: so I can never use thought to disbelieve in God.

C.S. Lewis

[Emphasis mine]
This quote from noted theologian C.S. Lewis highlights a major problem for modern atheists: they borrow heavily from a worldview they reject. When thinking about the process of thinking, atheists assume that their brains can be relied upon to give good answers. In a universe of philosophical materialism (the idea that the physical is all that exists), there’s no good reason to assume that our brains are trustworthy in that way. In fact, Darwinian evolution would suggest otherwise, because our brains are then the result of many random mutations and natural selection. In other words, our brains contribute to the survival and spread of our genetic information…and everything else is “gravy”. Any other function our brains might perform could be eliminated after another mutation.

If our brains are simply biochemical and not the creation of some greater mind; if our brains are not connected to an immaterial mind; if the physical is all that truly exists, we can’t trust in reason to get us anything but grandchildren. The only way to speak meaningfully about reliable ideas is to presuppose that our brains function as something more than a blob of DNA-spreading goo.