As Eliezer and many others on Less Wrong have said, the way the human species rose to dominate the Earth was through our intelligence- and not through our muscle power, biochemical weapons, or superior resistance to environmental hazards. Given our overwhelming power over other species, and the fact that many former top predators are now extinct or endangered, we should readily accept that general intelligence is a game-changing power on the species level.
Similarly, one of the key ingredients in the birth of the modern era was the discovery of science, and its counterpart, the discovery of the art of Traditional Rationality. Armed with these, the nations of Western Europe managed to dominate the entire rest of the world, even though, when they began their explorations in the 15th century, the Chinese were more advanced in many respects. Given how Western Europe, and the cultures derived from it, has so completely surpassed the rest of the world in terms of wealth and military might, we should readily accept that science and rationality is a game-changing power on the civilization level.
However, neither of these imply that intelligence, science, and rationality, as a practical matter, are the best way to get things done by individual people operating in the year 2009. We can easily see that many things which work on the species level, or the civilization level, do not work for individuals and small groups. For instance, until the discovery of nuclear weapons, armed conflict was often a primary means of settling disputes between nation-states. However, if you tried to settle your dispute with your neighbor, or your company's dispute with its competitor, using armed force, it would achieve nothing except getting you thrown in prison.
People are crazy and the world is mad, but it does not necessarily follow that we should try to solve our own problems primarily by becoming more sane. Plenty of people achieve many of their goals despite being completely nuts. Adolf Hitler, for example, achieved a large fraction of his (extremely ambitious!) goals, despite having numerous beliefs that most of us would recognize as making no sense whatsoever.
We know, as a matter of historical fact, that Adolf Hitler and his Nazi Party, despite being generally incompetent, unintelligent, irrational, superstitious and just plain insane, managed to take over a country of tens of millions of people from nothing, in the span of fifteen years. So far as I am aware, no group of people has managed to achieve anything even remotely similar using, not only rationality, but any skill involving deliberative thought, as opposed to skills such as yelling at huge crowds of people. However, it is a corollary to the statement that no one knows what science doesn't know that no one knows what history doesn't know, so it is entirely possible, perhaps likely, that there is something I am overlooking. To anyone who would assert that intelligence, science or rationality is the Ultimate Power, not just on the level of a species or civilization, but on the level of an individual or small group, let them show that their belief is based in reality.
My other comments in this thread seem to have misread Tom's intention, so let me try again. I'll summarize what I think the point is, so if I'm off, it'll be obvious.
The point is that, while rationality has been important and effective on the level of Western civilization, it isn't really a super power when it comes down to individual behaviour. Thus, claims about rationality being all-important are dramatically overstated; there are much more important criteria for success.
My criticism of this, and the reason that I think it's generating debate the way it is, is that the first half is simply false, and the second half is so obvious that people refuse to interpret it correctly.
Western civilization isn't particularly powered by rationality. There's a pretty complex cultural and institutional framework that powers the West and its prior success, some of which is thoroughly irrational (Mercantilism, anyone?). Rationality may have played some role in the West's rise to dominance - it certainly did in a technological context - but you don't need to be rational to point guns at people, even if you do need to be rational to invent guns.
Conversely, at the individual, rationality is easily outweighed by other factors. If you want to be a baseball player, hand-eye coordination, speed, and strength top rationality. For a politician, pick charisma. For a designer, pick social skills and taste. For a scientist, if you have basic competence in your field, pick skills conducive to publicity and obtaining grants. The only special thing about rationality is that, insofar as all of these professions must make decisions, additional rationality will help all of them, whereas running faster will not help most politicians.
There's also an issue of survivorship bias. There are a whole lot of very irrational people. Therefore, saying, "Being irrational isn't so bad; look at so-and-so, he did pretty well," is actually not a useful argument. I guarantee you that, if your goal is being a lottery winner, being less rational will serve you extremely well. If a million irrational people all set out to be movie stars, ten succeed, and the rest are miserable, this does not make irrationality a good strategy.
See http://lesswrong.com/lw/1ko/on_the_power_of_intelligence_and_rationality/1d5t