Tractatus Logico-Philosophicus by Ludwig Wittgenstein (1921)

Seven sentences hold up the entire book, the first six branching downward into decimals like a logical tree, the seventh standing alone: whatever we cannot speak about, we must pass over in silence. Ludwig Wittgenstein worked out this architecture in notebooks he carried as a soldier through the First World War, finishing it as a prisoner of war, certain he had dissolved every genuine problem philosophy had ever posed. The pages build a theory of how a sentence pictures the world, fact answering to fact, and then press toward the border of what language can reach at all. Ethics, beauty, the meaning of a life: all of it, he insists, lives on the far side of that border, where nothing can be said and everything that matters is merely shown. Then each proposition, he tells you, is revealed as a rung; understand them and you throw the ladder away and see the world rightly. Few books ask to be climbed only to be abandoned, or make that abandonment feel like the only honest place to stand.