Although we don't typically use the term, we speak of rationality and irrationality all the time.

"What you did makes no sense!"
"This guy is a real nutcase..."
"What on Earth was she thinking?"
"Why some people are idiots?!?!" ()

These are attributions of irrationality. Rationality can refer to actions or beliefs. The term has a special meaning in economic and decision theory, but the general question that I want to pursue in this thread is what most of us generally mean when we say or imply that someone is being irrational. I'm going to pose some additional discussion questions below and I'll follow those up with some of my own conjecture. Also, for this discussion beliefs (true-or-false statements about the world) should be distinguished from values (moral right-or-wrong statements about the world) and attitudes (like-or-dislike statements about the world).

  • Do humans generally think and behave rationally or irrationally? If it's somewhere in between, when are we rational and when are we irrational?
  • What is the role of emotions in rationality? Does emotion help or hinder us in achieving rationality? Or is the question of emotions irrelevant?
  • Is it rational or irrational to value events that happen in the present more than those same events if they were to occur in the future? In other words, to what extent should we rationally be concerned about the welfare of our future selves relative to our present selves?
  • Is logical consistency a necessary condition for rationality? Is it a sufficient condition?
  • Is is necessary for our beliefs about the world to correspond with objective reality? (Assuming that it is possible for us to know objective reality... let's save that discussion for another day.)
  • Referring to the earlier distinction between beliefs, values, and attitudes: can values and/or attitudes be irrational?
  • If a certain act or belief ultimately benefits a person, is that alone sufficient to call that act or belief rational? Or is it necessary for the chosen act or belief to be the best possible for the actor in terms of expected value? In other words, if there are two choices A and B, and A has the higher expected value according to the judge's personal knowledge, but in fact B will ultimately benefit the judge more if chosen, which is the more rational choice?
  • Are the tenets of rationality universal or are they culturally and historically relative?
  • Does it matter whether people are strictly rational or not? How hard should we work to make our beliefs and decisions conform with rationality?

I think that what I mean when I speak of rationality is a combination of (a) personal consistency among beliefs, values, and attitudes, and (b) personal consistency between beliefs and behavior. (a) defines rational beliefs while (b) defines rational behavior.

Let me try to explicate (a) in a precise way. For a set of beliefs to be rational, it should not be possible to combine any two of those beliefs in a syllogistic way and have their logical conclusion conflict with another belief. For example, let's say that I believe that the Earth is over 4 billion years old. However, let's also say that I believe the Bible says that the Earth is a few thousand years old, and that I believe that everything written in the Bible is true. Since it follows from these two that I must believe the Earth to be a few thousand years old, but this conflicts with my earlier belief that the Earth is over 4 billion years old, this is an irrational set of beliefs. In order to make the beliefs rational, I can either discard my belief that the Earth is over 4 billion years old or discard my belief that everything written in the Bible is true. Importantly, these are equally valid ways to achieve rationality, ignoring all other beliefs.

I think that values and attitudes are subject to rationality. That is, values and attitudes can be considered irrational if they conflict with each other or a set of beliefs. Let's say that I view abortion as being morally wrong. Let's also say that I think something is wrong if it harms a potentially conscious, living thing against its will (a value), that I think life begins at conception (a belief), and that consciousness begins some time around birth (a belief). It follows that I must believe early fetuses to be living but not capable of consciousness, and since I value consciousness as required for moral consideration, I must not view abortion as wrong. But this conflicts with the initial value, so the set is irrational.

I don't think that it's necessary for one's beliefs about the world to correspond with objective reality in order to be considered rational. However, I think that in almost all cases a personally coherent set of beliefs will result in one which happens to correspond with objective reality. For example, if I believe that there is no global warming, but the majority of respected scientists tell me that there is global warming, and I believe that scientific consensuses are usually correct, then I am likely to revise my initial belief and begin believing in global warming. (Which I would argue is in line with objective reality.)

(b), which concerns behavior, can be unpacked in a similar way. If I smoke cigarettes, but I value my health and believe that cigarettes harm my health, then it is irrational for me to smoke cigarettes. To become rational I can stop smoking, discard my belief that cigarette smoke is harmful, or stop valuing my health.

To tackle a few more of the discussion questions, I think that these tenets of rationality are universal rather than culturally/historically relative, that beliefs and behaviors that happen to be beneficial are still irrational if they violate these tenets, that people are generally rational but are irrational often enough to give us pause, and that it is important that we strive to be rational. I can try to expand on these points if you like but for now I'd like to stop blabbing and open up the discussion. What are your views on rationality, and what do you think about mine?