I was reading way down my list of things I wanted to blog about that I never got to, and I found Kenny Pearce's Five Favorite Philosophers post from December 2006. (Sadly, this was only 60% of the way down in my huge file of things to be blogged about that I haven't gotten to, and the latest stuff is at the top!) I'd started the post but hadn't completed it, and I thought it was a worth task to be completed, so here we go:
1. Augustine: On every test checking one's views with actual philosophers, I come out closest to Augustine. When he disagrees with Aquinas, I usually side with him. He was one of the most intelligent Christian thinkers to interact heavily with philosophers in a systematic way, and I think his criticisms of his contemporaries, if occasionally exaggerated, are nevertheless accurate enough assessments of the problems with those philosophers' positions. His emphasis on ordinary language is similar to one of my own complaints about many influential philosophers. He rightly rejected the high-standards view of knowledge endorsed by Plato, the ancient Skeptics, Descartes, Locke, Hume, and most philosophers of the 19th and 20th centuries up until the 1980s or so. After all, such views use the terms for knowledge in ways that simply don't match up to ordinary usage. He adopts a view on the passions that's very similar to the Stoic view but denying their strange definition of emotions as faulty reasoning, again emphasizing ordinary language over philosophers' arbitrary redefinitions. I'm not sure his view of freedom is coherent, unless he changed his mind when writing <i>City of God</i> between the single-digit books and books 12-14, but his view is one of the better ones in the ancient world. His view that ethics is primarily about rightly-ordered love of what's best seems to me to get closer to the heart of what's most important than any other ethical thinker.
2. G.W. Leibniz: Leibniz was by far the best of the early moderns. He retained much of what was good from the medieval philosophers, a lot of which had been rejected by his contemporaries. He's the first I know of to use the philosophical device of possible worlds, but he does it better than contemporary philosophers by recognizing that worlds are what God could have created (and thus God isn't in any possible worlds but is existent for all of them). I go back and forth on the Principle of Sufficient Reason as he states it, although something like it has got to be true, and a lot more of what he derives from it is true than most philosophers accept today. His systematicity and careful attention to detail place him as one of the greats, and it's too bad much of his work is barely studied today. A significant portion of Saul Kripke's game-changing work in the 1970s and 1980s was present in Leibniz's responses to John Locke. He (and not Locke, as some claim) was responsible for the first modern discussion of personal identity that I can find. Everything halfway decent that Hume had to say about free will and compatibilism (one of the few issues Hume has anything to say about that's worth paying attention to) was anticipated by Leibniz.
3. David Lewis: Dean Zimmerman joked at Lewis' memorial service that when you cross David Hume and Gottfried Leibniz, you get David Lewitz. Lewis was more responsible than anyone else for bringing metaphysics back to its rightful place as the central branch of philosophy in the 1980s and 1990s. There's far too much of David Hume in Lewis' views for me to get too excited: e.g., on causation (facts about causation depend merely on what happens and not the obvious truth that it's the other way around), the ontological status of possible worlds (they all exist in the same way our world exists), the existence of God (for him only in other possible worlds, but that sort of God isn't God, since he doesn't necessarily exist), consequentialism in ethics (consequences are the only morally relevant consideration for how we should live). But his approach is much more Leibnizian, in that he actually gives arguments for his views, something Hume rarely does (at least not while accurately representing the views he criticizes and not in a way consistent with all the things he wants to say). Lewis was in many ways (but unfortunately not in some important ones) a model philosopher. The entire field of metaphysics today has been shaped by him in ways that are largely good, and the ways that aren't are ripe for response from those who have views that are closer to the truth. It's hard for me not to admire the comprehensive and systematic work that his career produced, and I'm glad to have been able to meet him shortly before he died. In my view he's by far the most important philosopher of the 20th century.
4. The Stoics: This is a bit of a fudge, but I can't pick one. I really like Chrysippus for his comprehensive presentation of canonical Stoic thought, but he had some really weird views about time. Cleanthes was never viewed as quite as good a thinker, but he was the first person to give the correct solution to foreknowledge problems and related issues about time. Other than that issue. Chrysippus is my favorite, but when I discovered that about Cleanthes my opinion about him went way up, because it took until Aquinas to get that right in a more explicit way than what Cleanthes had come up with centuries earlier. I don't like every way the Stoics express their compatibilism about freedom and determinism, but it's closest to the truth of any view I know of before Augustine and Thomas Aquinas, whose views capture something not present in any Stoic work I know of but may also go too far in distancing themselves from the Stoics. Their insistence on final causes in nature in a stronger way than even Aristotle acknowledges (because they do believe the divine universe has a providential plan) makes them the closest thing to Christian views on nature among the ancient Greco-Roman philosophers. They come the closest in their time to anticipating reliabilism in epistemology, a view that I find absolutely obvious once it's considered and understood but is difficult enough that it has few predecessors in the history of philosophy (although Augustine is another exception).
5. Plato: I'm not usually impressed by his arguments, at least in terms of their convincingness. He regularly presents arguments that rely on premises his opponents wouldn't grant. But unsupported premises don't mean the arguments are unsound, because the premises are often the sort of thing that I find intuitively true, and I can't understand how anyone can deny them, even if I know that many have denied them. Most of Plato's arguments are like this, and his presentation of a great many issues seems to me to show a good deal of wisdom in thinking through things in ways that make many more recent philosophers seem to have regressed. Even when he seems extreme, I think it's because he's presenting things in a mode of thinking ideally, and he often takes it back once you introduce more ordinary considerations for how things will work in real life (e.g. his <i>Republic</i> view of government that amounts to benevolent dictatorship gets presented in the <i>Statesman</i> as ideal if it worked but unworkable in practice, a view that I find absolutely compelling and quite welcome to a theist, for whom the unworkability with human government is easily removed with a divine ruler. When he and Aristotle disagree, I tend to be more often on his side. His picture of virtue as moral health seems to be to ground a much broader view of what morality includes, especially moral obligations to oneself, and that seems right to me.