There is a saying that the work of ordinary geniuses can be reproduced while the work of exceptional geniuses--magicians--is so dazzling that you can't imagine doing it. Scott calls people who popularize science to their generations "prophets." Scott is a prophet and a magician and this is why he lands on the page of the smartest living people. see more on Scott Aaronson
Political commentator, Keynesian economist, popular pundit, Paul Krugman extracts simplicity from confusion and distills it to a wide audience in terms everyone can understand. Paul Krugman earns his way onto this list of the smartest people alive.
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Political scientist, intellectual renegade, honest as stone, Norman Finkelstein will not be cowed. He earns a spot on this list of the smartest living people.
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A cognitive scientist, philosopher and linguist, Steven Pinker has perhaps done more to move these important social sciences into the fold of the hard sciences than any of his peers. While not infallible, he is an exacting, insightful thinker, and for this reason he earns a spot on my list of the smartest people alive.
#706 on The Greatest Minds of All Timesee more on Steven Pinker
Ed Witten almost became an economist. Thank god he didn't, because physics and mathematics wouldn't be the same without him. With a Feynmanesque explanatory ability and a Penrosian mathematical prowess, this scientist takes names and kicks butt. He fits snugly on my list of the smartest people alive.
#548 on The Greatest Minds of All Timesee more on Edward Witten
The irascible Murray Gell-Mann knows so much about so many things that it's hard to exclude him from this list, even if his legendary cantankerousness is not an admirable intellectual trait. Fundamental physics wouldn't be the same without him, and this list of the smartest living people wouldn't either.
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Glenn Greenwald writes prodigiously on politics and rarely, if ever, does he err. He is one of a kind and sits not at all awkwardly on a list of the smartest people alive.
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Noam Chomsky may get some things wrong occasionally, but so does everyone else. He is usually correct, almost always insightful, and his incisive thoughts in the hard sciences and the social sciences are irreplaceable. This list of the smartest living people needs Chomsky on it.
#315 on The Greatest Minds of All Timesee more on Noam Chomsky