Malraux uses the form of a novel to propound endless paradoxes. The Walnut Trees of Altenburg is chock-a-block full of existential paradoxes concerned with life, death, and --- what else? --- existence. He gathers several professors together to present a discussion of his paradoxes,

The greatest mystery [one of them says] is not that we have been flung at random between the profusion of the earth and the galaxy of the stars, but that in this prison we can fashion images of ourselves sufficiently powerful to deny our nothingness.

In this way, Malraux casts his net of mystery directly into the writing. It's Malraux, but it is given to one of his characters. In The Walnut Trees, it is put into the hands of an ostensible friend of Friedrich Nietzsche.

Once, in Turin, he tells us, Nietzsche went crazy, and his friend had to get him back to Basel. They had only money for a third-class ticket:

The train was more or less full of poor people, Italian workmen...next to him was a peasant girl, with a hen. The hen kept poking its head out of her basket; the girl kept shoving it in again. It was enough to drive one mad --- yes, mad! What could it have been for a sick man? I thought something frightful might happen.

The train entered the St. Gothard tunnel, which had just been completed. In those days it took thirty-five minutes to go through --- thirty-five minutes --- and the carriages, the third-class one at any rate, had no lighting. Swaying about in the dark, the smell of soot, the feeling that the journey would never end...In spite of the noise of the train on the metals, I could hear the hen's beak pecking at the wicker-work, and I was on tenterhooks. Supposing a crisis occurred in this darkness?

All of a sudden --- you...you know that several of Friedrich's works were still unpublished --- a voice began to make itself heard in the darkness, above the din of the wheels. Friedrich was singing --- enunciating clearly, though when he talked he used to stutter --- he was singing a poem which was unknown to us, and it was his latest poem, Venice. I don't like Friedrich's compositions. They're mediocre. But this song...well, by God, it was sublime.

He had stopped long before we reached the end of the tunnel. When we came out of the darkness, everything was as it was before. As it was before...the same wretched carriage. The same peasant girl, the hen, the workmen, and this dentist. And ourselves --- and him, in a daze. That mystery you have just mentioned, I have never since felt it so strongly...something very strange was happening: the song was as strong as life itself... in that carriage, now, and sometimes since --- I merely say: "sometimes" --- the millennia of the starlit sky seemed as completely wiped out by man as our own petty destinies are wiped out by the starlit sky.

Ah, Malraux. Putting philosopy in a third-class coach, along with Friedrich Nietzsche, gone balmy, singing "Venice," in a lovely voice. What could be simpler than tales set like these, where such rich insights occur within pecking distance of a hen, being carried by a peasant maid.

I always admired their gall --- Sartre, Camus, Malraux). That they could put the most sublime arguments in a novel, set in Algiers, or in revolutionary China, or in hell. They pretend to be telling a story, when, in truth, they are telling a Truth. And they are never satisfied with one single Truth. Just so, in The Walnut Trees of Altenburg, Malraux concludes with a question that is no question at all:

To the question "what is man" we're blindingly ready to answer:
"Man is what he conceals."