Jason Brennan wrote a nice reply to my defense of the great historical philosophers against Mike Huemer’s critique of them. I think the best way to respond is to outline two different ways of thinking about how to make progress in philosophy that I think roughly parallel how Brennan and I approach our own work. With those approaches laid out, I think we can explain why it strikes me as obvious that studying the great historical philosophers has value, and why Brennan is more skeptical. I. Particularist and Coherentist Methods As I see it, there are at least two ways to approach having true philosophical beliefs. One is a kind of go-it-alone strategy, where you simply try to determine what is true by looking at arguments, sorting through them, and believing accordingly. Big theories have worth, but they tend to distract us. Better to build small theories on different topics. On this picture, reading the history of philosophy has at most modest instrumental value, qualified by the danger of bias from being mentally trapped by these theories. Philosophers who pursue this more particularist strategy are thinking more like natural scientists do about the history of their own discipline. Why should physicists read Newton? Or Aristotle, for that matter? They shouldn’t, because their time is better spent working with contemporary methods, which are much better than old methods, at getting at the truth. Another strategy is to build big philosophical theories that attempt to capture a much broader stretch of philosophical territory and work to see if certain puzzles can be resolved from within the view. Here the philosopher plays a part in building systems of thought in conjunction with others – past, present, and future. From this perspective, philosophical theorizing is a social endeavor; and it’s long-term, extending perhaps over centuries. The payoff is a coherent worldview that can provide powerful answers to the big questions. Many great systems of thought work this way, especially with followers of Aristotle, Aquinas, and Kant. Philosophers who approach progress in this way have a kind of coherentist strategy. From this perspective, studying the great philosophers and their systems of thought is conducive to philosophical truth in part to help you decide which social endeavor to join, and if not, at least to get a sense for how to build one’s own philosophical project. It may well be that inhabiting a philosophical system and working out the results leads to some false beliefs. But for the coherentist, working within established frameworks is a better bet for discovering truth than doing one’s own thing. II. Schmidtz and Gaus on System-Building Both particularist and coherentist strategies have merit, and Brennan and I have chosen those two paths, perhaps in light of the examples set by our dissertation advisors (Dave Schmidtz for Brennan, Jerry Gaus for me). Schmidtz argues that philosophical theories are like maps, and many have readily detectable flaws. Accordingly, we should be hesitant to hold to any one theory too tightly, and should instead opt for pluralist approaches and addressing different problems in a more particularist manner. Here there is a central role for engaging work outside of the philosophy profession, since those professions make more progress and know more stuff. Gaus is especially worried that any large philosophical system runs the risk of bias and ideology. But unlike Schmidtz, he thinks that the process of building big theories and working within larger frameworks has a greater payoff than the more particularist, pluralist approach. So long as philosophers are in conversation with scientists, building philosophical theories as a social enterprise is likely to be productive. Philosophical systems by themselves can become ideology, but large-scale interdisciplinary theory-building is worthwhile. Brennan’s approach to philosophy is much more particularist, mine more coherentist. This has led Brennan to write a number of great books on quite different topics, despite having some underlying common themes. I have tended to work within the social contract tradition, and various dimensions of it: historical and contemporary, Rawlsian and Gausian, as well as putting the social contract tradition into conversation with the social sciences. These days I’ve been working at the intersection of social contract and social trust, which is a central endeavor in Must Politics Be War? III. Particularist and Coherentist Approaches to Great Historical Philosophers Particularists and coherentists will tend to disagree about the importance of the great historical philosophers for philosophical progress. History is more essential to the coherentist approach because the great philosophers created systems of thought that shed light on important questions. We cannot ourselves make much progress in a field without a deep familiarity with those systems of thought. If you think building big theories makes progress, then knowing the big theories, or at least some of them, will help you make progress. That’s at least so because they are good templates for building our own systems. But if you think building big theories is a bad way to make progress, then you’re view historical philosophers more like Brennan and Huemer. I think it is almost impossible to know which strategy is better for making philosophical progress overall, and that it is up to each philosopher to choose a more particularist or coherentist approach. I prefer to work within big systems of thought, and I think I can contribute more to the field in that way. I don’t trust myself striking out on my own. That’s one reason I find studying the history of philosophy essential to my work as a philosopher, and I can see why Brennan has a different view. But zooming out a bit, my sense is that philosophy needs both nimble particularists and patient coherentists, and so studying the history of philosophy is going to be essential for at least some strategies for making philosophical progress.