“Philosophy,” the early German Romantic writer Novalis remarked, “is homesickness”: the desire to be at home everywhere in the world. If that’s right, then surely philosophers should also want to be architects—or at any rate, to build houses for themselves.

And yet, as far as I know, no great philosopher has ever successfully made the transition from the armchair to the drafting table. In fact, the only one who even attempted anything remotely like it was Ludwig Wittgenstein, who in the middle of the 1920s helped supervise the construction of a modernist townhouse in Vienna for his sister Margrethe. Technically, the architect on the project was Paul Engelmann, a friend of Wittgenstein’s who had been a student of the pioneering modernist Adolf Loos. But so particular was Wittgenstein—and so demanding—that Engelmann eventually came to see the philosopher as the real author of the final product.

This was very much a reflection of Wittgenstein’s personality: neurotic, perfectionist and overbearing. Born in Vienna into one of the wealthiest families in Europe, Wittgenstein had studied aeronautical engineering before becoming obsessed with the foundations of mathematics, notoriously turning up unannounced to Bertrand Russell’s rooms at Cambridge, before rapidly convincing everyone there that he was a genius. His first book, the Tractatus Logico-Philosophicus (1921) was gnomic and austere, comprising 525 numbered declarative statements.

Wittgenstein believed that with the Tractatus, he had solved all the important problems in philosophy—which left him with the rest of his life to live, doing real stuff in the real world. Before attempting to become an architect, Wittgenstein had trained as a village schoolteacher, which went disastrously. He also worked as a gardener and considered becoming a monk.¹

Wittgenstein’s plans for his sister’s house were perfectionist to the point of megalomania: He spent two years making sure that every detail fit his specifications exactly. Everything was ultra-modernist: straight lines, white walls, stone floors, no carpets, bare light bulbs. Just as the project was almost completed, he insisted that one of the ceilings be raised 30 millimeters, so that the room would have the exact proportions that he wanted.

But it was probably always going to be impossible for Wittgenstein, or anyone, to be satisfied with the result. When experienced in person, the house, which now forms part of the Bulgarian Embassy, is manifestly a failure—an empty maze of light and glass. Wittgenstein himself came to believe that the building was too austere, with “good manners” but no “primordial health.” His sister Hermine remarked politely that while she admired the house, it seemed “to be much more a dwelling for the gods than for a small mortal like me.”

In the end, the house did leave a major legacy—in its impact on the development of Wittgenstein’s thought. Shortly after completing it, Wittgenstein returned to Cambridge, and philosophy. He had grown dissatisfied with his thought as expressed in the Tractatus, realizing, in part through the example of the awful perfection of the house he had built, that its icy purity was too detached from reality to ever be relevant to life as lived.

In a famous remark from his second great work, Philosophical Investigations, Wittgenstein compares thinking to walking. “We want to walk,” he says, “so we need friction.” Philosophy desires to feel at home in the world. But to do this, it must take in all the rough and tumble of the mess and chaos that Wittgenstein sought, impossibly, to eliminate from the home he built. “Back to the rough ground!”