"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 certain physical or chemical reasons to arrange themselves in a certain way, that gives me, as a by-product, the sensation I call thought. But if it is so, how can I trust my own thinking to be true? It's like upsetting a milk jug and hoping that the way the splash arranges 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 can't believe in thought; so I can never use thought to disbelieve in God." C.S. Lewis, The Case for Christianity"
Let's examine C.S. Lewis's above comments, and see what a miserable wreck of tortured logical fallacies, it is.
Of course, this is a common fallacious argument, known as "Denying the antecedent". Lewis essentially implies that the only alternative to the notion that our brains were designed by a creative, intelligent God is that our brains are just a random collection of matter. He denies or ignores any other possibility. Of course, his argument doesn't work, because in the world of science, (you know, the REAL WORLD) nothing is simply "random chance", especially when we talk of biological matters. In science, everything happens as a matter of cause and effect.
Lewis then tries to explain what many people who never bother to read any science texts, or get their facts straightened out before trying to explain science to others do. He completely makes up how science allegedly explains the workings of the brain. Scientists, from Neurophysiologists, to biologists, to those who specialize in evolution, do not describe any biological processes as random, nor would they explain the workings of the brain in the simplistic way that Lewis does. Like many of the Christians who try to make arguments against established science, Lewis is putting his money in the ignorance of believers, or at least he is as ignorant as people who think that he gave an accurate explanation of how science describes brain functions.
He then says something so astonishingly irrational and logically fallacious that it's hard to believe that someone of his apparent intelligence and stature would make such a conclusion. He claims that "Unless I believe in God, I can't believe in thought..." Yes, apparently, belief in thought is dependant on one believing on God. We apparently are supposed to just take his word for it. After all, he's C.S. Lewis, author of the Narnia stories. Being famous and popular gives him the authority to be right about whatever subject he writes about! Next thing you know, these Christians will tell us that we can't piss unless we believe in God, first.
Lewis states that we cannot trust our thoughts, UNLESS we believe in God. Apaprently, Lewis never got wind of concepts like objectivity, logical thinking, and rationality. of course, Lewis doesn't define what thought is. After all, he may be playing the word-redefinition game, and using his own personalized definition of thought, which he assumes is the same definition that everyone else uses. Of course, Lewis did not have access to information on Neurophysiology before 1963, because the field is highly specialized, highly technical, and prior his death in 1963, there was no actual field of Neuroscience, or international organizations of scientists to get information from, and of couse, no internet. So in this sense, we can't really blame Lewis, because he died before neuroscience was an accessible topic for most people.
Thought, by definition, is simply a process that brains perform. At it's basis is the interaction of neurons, and the sending of signals from sensory organs. "Thought" is what happens when the neurons in the brain are stimulated and various parts of the brain process that information. I doubt that Mr. Lewis was even aware of the concept of thought as a biological function when he wrote his oft-quoted comment. But it is very well documented what thought is, and even as early as Ancient Greece, philosophers at least understood that thinking was an action, and they even offered prescribed methods for performing it, which we call the principles of logic. Even an Oxford grad like Lewis should have been familiar with that information, because the classic Greek philosophers are part of the standard curriculum there.
In the real world, to validate thoughts, we compare them to data that we receive from our senses. It is reasonable to say that when you can measure and record data, and several independant people set forth to measure and record the same data, comparing each others' data is a reliable way of determining the validity of it.
The difference between rational thinkers and the irrational religious people who push C.S. Lewis's outdated and uninformed philosophy, is that the irrationally religious never seem to be open to the possibility that they might be wrong about anything; everything they think is truth. Their faith is used as a way of validating their own thoughts, however erroneous they may be. Rational people do not innately trust thoughts. They know that their opinions and perceptions are not neccesarily the truth, and the use the tools of research, logic, and rational thinking to determine which thoughts are valid and which are not.
Many religions, Fundamentalist Christianity included, are nothing more than thought systems that let lazy people proclaim themselves to be wise and informed on any topic, without actually going through all that annoying work of reading, researching, comparing data, and actually learning anything about it. This is why we get loads of uneducated, non-science-trained, non-scientists confidently telling educated, degreed, seasoned, professional scientists that everything they know is wrong. This religious mindset lets these people be self-proclaimed experts on anything, and they never feel the need to verify any of the facts that they seem to make up on the fly.