Bear in mind that this is not a question of who your [i]favourite[/i] philosopher is, but who you think is most influential as a whole. Of course, if you're a libertarian, you might be biased towards choosing someone like Ayn Rand, but try to be as neutral as possible. So, discarding my (obvious) preference, I'll have to go with Immanuel Kant. Despite the fact that his ethics were retarded. [u]Socrates, [url=http://en.wikipedia.org/wiki/Plato]Aristocles (Plato)[/url] and Aristotle are barred from the competition. [/u]