Intelligence is a nebulous concept, one that I suspect lacks meaning altogether. Does intelligence refer to brainpower, or to problem solving ability? Is there any difference? Does intelligence perhaps refer to something else, like creativity or intuition? And what do we even mean when we refer to those things? Is intelligence measured by potential or performance? If potential, doesn't this change throughout one's lifetime (if for no other reason than that the physical structure of our brains changes)? If performance, isn't intelligence then nothing more than a statement of historical intellectual triumphs rather than an indicator of future insights? And how do we know that there is even a smartest person alive? Settling on a list of the ten smartest people is probably no less absurd than generating a list of the ten biggest numbers. The concept of intelligence is not clear cut, but this list certainly is.
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.
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.
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.