In an 1839 letter from Emma to Charles Darwin, shortly after they were married, she wrote about her worries that Charles’ pursuit of scientific questions on evolution might lead him further away from religious faith. Emma wrote: 

“May not the habit in scientific pursuits of believing nothing till it is proved, influence your mind too much in other things which cannot be proved in the same way, & which if true are likely to be above our comprehension.”

At the time, Darwin would have been around 30 years old, two decades before On the Origin of Species was published. Their correspondence showed that Emma’s concern that Charles’ need for evidence could not be applied to matters of faith, and that this probably meant — to her distress — that they would probably be separated in the afterlife. At the bottom of her letter, Charles added his own note: 

“When I am dead, know
that many times, I
have kissed & cryed
over this. C. D.”

It seems clear that Charles had his own internal struggle over science, faith, and possibly being thought a fool or even ostracized for his ideas. It is also very difficult to be agnostic about everything until all of the evidence is in. We often make shortcuts, accepting the folk-wisdom passed down to us over the generations, or reaching into our own personal experiences (however unrepresentative they may be) to arrive at some conclusion. This is probably necessary — who has time to wait decades to settle a scientific question, or any question?

Ultimately, the advantage of a scientific approach is that it is supposed to circumvent our (often self-serving) biases, to arrive at truth, or at least some tentative conclusion based on the best evidence available. This is a tall order to ask, however. Letting go of ego is not an easy thing to do and very often, we would rather have our biases confirmed rather than challenged. We like to be right, even if experience often shows that we are not.

Related 

Darwin, Oversimplified