I’ve been writing up some stuff on Herman Cappelen’s great new book “Philosophy Without Intuitions”:http://ukcatalogue.oup.com/product/9780199644865.do#.UAbFDTGe6qw. And it got me thinking about just what is distinctive about philosophy. You might have thought it was something to do with the use of intuitions, but Cappelen shows that isn’t right. Whatever intuitions are, there isn’t much ground for saying they are more prevalent in philosophy than in other disciplines.

So what is it? It’s not a trivial question, because there isn’t much obviously in common between what different philosophers work on. Just looking at my own colleagues, it’s hard to say what the common thread linking the work of Sarah Moss, Elizabeth Anderson, Chandra Sripada, Allan Gibbard, Victor Caston and Laura Ruetsche could be.

I sort of suspect there isn’t really a _principled_ answer to the question of what is philosophy. Rather, the answer as to why some things are done in philosophy departments and others are not will largely be historical, turning on some fairly contingent choices that were made in the formation of the contemporary academy.

To get a sense of how plausible this hypothesis is, I wanted to run a couple of little thought experiments. The experiments concern which departments house which questions. Here’s what I mean by ‘house’. For some questions, there is an obvious department (or small group of departments) to be in if you want to work on that question. If you want to work on what needs to be added to justified true belief to get knowledge, you should be in a philosophy department. If you want to work on the power relationships between the French monarch and aristocracy in the 18th Century, you should be in a history department (or perhaps a very historically oriented political science department).

Which departments house which questions changes over time. In the distant past, physics was part of philosophy departments. In a good sense, economics only split from philosophy in the early 20th Century. At Cambridge, which was at the time the most important place in the world for both disciplines, the economics tripos split from the philosophy tripos in 1903. To the extent that cognitive science was a recognisable field in the 1950s and 1960s, it was just as much part of philosophy as anything else.

Similarly, which departments house which questions can change over modal space. In some very nearby worlds, there are very few departments we would recognise as philosophy departments, even though there is much work on philosophical questions. That’s because in those worlds there are separate departments for moral philosophy and for logic & metaphysics, as there was at St Andrews traditionally.

But let’s focus on worlds in which there are recognisable philosophy departments. Here’s the question.

• For each sub-discipline in philosophy, how far into modal space do you need to go to find a world where it isn’t housed in a philosophy department?

I’ll put my views on this over the fold, so if you like you can think about this before seeing what I have to say.

For a few areas, it is easy to imagine them being in other departments, because they already overlap so substantially with work done in other departments. These areas (and the overlapping departments) include:

• Logic (Mathematics and Computer Science)
• Language (Linguistics)
• Decision Theory and Game Theory (Economics)
• Legal Philosophy (Law)
• Political Philosophy (Political Science)
• Feminist Philosophy (Women’s Studies)
• Philosophy of Physics/Biology (Physics/Biology)

Those are roughly ordered in terms of how substantial the overlap is between what goes on inside philosophy departments and what does on in other departments. It is perhaps a bit of a stretch to include Philosophy of Physics and Biology here, because physics and biology departments have on the whole moved away a bit from the kind of theoretical work philosophers do. But I think it’s easy to imagine them including more work we currently call philosophical.

It’s true that some work that’s currently done in philosophy of language doesn’t really overlap with much of linguistics. But a lot does. I think the paradigm of recent work in philosophy of language is the joint work on epistemic modals between Thony Gillies and Kai von Fintel, the existence of which is a pretty strong proof of the overlap between the departments.

I could perhaps also have included

• Aesthetics (Literature, Art History and Music)

but that would require knowing more about what goes on in literature, art history and music departments than I actually do.

And it isn’t much more of a stretch to include

• History of Ancient Philosophy (Classics)

There is obviously a fairly substantial overlap between classics and ancient philosophy, as evidenced by the number of very important academics that have joint appointments in philosophy and classics programs. It would require a bit of a culture change to classics to have all the work that’s currently done in ancient philosophy moved into classics, but it doesn’t feel like we’d be moving too far from actuality to imagine that culture change happening.

The next two are a bit trickier, but still could move without too radical a change to the academy.

• History of Modern Philosophy
• Philosophy of Mind

There are a few ways that history of modern could leave philosophy.

One is that existing history of science programs could incorporate more history of philosophy. It isn’t too hard to imagine there being much more work on Descartes and Leibniz in existing history of science programs, and if history of science included more history of economics, then Hume and Smith and possibly Locke would be included too. Once that happens, it is easy to see how a full blown history of modern program could be inside history of science.

A second involves the same thing happening inside history departments, but that is a bit more unlikely. Not completely unlikely, there is actually already “excellent work”:http://books.google.com/books/about/The_Good_Life_in_the_Scientific_Revoluti.html?id=hmZPs7GI_hMC in history of modern philosophy inside history departments, but perhaps unlikely.

A third involves there being more history of ideas departments, like there used to be at ANU. Again, perhaps that’s a little way from actuality.

Philosophy of mind is a little trickier, because it is such a diverse field. My sense of the most active work in the last decade could easily be duplicated by theorists who fit into psychology or cognitive science departments. Again, I’m not completely sure about the culture of psychology and cognitive science departments to say how much change would be needed to fit more philosophy into those departments, but my guess it would be a relatively small culture change.

That brings us to three fields that it would be hard to see moving _en masse_: Ethics, Epistemology and Metaphysics.

There are not massively distant worlds where there are departments of value theory covering basically current ethics and economics. In some of them I suspect to some extent that’s what Alfred Marshall had in mind when he moved economics out of philosophy at Cambridge. If you thought that Bentham and Mill had solved the very big questions in ethics, and that what was left to do was to work on applied questions, then you might think economics _was_ a general department of value theory. But it’s trickier to imagine a combined economics and ethics department where Kantian views are given much more attention. And it’s even harder to imagine much meta-ethics work going on in my imagined value theory department.

Some epistemology work, especially in formal epistemology, does obviously overlap with other disciplines. But it is hard to see work on, say, the proper formulation of the safety condition on knowledge fitting into anything like current departments outside philosophy.

Metaphysics might seem easy at first, though there are some overlaps with other fields. In those decades where metaphysicians care about things like causation and laws, there is overlap with other fields. (Remember that one of the most important books on causation in recent times was written by Judea Pearl.) But in those decades, like the last one, where the focus is on meta-metaphysics, it is hard to see it fitting into non-philosophy departments.

So that’s my ranking. It doesn’t match very readily with any popular sense of what’s ‘core’ to philosophy. Epistemology and metaphysics are hardest to dislodges, but logic and language are easiest. But it does perhaps help us think about why philosophy has ended up with the fields that it has.