I recently came across a philosopher – or rather, an historian of philosophy – named Robert Pasnau. He is Professor of Philosophy at CU-Boulder, and he edited the two-volume Cambridge History of Medieval Philosophy (2010) and the annual Oxford Studies in Medieval Philosophy. For all you Thomas Aquinas lovers, his 2002 monograph, Thomas Aquinas on Human Nature (Cambridge UP), won the American Philosophical Association Book Prize.

He had this to say to prospective graduate students of philosophy. (You can read his entire letter here.)

The discipline of philosophy benefits from a serious, sustained engagement with its history. Most of the interesting, important work in philosophy is not being done right now, at this precise instant in time, but lies more or less hidden in the past, waiting to be uncovered. Philosophers who limit themselves to the present restrict their horizons to whatever happens to be the latest fashion, and deprive themselves of a vast sea of conceptual resources.

If you think you have original philosophical thoughts in you, they can wait – indeed, it’s better to let them wait until you’ve had the chance to develop the philosophical breadth and depth to make the most of them…

[M]any philosophers today are presentists – they think that the only philosophy worth reading has been written in the last 100 years, if not the last 30 years. This attitude is hard to justify. The historical record shows that philosophy – unlike science and math – does not develop in steady, linear fashion. Perhaps the very best historical era ever came at the very start, in Socrates, Plato, and Aristotle. If that was not it, then one has to wait some 1600 years, for the century from Aquinas to Oresme, (Who’s Oresme?, you may ask. Exactly.) or wait 2000 years, for Descartes through Kant. I’m leaving out important figures, of course, but also many quite fallow periods, even in modern times. Maybe subsequent generations will judge 2011 and environs as the highpoint up until now of the whole history of philosophy, but I wouldn’t bet on it. Every generation of philosophers has been equally prepossessed by its own ideas.

Of course, I am no more capable than others of judging my own times, but certainly I am not alone in feeling some amount of dissatisfaction with the way philosophy looks today. Tyler Burge nicely expresses my own worries when he remarks, in the preface to his recent book, that “if philosophy is not to slide toward irrelevance and become a puzzle-game-playing discipline, good mainly for teaching the young to think clearly, some central parts of philosophy must broaden their horizons.” Burge mainly has in mind science as a broadening influence; I think the history of philosophy can play a similar role. Although a background in the history of the subject is obviously not a prerequisite for doing deep and original work, it helps, and I fear the discipline’s present collective neglect of its past contributes to its often insular character.

There you have it: read the old stuff. The new stuff ain’t new.