Who would you say is the most influential philosopher of all time? I am taking about a philosopher who has not just made a fundamental impact on Western philosophy, but also on Eastern philosophy, and all the other ones of which I am not aware. I am also not taking about the best, greatest, or most known, loved, cited, quoted, or recognized. My question is solely based on influence, whether it was good, bad, both, or neither.
I will take a shot at this question, though with great hesitancy. The three philosophers that pop to mind are Socrates, Plato, and Aristotle. And because you are requesting a single philosopher, I would place a small wager on Plato for it is through Plato that we learn the most about Socrates (there are other sources, but Plato's is the richest, I suggest) and Plato was Aristotle's teacher (for about 20 years). A great 20th century British philosopher once observed that the history of philosophy is the history of footnotes on Plato. That, of course, over-states things and perhaps sacrifices accuracy to wit. In good conscience, I must confess that I understand myself as a Platonist --so it may be that I am not the most objective in such matters. Although A.E. Taylor's work is a bit dated, I highly recommend his work on Plato --very accessible and puts Plato in context.