Continuing my thoughts based on the comments on
this post:
* It seems that being rational helps us achieve our goals and needs, and actually puts an individual at an advantage, in contrast to morality, which apparently puts an individual at a disadvantage. So one might say to 'Why be rational?': 'Because it is good for us.' /'Because it works for us.'
* While morality apparently puts an individual at a disadvantage, it is advantageous to the society as a whole. A society in which individuals act morally is more likely to flourish and survive. Therefore, in answer to this question 'Why be moral?' an individual may have no answer, a society can definitely answer 'Because it is good for us.' / 'Because it works for us.' And if a society is moral, then indirectly, the individual would be forced to be moral.
* While rationality help us in practical matters, it is not always advantageous to the individual. Consider the example of an individual using rationality to discredit a religion in a society that is very strongly religious, and is condemned to be burned on the stake on the charge of apostasy. In this case, rationality is leading that individual to a painful death. And yet, there is something worthwhile and noble about this pursuit of 'truth' even when this puts you at a disadvantage. Very few individuals would actually be rational to this extent, and yet, I presume, most would see this act of sticking-to-rationality-in-the-face-of-death as something admirable. It wouldn't make sense unless some part of us believes that there is an inherent value in rationality, in 'truth'.
* I have suggested that rationality even in the absence of its utility is viewed as a worthwhile goal for its own sake. Morality, it seems, has much less utility for an individual, but even so, it is viewed as (/ought to be viewed as) a worthwhile goal for its own sake. That is where I believe the analogy lies.
* This is not a real philosophical answer to the questions that I had posited. It is just an evasion. What I say turns out to be something like this:
"Why be rational and moral?"
"Because they are worthwhile pursuits having inherent value."
"And why do they have inherent value?"
"Because this is what our intuitions tell us /Because that's what humans are programmed to believe."