Does doubt have a cognitive function, i.e., is it useful in certain circumstances?
It seems obvious that it does – otherwise, why would organisms such as ourselves be capable of experiencing the emotion of doubt? One purpose of doubt seems to be to get the organism to check whether what it took to be true is true.
(It also seems obvious that doubt can be misplaced, like pretty much any other emotion – a person might simply have a nervous habit of thought, or consistently underestimate their own abilities, and so on.)
For example, I’m walking along a path, and am supposed to arrive in a certain amount of time. After that amount of time comes and goes, without yet arriving, I might start feeling doubt about whether I’m on the right path. The doubt is a call to attention or action – to get the organism to check whether it should modify its beliefs given new data.
What is the appropriate response? Look at the new data, and consider modifying one’s beliefs. Then get back to action, now with a better picture of the relevant data.
Whenever doubt arises in this way, one must look at how to fit the new data into the array of theories one might be able to have, and which theory one should pick given the new data. It’s about theory choice, in other words. This is much discussed in philosophy of science, but is constantly happening in other parts of our lives. In the broad outlines, there isn’t much that is unique about science in terms of theory choice – except that the consequences usually aren’t as immediately practical.
In theological literature, much attention is paid to doubt in ‘God’. Doubt here is no different than doubt in other propositions. That is, some new data has come in, which bears on some belief and so prompts the organism to consider it and revise or discard beliefs as is most warranted. I.e., what is the most reasonable conclusion given this new picture of the data?
Doubt in God usually comes about from the problem of evil. I.e., something bad happens in one’s own life, which can prompt serious reconsideration of whether there is a good God. How do Christians explain this sort of data? Usually by recontextualizing the data – God thinks about the whole, and this thing is just a part. If one stays in a strong relationship with God, then later one will see how this part fits into the whole. What grounds does the Christian have for believing such a thing? Because they can look back in the past and see where things that were bad that happened to them ended up leading to good. For example, a business didn’t work out, but the lessons learned in that business then led to business success after that.
The point is that doubt, in its proper place, is useful – it is a stimulus which can lead to a better picture of just how the universe works. I don’t think the appropriate response, in terms of Christianity, science, or what have you, is to shrink from a legitimate stimulus – to run away from it. Central to Christianity is the notion of ‘restoration plus’ or ‘resurrection’ – of not avoiding things but going through them, and coming out the other side transformed (and, hopefully, for the better). The stimulus of doubt is like the call to action in the archetypal ‘hero’s journey’.