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(intro music) I'm Ram Neta, professor of philosophy at the University of North Carolina, Chapel Hill, and I'm going to talk about rationality. Why be rational? If you're like most people, you think of yourself as a generally rational person. Although you sometimes make mistakes in your thinking or your planning, you tend to regard those mistakes as resulting from errors or gaps in the information that you receive from memory or testimony, rather than as resulting from your reasoning poorly from the information that you have. Also, if you're like most people, you think that other people are frequently guilty of poor reasoning and that your own reasoning skills are superior to theirs. But in fact, how good are you at reasoning? Try answering a couple of simple questions. First, supposed that Pat is looking at Chris and Chris is looking at Sam. Pat is married and Sam is unmarried. In this situation, is a married person looking at an unmarried person? 'Yes,' 'No,' or 'Not enough information to determine'? Most people answer 'C) Not enough information to determine,' because although they know that Pat is married and Sam is unmarried, they don't know whether Chris is married or unmarried. But a moment's reasoning will show that 'C' is the wrong answer. Even though we don't know whether Chris is married or unmarried, we know that Chris is either married or unmarried. Well, suppose Chris is married. Then, since Chris is looking at Sam, a married person is looking at an unmarried person. Now suppose that Chris is unmarried. Then, since Pat is looking at Chris, a married person is looking at an unmarried person. So, no matter whether Chris is married or unmarried, a married person is looking at an unmarried person. Let's try another question. Consider the number ten and the number 9.999... Are these two different numbers or two different names for the same number? Most people say they're two different numbers. But again, a moment's reasoning will show that they're just two different names for the same number. Let x equal 9.999... Then 10x will equal 99.999... And since x equals 9.999..., it follows that 9x is equal to 90. Dividing both sides of this equation by nine, it follows that x equals 10. But since x equals 9.999..., it follows that 10 equals 9.999... The two questions I've just chosen illustrate a general pattern: most people, even highly intelligent and well-educated people, do not exert even the small effort required in order to reason well. This is true not merely when it comes to purely theoretical questions, like the ones I've asked above. It's also true when it comes to practically consequential questions, like how to invest our resources or which consumption decisions to make. For example, investors frequently acquire irrationally inflated expectations about the future growth of some asset, thereby creating a speculative bubble in the value of that asset. Once investors begin to realize that the asset's growth can't satisfy these irrational expectations, they respond with an equally irrational fear, and consequently, the asset suffers a very rapid sell-off and rapid decline in value. The disastrous personal and social consequences of these booms and busts are by now well-known. So, other people's unfavorable views of our own rationality tend to be more accurate than our own favorable view of it. Human beings are, to a larger extent than we care to admit, irrational animals and our species has paid dearly for such irrationality. But there are two ways of addressing the problems created by human irrationality We could address them by trying to improve human rationality, or by trying to design systems that accommodate for the predictable effects of human irrationality. In his popular book Predictably Irrational, Professor Daniel Ariely proposes ways of doing the latter. This focus on designing systems to accommodate human irrationality is understandable, since, thanks to the research of Ariely and others, we now know much more about how to predict human irrationality, and so how to design regulations and institutions that can operate to avoid its otherwise adverse effects. In contrast, we still know very little about how to improve human rationality. But if we can design regulations and institutions that can operate to save us from the adverse consequences of our irrationality, then is there any reason to improve our rationality? Is rationality something still to be valued, even once we know how to avoid the harms that would normally result from its absence? Presocial humans would have died very quickly if they did not have formidable physical strength and speed. But we no longer think that a person's lack of such strength and speed is a personal failing, since we now have tools and vehicles that allow the weakest and slowest among us to do more and live longer and more comfortably than presocial humans could ever have imagined. If we develop the social technologies to correct for the adverse consequences of human irrationality, then should we continue to think of irrationality is a personal failing? Should we continue to value and to try to cultivate rationality in ourselves and in others? If so, then why? Subtitles by the Amara.org community