From the section on Sartre in Clive James's Cultural Amnesia
[Jean François] Revel, heartening in his impatience with Sartre’s ponderous folderol, usefully records Kierkegaard’s threat to Hegel: that he would send to him a young man who was in search of advice. Kierkegaard’s menacing insinuation was that Hegel would have to either get down to brass tacks or he responsible for the young man’s bewilderment. Revel also, and even more usefully, suggests that we should make the same threat to Heidegger. One says “even more usefully” because although there is something to be said against the belief that Hegel’s obscurity is never meaningful, there is nothing to be said against the belief that Heideggers’s obscurity is always meaningless. Hegel was trying to get something awkward out into the open. Heidegger was straining every nerve of the German language to do exactly the opposite. More than half a century later, the paradox has still not finished unravelling: it was Heidegger’s high-flown philosophical flapdoodle that lent credibility to Sartre’s. It was a paradox because Heidegger was an even more blatant case than Sartre of a speculative mind that could not grant itself freedom to speculate in the one area where it was fully qualified to deal with the concrete facts—its own compromises with reality. But merely to call Heidegger a “more blatant case” shows what we are up against. The case is still not clear, and in the years when Sartre and Heidegger were in a supposedly fruitful intellectual symbiosis, it was still not even a case: Heidegger’s involvement with the Nazis was thought of as a flirtation. The means scarcely existed for anyone—philosopher, philologist, literary critic, journalist or clinical psychologist—to point out the truth which has since become steadily more obvious, even if it does not appear axiomatic yet: that these two men, Heidegger and Sartre, were only pretending to deal with existence, because each of them was in outright denial of his own experience, and therefore had a vested interest in separating existence from the facts. Will it ever be realized that they were a vaudeville act? Probably not. Even George Steiner, who can scarcely be accused of insensitivity to the historical background, persists in talking about the pair of them as if they were Goethe and Schiller. Those of us who think they were Abbott and Costello had better reconcile ourselves to making no converts.