Why do we have professional history of philosophy?

With more and more professional philosophers thinking of their enterprise as structurally akin to science, it is worth asking why they would keep historians of philosophy within the the intellectual division of labor of the profession. After all, we learn from Kuhn that at one point or another, science progresses while cutting itself of from its history and deploying at most mythic history for pedagogic purposes. I offer a taxonomy of four different existing strategies/justifications in the current professional practice. To facilitate discussion, I name names, but, of course, in practice there are many blended positions (including among the named ones).

1. History of philosophy is a service to the profession for teaching purposes. In particular, historians of philosophy can help explain and provide background material to otherwise obscure, canonical texts. Reconstructing arguments clearly and providing useful context helps colleagues teach complex material. (I have phrased this in such a way such that both whig and contextual approaches can fit this approach.) For example, while I nearly always disagree with say Don Garrett´s or Margaret Wilson's interpretations, I am always grateful to these when I am preparing a class. (Of course, Garrett's and Wilson's works can serve other philosophic ends, too!) Much of the best work in the field is, in fact, fundamentally service oriented in this way. Given that teaching philosophy is a noble enterprise this is not meant as disparagement. Of course, philosophy as normal science may well be able to do without canonical, historical texts and then make this role dispensable. (Of course, given that Plato, Spinoza, and Nietzsche are such enrollment winners, this would be a very foolish strategy.)
2. History of philosophy is a self-justifying practice to understand the past and, indirectly, perhaps the present philosophic situation. Many professional historians of philosophers are instinctively attracted to this. It is why they generally frown on so-called whig history. Much of the best methodological reflection in the area is concerned with promoting the right practices that enable one to get at some historical truth or insight. (Proponents allow, of course, that there may be unexpected or salutary philosophic insights to be gained from studying history of philosophy.) Dan Garber (my old supervisor) and Christia Mercer have long been a standard-bearer for such a view. More recently, my co-editors (of a forthcoming volume on the methodology of history of philosophy), Mogens Laerke and Justin Smith, have articulated very refined, competing versions of this approach. For them professional history of philosophy fits very nicely in the intellectual division of labor in professional philosophy. The only (not inconsiderable) risk is that philosophers give up ownership of their own history and farm it out to professional historians. (This has happened in economics during the last half century.)
3. History of philosophy is a source of renewal and inspiration, especially if one believes that the present philosophic situation rests in some sense on philosophic mistake. Michael Della Rocca's writings, for example, promote a recovery and revival of the principle of sufficient reason within metaphysics. Here history of philosophy has a dual role: (i) as a store-house of potentially promising arguments, strategies, positions, etc; (ii) as a cautionary and, perhaps, to be unmasked tale of error. It should be noted, however, that in this approach history of philosophy is fundamentally dispensable once the profession acknowledges error (say, about the principle of sufficient reason). Surprisingly enough while it is fundamentally at odds with the progressive tenor of the normal scientific ideal, it can offer an easy justification for itself: all paradigms require renewal, and historians of philosophy can be part of a portfolio of approaches that any discipline nourishes to help prepare the way for future paradigms.
4. Finally, one approach denies any fundamental distinction between philosophy and history of philosophy. All philosophy just is history of philosophy because philosophy is practiced against a historically given/conditioned/enabled framework or horizon. Given that philosophy is, in part, the activity that understands and questions itself (and all assumptions) the history of philosophy must be permanently interrogated, re-examined, (etc). Much of so-called Continental philosophy accepts something like this. (Charles Taylor has written eloquently about this in clear English.) On this view genuine philosophic progress (insight, etc) as opposed to mere lucky progress is only possibly by way of a re-articulation and re-coining of philosophy's history--something I advocate. Of course, for this approach to have enduring staying power within philosophy as normal science, it means that history of philosophy needs to be woven into the way philosophic paradigms are taught and how its worthy problems/puzzles are defined.