Isaiah Berlin famously took Archilochus' line about foxes and hedgehogs -- "The fox knows many things, but the hedgehog knows one big thing" -- as the occasion for an ad hoc divvying of human beings into "two kinds of people":
There exists a great chasm between those, on one side, who relate everything to a single central vision, one system, less or more coherent or articulate, in terms of which they understand, think and feel – a single, universal, organizing principle in terms of which alone all that they are and say has significance – and, on the other side, those who pursue many ends, often unrelated and even contradictory, connected, if at all, only in some de facto way, for some psychological or physiological cause, related to no moral or aesthetic principle.It's at least a 15-minute party game to name various figures and have people slot them into one of the categories (Hitler? "Hedgehog." George Elliot? "Fox." David Byrne? "Fox." "No, hedgehog!" Isaiah Berlin? Fox, definitely.) Berlin of course uses the categorization to push beyond it, arguing that in Tolstoy's case we have a fox who struggled to be a hedgehog. Another question, less universally suitable for parties, is to compare this human dichotomy to other ways of sorting thinkers into Type A and Type B; for example, Critical and Constructive philosophy (these are David Pears' terms in his brief book Paradox and Platitude in Wittgenstein's Philosophy):
Does [philosophy] explore the world like a science, but in a deeper and more general way? Or does it only examine our own thinking about the world? And why is the object onto which it is most sharply focused so often itself? ...The history of philosophy reveals a pattern...of oscillation between two very different endeavors: expansive exploration and anxious self-criticism....critical philosophy is needed to sharpen the tools that are used by constructive philosophy. But....constructive philosophy has often claimed to explore a field of its own...and that is a claim that critical philosophy...has strenuously rejected.Chris Vitale at Networkologies drew a distinction last year between Apodictic and Descriptive philosophies. He spins it out in interesting ways, but here I'll just give his preliminary account:
Apodictic philosophies are those which propose that that we can say something about the world about which we can be certain.... These philosophers often use terms like ‘proof’, ‘proven,’ and ‘truth,’ and when these notions are attacked, argue that there may be human error, or perhaps we haven’t gotten there yet, but that somewhere, somehow, notions like truth, certainty, proof, etc., are possible. ... Descriptive philosophers believe that there are many possible descriptions of the world, and some are better or worse than others, often depending upon notions like context, or use, but that there are no philosophies that are inherently correct or true.And in his yet-to-be-translated (anyone? anyone?) Spirit of Nihilism, Mehdi Belhaj Kacem bases a distinction between the ontological right and left on Heidegger's and Badiou's differing use of the vocabulary surrounding the term Event:
hermeneutics reckons that it is possible to found the site, the site that will give rise to the event. We will call this metaphysical tendency the ontological far right. [A] second tendency holds that it is absolutely impossible to found the site. Rather, it is the site that "founds," meaning that it gives rise to, without any preparation, any willfulness, or any decision, the event. We will call this metaphysical tendency the ontological far left.It's easy to see how any of these might overlap, but they are not equivalent distinctions.
Nor is the one I'm going to propose, which comes to light most overtly when philosophers comment upon the history of philosophy, and most especially when philosophers say things like "Hitherto, philosophers of no matter what school have always tried to do X." This is almost always preliminary to making one of two moves. On the one hand there are perennialists, who follow up by saying, "let us therefore see what it is that is required to do X in our day," (or sometimes, more grandiosely, "to do X right"); on the other hand, there are revolutionaries, who say, "but henceforth, we shall do Z instead." These latter usually mean "Hitherto, philosophers have always fallen prey to X; but now we see how we may set things aright, and do Z." More modestly, they may say, "X has always sent out its insidious siren call; here is my new proposal to inoculate us,at least for the short term." In any case, whether modest or grandiose, the essential difference is that for perennialists, X is a feature; for revolutionaries, X is a bug.
For now, I am leaving X undefined. It could be "explaining the world," or seeking mystical illumination, or apprehending the Whole, or stopping the wheel of karma.
The example of a revolutionary you are likely thinking of is Marx in Theses on Feuerbach, but there are revolutionaries of all sorts. Brassier is a revolutionary, as is Dennett (on my read); so too is Laruelle. But so was Kant and so was Descartes; so too Bacon, St. Paul, the Buddha.
On the other hand, Badiou is every bit as much a perennialist as his bête noire Levinas; so too Aquinas and so Leibniz; so too Plato and Aristotle; so too Confucius and Mencius; so too Ravaisson, or Rosmini.
As should be clear from the above list, perennialism does not exclude making a drastic conceptual revision; the important criterion is to what end the revision is made. But the more grandiose the perennialist, the more easily mistaken they can be (even by themselves) for a revolutionary. Thus, e.g., Vico is a perennialist despite his "new" science, and Hegel is a perennialist, who looks like a revolutionary in his claim that now we have wisdom (or at least, he did). (On the other hand, Nietzsche's claim that he divides history in two really is the claim of a revolutionary.)
Perennialists often comment upon revolutionaries, pointing out how the revolutionary was really just doing X all along. (One of the clearest instances I know is Gilson's Unity of Philosophical Experience.) But on the other hand revolutionaries are also likely to follow revolutionaries, pointing out how their predecessor succumbed to X despite himself, but this time, this time for sure. Thus Heidegger's reading of Nietzsche: "Overturning Platonism is still Platonism."
I said that this distinction comes to light mostly when philosophers remark on history, but it need not be the center of their attention. While revolutionaries do usually make some kind of sweeping pronouncement on the past, they are usually much more eager to get on with their new program. But perennialism may be almost entirely implicit. A thinker like Robert Brandom engages extensively and sympathetically with the tradition, but Whitehead's work, while hardly disengaged from his predecessors, is no less perennialist, despite all the surprising new turns of his thought.
It's tempting, maybe, to see perennialists as hedgehogs, but clearly a revolutionary might also know "one big thing," so Berlin's dichotomy doesn't map onto this one. Nor does Pears', even though one of Pears' examples of "Critique" is (for obvious reasons) Kant. Vitale's two flavors have been with us from the beginning, even though what he calls "Descriptive" has perhaps been in the minority. (On the other hand, there seems to me a good case for guessing that many who Vitale would identify as Descriptive philosophers have been Berlinian foxes.)
To me the most interesting comparison would be with Belhaj Kacem's, but I am not confident that the match would be very close. Since I haven't read his book, which is in French, but only Alexander Galloway's excellent introduction and commentary, I can't say for sure, but it seems fairly clear to me that, despite a certain facile equivalence some would like to draw, perennialism does not in any simple way correlate with "conservativism," (small-c or large-), let alone with reactionary. Note that I do not mean by "perennialist" a propounder of "the perennial philosophy" a la Aldous Huxley's famous book, but simply a position that sees philosophers as always engaged in the same project -- regardless of their answers. Thus on my reading, Julius Evola or Ken Wilber is certainly a perennialist; but so is John McDowell or Michael Dummett or Judith Butler. Evola and Wilber are doubtless close enough to the Huxley mold for these purposes, McDowell and Dummett and Butler, rather far; but more to the point, they are figures from all over the political spectrum. A revolutionary, by contrast, believes there can (and should) be a break (not just a development) in the history of the project of thinking -- by which rationale, Machiavelli is as much a revolutionary as Bakunin, and Galileo as much as Kierkegaard.
Of course like all such schemes, this one is rife with crossovers; and one can be a perennialist in some matters and a revolutionary in others. Wittgenstein wanted badly to be a revolutionary, but he was too honest. On the one hand, he thought he had a way of resolving problems by dissolving them, a method he justifiably considered new; but on the other, he knew very well that the questions he approached thus were venerable and not at all stupid -- were, in a word, perennial. Heidegger, less honest, posed as a kind of radical perennialist; he was, rather, deeply ambivalent. Cassirer, who was the real thing, sized him up well in his diary during their famous confrontation at Davos: "Heidegger speaks no longer as a commentator but as a usurper."
Another interesting case is Derrida. Easy to say "revolutionary," but Derrida knew very well that there was no "final overcoming of metaphysics;" I tend to read him as a perennialist who saw the perennial nature of the revolutionary urge. This is also my stance, and, I suspect, was also Plato's.