I would go for Barrack Obama . Not because he is the president but because he became president in such a small age . Politicians spend their entire life to reach this powerful position and obama grabbed it in his first attempt .
As much as I admire Obama, I don't think that indicates he's the smartest man in history by any meants.
I'm not sure what 'smart' means. IQ scores aren't particularly impressive. (Just look at Mensa's membership.) Nor are they applicable to people in the past. And we need to remember that intelligence isn't necessarily the same thing as leadership or artistic creativity. But to answer the question in the subject line, my vote for smartest person in history would go to Aristotle. He was perhaps the first experimental biologist of whom we have record. Even today, his observations of the reproductive behavior tide-pool life is still impressive. He made contributions in fields like embryology as well. His physics was less impressive, but nevertheless very smart for its day and hugely influential until the scientific revolution replaced it with a new model. He more or less single handedly invented the field of logic in his two volumes on 'Analytics'. He was probably the first person in the world to write books expressly devoted to the study of deductive inference. The syllogism pretty much was logic for more than 2000 years, until the late 19'th century when logic began to be mathematized. He produced what has to be the first philosophy of science, suggesting the form that he thought a successful science should take. Unfortunately, his vision was probably too essentialist for modern taste. It was also excessively deductive, imagining a complete science as a set of truths represented as logical consequences drawn from a small set of basic axioms. That ideal was hugely influential though, even today when many contemporary philosophers of science seem to make their careers reacting against Aristotelian-style ideas. His ethics and politics are closely related and remain influential today. They try to understand what well-being and the good life are for human beings and develop a theory of virtue based on that. He was among the first to introduce terms like 'oligarchy' that we still use today. His metaphysics is derived from his biology, from his logic and from earlier Presocratic Greek philosophy. It's basically the way that he believed that ultimate reality must be so as to underlie and present itself as biological development and logical connectedness. The word 'metaphysics' comes from Aristotle, since the book that we today call by that name came after ('meta-') the 'Physics' in the ancient arrangement of Aristotle's works. His ideas on form and substance are still used in philosophy today. Aristotle's psychology reached few conclusions but contains many observations that contemporary psychologists still find interesting. And Aristotle had an aesthetics too. In fact, the whole arrangement of the many sub-fields of philosophy is largely due to Aristotle. Finally, the greatness of teachers is often reflected in the greatness of their students, and Aristotle's most famous student was Alexander the Great. Of course Alexander doesn't seem to have been much of a scholar himself, but at least he respected and appreciated scholarship and he included a team of scholars in his expeditionary force on its long journey east into India. The nerdier students contined Aristotle's style of inquiry in the 'Lyceum' that he founded in Athens, an educational/research institution that, like Plato's similar and slightly earlier 'Academy', was one of the first universities anywhere in the world. The Lyceum would send out expeditions to collect botanical specimens or to observe foreign governments, describing what kind of organizational constitution each used and trying to determine how well each worked in actual practice.
Newton.. we call it the Hubble Space Telescope but it was Newton who made the first "Newtonian scope". His laws of motion have been rather handy. I presume his model of gravity helped on a few space missions. I am not sure but I think he had a career in finance.. But you could make a list really.
I like Thomas Edison because of his ability for prolific invention. He amassed 1093 patents. One of Edison's famous quote is; I have not failed. I've just found 10,000 ways that won't work. If you consider his inventions and patents and all his dead end paths that had to be investigated to find the way, his brain was always working, at a time in history, when he had to pioneer so many things before he could pioneer other things.
