What does it mean to be rational/reasonable? Is it reasonable to believe only things that can be and are verified empirically? Are things reasonable only if we understand them at an intuitive level?

Is it reasonable to believe in God? An atheist would say it is not because there is no compelling evidence for that. A theist would say yes; how else would we explain the complexity that we see. Here the evolutionary biologist would say that evolution explains it - but this would not be sufficient for many theists. This is somehow understandable because we cannot really grasp what a billion or a million years, not even a thousand years; we cannot experience time periods that long - so we cannot really see how the small changes lead eventually to so vast outcomes.

Is it reasonable that electrons* exist in a superposition of states before measurement? A physicist would say that it doesn't matter; this is the way nature works. But is it reasonable from a philosophical point of view?

*Or any other quantum particle

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    You may find this interesting if you are interested in physics. Heisenberg marxists.org/reference/subject/philosophy/works/ge/heisenb5.htm – Gordon Aug 13 '18 at 16:15
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    I think at some point he might have added a chapter on religious belief, so you may want to check the library for a revised edition. amazon.com/Physics-Philosophy-Revolution-Modern-Science/dp/… He was a German who was part of a certain era, nevertheless he was very educated in philosophy; he took it seriously. – Gordon Aug 13 '18 at 16:21
  • Broad questions of this sort are not suitable for this site. Please read online encyclopedias, like Wikipedia's Rationality, and narrow the scope down to something more specific. – Conifold Aug 14 '18 at 0:20
  • As an extreme defintiion, Rational Choice Theory describes a "rational" actor as one which is goal seeking, and self-observing, meaning it sees how it affects the world around it, and tries to adapt to better seek its goals. – Cort Ammon Aug 14 '18 at 6:09

In economics, rationality is relatively more associated with choices made than with beliefs held. The focus is primarily on maximizing expected utility, justified in part by the expected utility theorem. But beliefs are also considered, and in this context it is often held that rational beings would perform Bayesian inference. This still leaves a lot of flexibility in terms of what someone considers to be the prior distribution. For example, someone might argue that he or she has such a large prior belief in the existence of a specific deity that the evidence is not enough to overwhelm this prior belief. Ruling out such an argument would presumably require a different theory, or at least it's not entirely clear how one might argue against certain prior distributions.

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