Jim Holt’s sober review of Daniel Kahneman’s new book (Thinking, Fast and Slow — By Daniel Kahneman — Book Review – NYTimes.com) is wisely cautionary. An excerpt:
“Even if we could rid ourselves of the biases and illusions identified in this book — and Kahneman, citing his own lack of progress in overcoming them, doubts that we can — it is by no means clear that this would make our lives go better. And that raises a fundamental question: What is the point of rationality? We are, after all, Darwinian survivors. Our everyday reasoning abilities have evolved to cope efficiently with a complex and dynamic environment. They are thus likely to be adaptive in this environment, even if they can be tripped up in the psychologist’s somewhat artificial experiments. Where do the norms of rationality come from, if they are not an idealization of the way humans actually reason in their ordinary lives? As a species, we can no more be pervasively biased in our judgments than we can be pervasively ungrammatical in our use of language — or so critics of research like Kahneman and Tversky’s contend.”
Holt’s question is the right one to ask; ‘rationality’ presumably enables those possessing it to do something, and each rational creature does whatever the amount of rationality she possesses enables her to do, no more and no less. The urge is almost irrepressible to charge ‘nature’ with making us insufficiently rational. But insufficient for what? Without an answer to that question, of course, the charge is an empty one. But the charge is in any case ridiculous: it assumes nature can be held to account, that it can make mistakes like giving rise to systematically irrational creatures. And wouldn’t it be welcome solace if nature’s irrational progeny were bright enough to know where to cast the blame?
We endanger any useful understanding of ‘rational’ and ‘irrational’ if we persist in thinking that ‘irrational’ is something that we are or can be. Irrationality is more profitably understood as a dismissal of a process of thinking that cannot currently be endorsed; to fix any belief is necessarily to reject many others and often the sequence of beliefs that brought it about. Any belief we currently endorse is, by our own lights, ‘true’, and the sequence of beliefs and inferences on which it rests, ‘rational’. All those beliefs and sequences we acknowledge to be necessarily excluded are deemed ‘false’ and ‘irrational,’ respectively. Irrationality (and, mutatis mutandis, falsity) is the necessary by-product of the acknowledged incompatibility of two (or more) distinct run-ups to a new belief.
Rationality is likely nothing more than the ability to think about thinking, and irrationality as the warning label for any kind of thinking one recognizes as incompatible with one’s own current performance (we can dismiss our past thinking as irrational, but not the present product; puncturing today’s pretensions to superior thinking must wait for tomorrow’s new and improved version). If nature made us systematically irrational, it is because it made us rational. The former is not the privation or dysfunction of the latter; rather they are two inseparable, close to indistinguishable, sides of the very same ability. Irrationality is the reflection rationality glimpses in the mirror: quite understandable, perhaps, but not quite right.