How the Critique of Pure Reason was written. “Hegel’s Phenomonology was written in very much the same way,” and so was Sartre’s Critique

When the Critique of Pure Reason appeared, Immanuel Kant was fifty-seven. Berkeley and David Hume published their masterpieces in their twenties; Arthur Schopenhauer his at thirty-one. Soren Kierkegaard died at forty-two, Friedrich Nietzsche stopped writing at forty-four, B. Spinoza died at forty-five, and Hegel, who was a late bloomer, published his first book at thirty-six and his last at fifty-one. As early as June 7, 1771, Kant wrote Marcus Herz that he was at work on a book with the title "The Limits of Sensibility and Reason" and, after having gone over all the materials and weighing and fitting together everything, had finished the whole plan. Kant kept thinking that he would publish his magnum opus in roughly three months' time and felt so sure of this that he could promise it "almost certainly"—and perhaps said so in writing to increase the pressure on himself.