His book on Fascism, the Myth of the State was an interesting experiment that anticipates a lot of recent state theory, to the effect that it is a relationship rather than a thing. The book, though, is marred by the apparent reading of Carlyle's Sartor Restartus as straight when in fact it is a wildly tongue in cheek parody of scientism. A misreading that rather calls into question Cassirer's great qualities as a critic.
He debated Heidegger at some turning point emergence of German irrationalism, in Davos in the 20s, C. representing German rationalism, H. existentialism.
-- James Heartfield