We value having true beliefs, and the way we support the thought that we have true beliefs, and our opponents don’t, is by giving reasons for our beliefs. But what if, in the process of giving reasons, we’re really just rationalizing — cherry-picking the arguments and evidence that we like, and unfairly dismissing the arguments and evidence we don’t like?  

Hilary Kornblith has an interesting paper discussing this issue: “Distrusting Reason”, from Midwest Studies in Philosophy 1999. He writes:

When we rationalize, at least when we do it sincerely, we are not aware of doing so; we are not aware of being motivated by anything other than a desire to get at the truth. And it is precisely because of this that the process of scrutinizing our reasons for belief may, at times, be terribly counterproductive from an epistemological point of view. Scrutinizing our reasons, when we are engaged in sincere rationalizing, will get in the way of the goal of believing truths.

How does giving reasons get in the way of the goal of believing truths? Giving reasons can do so because  (according to Kornblith) we give a biased presentation of the reasons:

When we scrutinize our own reasons for belief, we … take the evidence that is available to us at face value. Because the biasing processes that selectively filter our evidence take place behind the scenes, as it were, unavailable to introspection, we are able to produce perfectly good reasons for belief, reasons that not only survive our private scrutiny, but would survive public scrutiny as well. The process of scrutinizing our reasons, in the case of sincere rationalization, gives the illusion of being responsive to available evidence. And the more intelligent one is and the better one is at the skills of presenting and defending arguments, the more powerful the illusion will be, if one engages in rationalizing, that one is forming beliefs in ways that are appropriately responsive to evidence. … From the point of view of belief fixation, reason-giving is frequently epiphenomenal. 

I’m inclined to think that Kornblith is right that this sort of rationalization at least sometimes happens. 

It’s worth thinking about for what topics of belief one would be most likely to rationalize. I can most easily see this happening for deep-seated beliefs, beliefs that impact, for example, the way one views one’s purpose and meaning in life. Thus, beliefs about the existence of God are prime candidates for rationalization. When people give arguments for why they believe, or don’t believe, in God, we should be wary of the possibility that they are giving a biased presentation of the arguments. Perhaps even more importantly, the people who are giving the arguments should be wary of the possibility that they themselves are evincing bias. I get the sense that people are pretty good at remembering to search for bias when they hear arguments for views they oppose, but are remarkably non-self-introspective when it comes to their own presentations of reasons for belief.