The word rational is widely misused. Scientists often apply it unnaturally, in ways that conflict with our biology. Nobel laureates Daniel Kahneman and Gary Becker, and their respective schools of thought, are on opposite sides of this breach with our nature. They revive an old struggle between prudent empiricism and blinkering “theorism” (an overreliance on idealized models).
...To minimize misuse, consider that the word rational really incorporates three types of assumptions: first, about desirable goals; second, about effective methods of attaining them; and third, about whether agents have the needed skills.
Ahaha, oh yes. One of the most tiring things about fellow atheists is the way they use those assumptions interchangeably, with the result that "rational" ends up, in practice, meaning little more than "anything I approve of and agree with". It's becoming one of those words that trigger an, uh, irrational anger in me. As Schopenhauer said about a term often used synonymously with rational:
On the other hand, the epithet reasonable has at all times been applied to the man who does not allow himself to be guided by intuitive impressions, but by thoughts and conceptions, and who therefore always sets to work logically after due reflection and forethought. Conduct of this sort is everywhere known as reasonable. Not that this by any means implies uprightness and love for one's fellows. On the contrary, it is quite possible to act in the most reasonable way, that is, according to conclusions scientifically deduced, and weighed with the nicest exactitude; and yet to follow the most selfish, unjust, and even iniquitons maxims. So that never before Kant did it occur to any one to identify just, virtuous, and noble conduct with reasonable; the two lines of behaviour have always been completely separated, and kept apart. The one depends on the kind of motivation; the other on the difference in fundamental principles. Only after Kant (because he taught that virtue has its source in Pure Reason) did the virtuous and the reasonable become one and the same thing, despite the usage of these words which all languages have adopted—a usage which is not fortuitous, but the work of universal, and therefore uniform, human judgment. "Reasonable" and "vicious" are terms that go very well together; indeed great, far-reaching crimes are only possible from their union.