In 1921, the philosopher Ludwig Wittgenstein published a short but highly influential book called the Tractatus Logico-Philosophicus. In it, he argued that language works like a picture: Once a proposition is known, it immediately conveys the logical form of the reality it supposedly represents, the same way that a picture conveys the visual form of the reality it represents as soon as it is seen. However, a proposition is only meaningful if it describes something that actually exists in the world. That statement must therefore be compared to reality to determine its truth value. For Wittgenstein, anything that could not be pictured this way, including many questions about ethics, emotion, or meaning, simply could not be talked about clearly. As he wrote in the book’s own famous closing proposition, “whereof one cannot speak, thereof one must be silent” (Wittgenstein, Ludwig. Tractatus Logico-Philosophicus. Kegan Paul, Trench, Trubner & Co., 1922).

Wittgenstein later extended this idea to mathematics. He argued that a contradiction inside a purely mathematical system was harmless, since the system does not describe or “picture” the real world the way an ordinary sentence does; it is simply a set of rules. In 1939, the mathematician Alan Turing attended a series of Wittgenstein’s lectures at Cambridge and pushed back on this idea. Turing argued that logical contradictions were not harmless: if one crept into the mathematics used to build something like a bridge, “the real harm will not come [from contradiction] unless there is an application, in which case a bridge may fall down” (Wittgenstein, Ludwig. Wittgenstein’s Lectures on the Foundations of Mathematics. University of Chicago Press, 1989). Wittgenstein disagreed, treating such contradictions as puzzles confined to language rather than real dangers. This assertion emphasized the need to compare statements to reality.

This debate shapes 33 Place Brugmann, which opens with a line from Wittgenstein and returns to his ideas throughout. Julian, himself a Cambridge math student, describes the actual Wittgenstein-Turing argument to Charlotte. Her father, Francois, and her husband, Philippe, both turn to the Tractatus, hoping its rules for clear thinking can make sense of a senseless war. Charlotte, who has colorblindness, has a different relationship to visible “facts,” and she questions Wittgenstein’s claim that “objects are colorless” but have color as part of their form (242). Through these responses, the novel asks whether logic alone can capture the full truth of lived experience, a question that grows more urgent as the world around the characters stops making rational sense and they must rely on less rational responses for survival, like hope.