I share Stuart Elden’s hesitation for ranking philosophers, though I could get pulled into that conversation pretty easily. He also answers a follow-up question I was going to have about Leibniz—what biography would someone recommend, though there aren’t that many out. In any case, here’s his ranking:
I’m a little reluctant (and/or unqualified) to rank philosophers across time and space – and there are lots of criteria, including ‘best’, most important, most influential, etc. – but if pushed I’d say Aristotle for the ancient world; and Kant for the moderns. I think medieval thought is hugely important, and Aquinas has to be the standout figure there. After that it’s much more open to question. But I think you could make a strong case for Leibniz being the most accomplished thinker of his time, and it was a pretty remarkable time – Descartes just before him, and Hobbes, Locke, Spinoza, Pufendorf, Newton as contemporaries. I think Graham nails it with the comment that Leibniz is “quite staggering in his integration of Modern with Scholastic philosophy”; at the very least he’s a hugely important transitional figure.
Here’s a perhaps naive question, but isn’t it generally the case that there are really quite few political philosophy classes that include this period for anything other than the English? Certainly, as a political theory student, it was as if the continent didn’t exist—which is perhaps the most enduring Continental/Anglo-American split.