Is it possible to have a reasonable belief while still acknowledging that you could possibly be wrong? Yes, clearly. In fact, the hallmark of being reasonable would be readily acknowledging claims you could be mistaken about and figuring out why. But many people are confused about this issue. They artificially elevate the standard of reasonableness on the atheist, insisting that you can’t prove a negative, or that “you could be wrong” so the atheist’s confidence that there is no God is unwarranted, and so on. Being an atheist is not justified, it is argued, because there might turn out to be a God, but the same possibility of being wrong somehow isn’t a liability for believing. In fact, with belief in God leaping to a conclusion that is unwarranted by the evidence or believing by faith is often praised as somehow virtuous. Furthermore, when challenges to the reasonableness of theism arise, many believers are content to embrace possibilities as justification. The fact that there could possibly be a God who possibly has a plan whereby all of the suffering in the universe actually serves some indispensible greater good is enough for many to conclude that their belief has been vindicated as reasonable or at least epistemically inculpable. The double standard seems to be that the atheist, in order to be reasonable, must achieve absolute certainty. Until then, she has adopted a degree of confidence in believing that there is no God that cannot be warranted by the evidence before us. But the believer is at liberty to construct the wildest, fantastic schemes on mere possibilities, and as long as long as it appears possible that there is a God that fits this scheme, then believing is epistemically permissible. We are remarkably indulgent with the standards of evidence when it comes to religious believing, but inconsistently strict when it comes to irreligious believing.
The general point is that all of us have countless reasonable, justified beliefs that have been proven to our satisfaction, but that don’t meet the “absolute certainty” test. If absolute certainty is required for justification, then almost none of the beliefs we have are epistemically acceptable. Are you absolutely certain that your husband or wife is not an android?
Every reasonable person has to deal with some degree of uncertainty about every one of their beliefs. The possibility that you could be mistaken when you take something to be true, by itself, doesn’t render that belief unreasonable. Consider members of a jury who have to decide a defendant’s guilt or innocence. Even when the case for the defendant’s guilt is ideal, a thoughtful juror would acknowledge that they might be mistaken. But the reasonable thing to do is still to draw a conclusion. Possibilities, as I have argued before, are not probabilities. It is possible that there really is a Tooth Fairy, an Easter Bunny, and that Santa really does live at the North Pole. But those possibilities don’t make believing that there is no Santa unreasonable.
So it is perfectly consistent to consider the evidence, draw what you take to be the reasonable conclusion and be sure you are right while acknowledging that you could be mistaken or that new information could lead you to change your mind. How could we find the atheist whose view has these features epistemically culpable or guilty of some gross irrationality?