The philosopher fears, "It is hardly likely that our cognitive faculties and our thinking ability are any good for helping us form beliefs if blind forces, that don't know what they are doing, have given rise to them".
He may argue, "God has made us to discern and find truth and God is honest." But that does not help for he just said there is no grounds for trusting how and what we think.
God is degraded like some kind of crutch. Worshipping a crutch is incoherent.
CS Lewis tended to suggest that if our thoughts ultimately have purely physical causes, they were therefore irrational. Lewis follows an out-of-date philosophy of mind. Beliefs and actions and reactions all go together. Lewis argues that if our reason is the product of chance it is no use so it can lead you doing strange things. For example, you might boil water in an empty pot. Or you might try to light a fire with ice. Our experience shows that he is wrong. He is stressing theory over reality.
Elizabeth Anscombe pointed out that many causes of our beliefs could be non‑rational (e.g., neurons firing) without being irrational in the sense of logically incorrect. She stressed that the terms “cause,” “reason,” and “explanation” have multiple senses. Anscombe argued the ambiguity in Lewis’s language undermined his argument — just because a belief arises from natural processes doesn’t mean the reasons for that belief are invalid or that reason itself collapses.
If there are reasons to distrust reason, it follows that it cannot be always wrong. Nobody argues that a liar must be disbelieved all the time.
We all have doubts about the validity of reason for we are imperfect. We have difficulties with it too. Difficulties are not doubts but put you at risk of developing doubts. Difficulties about reason itself are different from difficulties about the truth and facts. An analogy is when Catholics say they may have difficulties about matters of faith, but that a thousand difficulties do not add up to one doubt.
God is optional for reasoning: believing in God doesn’t increase the reliability of your thought processes; it may guide some people morally or spiritually, but reason itself doesn’t require it.
Reason is like a sense: sight and hearing evolved to help us navigate the world. Reason evolved to help us navigate truth. It doesn’t need a divine supervisor to work; it needs feedback from reality. Better to enjoy the reason we have, even if we have doubts about it, than to destroy it totally with using God to ground it.
Faith as a mental habit: faith can be compatible with reason, but it’s not a prerequisite. You can reason about the world, ethics, and knowledge without invoking a deity.
Evolution ensures our reasoning isn’t completely broken. We can trust it enough to test reality, learn, and adapt.
LOVE GOD WITH ALL YOUR MIND?
Page 5 of Mere Theology by Alister McGrath says that as the word of God in the Bible commands us to love God with all our minds that we are being asked to think about God. McGrath says that loving God and wanting to understand him better go together. McGrath also says that we cannot let Christ - and by implication God - rule over our hearts unless we let him guide us in our thinking. He says the command shows that Christianity is not against the use of the intellect and not against free inquiry to check the religion out for veracity and correctness.
The point of the commandment is that we are to let God do the thinking for us. It says nothing about thinking for ourselves. Indeed, in those days there was no science. The command was given to the Jews - this faith was an umbrella for many different Judaisms. They couldn't even agree if there was a life after death. The people didn't have the means or the time to think. They had only short lives as well. The thinking people could do for themselves had to be very limited because of the times they were in. To read the commandment as saying we can think for ourselves as long as we let God enlighten us is anachronistic. Those people did not have much time for the notion of a God putting thoughts in their minds.
And if you use your head and get stuck and God has to fill in the blanks then why will your filled blanks differ from the next person? No two religious people agree on everything and there are fundamental differences between many of them. If God puts thoughts in your mind that is not you thinking for yourself but you not thinking for yourself. In reality what Christianity has is letting you think a bit and that is all.
EXPERIENCE AS GROUNDING OF REASON
"I have a spiritual experience of God. God lovingly has given me free will and reason. I can trust them for I can trust this loving God whom I experience." Others may say that they have that experience too. But the fact remains that the experience is your experience and nobody else's. Many feel they have an experience of the absence as in non-existence of God. Using the scientific method to justify beliefs is better than resting on experience. Anybody can verify the scientific method. Science may have errors but it is better to start with doubt and us the scientific method to get out of it than to depend on anything else such as a religious or spiritual experience. With those you repudiate the reality check. So you end up diluting reason not serving it. You stop yourself trusting it properly.
If an experience of God is so great that it can support reason, why not just sense that reason supports itself? Why not have an experience of the power of reason? By bringing God in to justify reason you are doing that anyway but in a roundabout awkward and confused way. Why not just do it and leave God out?
Reason itself says that even if the mind is just thrown together by blind forces, that in itself does not prove it has no capacity to discern truth. In theory a calculator can be made by chance and give 1 + 1 = 2. You do not need that mystical foundation.
A FOOLISH ARGUMENT
Some strangely argue that if you reason that there is a God, then you fall into idolatry. They allege that you end up worshipping a product of your logic and not God. This is untrue. The idea that God gives us reason as a gift refutes it. If God uses reason as a tool to bring you to him then it is not idolatry. You are not worshipping how you think but somebody who your reason tells you is there. Even if this were idolatry, it is still better than worshipping anything you have little or no evidence for and something you apply no logic to.