If you wanted safety information on a used car, would it be wiser to trust the word of a used car salesperson or the findings of a consumer report? I hope that you would trust the consumer report over the salesperson because the salesperson has a vested interest in the quality of his products and an even larger one in getting you to accept his opinion on his products. The consumer report, on the other hand, would likely have no interest in advancing a one-sided view of any product. Similarly, if you wanted to obtain information on the historicity and veracity of Islam, would you ask an Islamic scholar who has been taught about Islamic sanctity since childhood, or would you ask a secular scholar with no emotional investment in Islam? Would you not also do the same for Hinduism, Mormonism, Buddhism, etc? If you utilize the same reasoning and choose the unbiased scholar in each instance, as you very well should, why make an exception only for Christianity? People who study a concept in which they have no emotional investment are going to offer more reliable conclusions than those who want the concept to yield a specific result. The decision in each case should be easy.
Scholars who began with no emotional investments in Christianity present the most unbiased conclusions on Christianity simply because they are more open during their studies to accept evidence that contradicts their tentative conclusions. Just as the used car salesperson will be hesitant to acknowledge and relay information that is damaging to the quality of his vehicles, the Christian scholar will be hesitant to acknowledge and relay information that is damaging to the veracity of his religion. We have no reason to think that belief in Christianity provides a special insight into the veracity of it because every religion can make a parallel claim. The opinions of individuals with ego involvement, emotional investments, or vested interests in the outcome of a debatable issue are less likely to change when confronted with new information because people have an innate inclination to seek only evidence that confirms their pre-established beliefs. We can describe this phenomenon, termed confirmation bias, as the tendency to seek out answers that will confirm our beliefs and ignore answers that will not. Research has long established the presence of this phenomenon in persuasive psychology.
According to Shermer, psychologists have discovered a process that people follow when given the task of selecting the right answer to a problem. Individuals (a) will immediately form a hypothesis and look only for examples to confirm it, (b) do not seek evidence to disprove the hypothesis, (c) are very slow to change the hypothesis even when it is obviously wrong, (d) adopt overly-simple hypotheses or strategies for solutions if the information is too complex, and (e) form hypotheses about coincidental relationships they observe if there is no true solution.[i] Moreover, by adopting these overly simple hypotheses and strategies for complex issues, we gain immediate gratification.
[i] Shermer 59.