Definitely Aristotle. His work on epistemology alone, though flawed, ranks as the highest pinnacle of intellectual achievement.
Then there’s the anonymous person, thousands of years ago, who first connected a concept with a specific sound, creating the first word.
No offense, but that’s completely untrue. Aristotle’s method was to explain something with a theory. The value of the theory was then wieghed by whether or not it sounded good. Experimentation was not only unnecessary, it was openly discouraged. For that matter, so was observation.
Aristotle’s explanation of why women have less teeth than men is a cliche, but an illustrative one. Not only is Aristotle’s theory wrong, he didn’t even get his facts right.
God: “I even told them, 'Thou Shalt Really Try to Get Along with One Another.”
Dean: “Did it work?”
God: “I can’t say for sure. Everyone was slaughtered by the followers of the god in the next valley who told them to kill everyone who didn’t believe in him.”
–Terry Pratchett, The Last Continent