Between 1926 and 1928, the philosopher Ludwig Wittgenstein designed a house for his sister in Vienna (the Kundmanngasse). This book aims to clarify the relation between that house and Wittgenstein's early philosophy. The starting point of its main argument is a remark from Diktat für Schlick (c. 1932-33) in which Wittgenstein proposes an analogy between ornaments and nonsensical sentences. The attempt to extract from it an account of the relation between the Kundmanngasse and the Tractatus Logico-Philosophicus (1921) leads to the writings of Adolf Loos (whose influence Wittgenstein recognized). The discussion of Loos's writings suggests that the analogy should be understood, not as one between actual ornaments and nonsensical sentences, but as one between Loos's and Wittgenstein's uses of these notions. So understood, it favors the (so-called) resolute reading of the Tractatus and reveals that both Wittgenstein's use of 'nonsense' and Loos's use of 'ornaments' are means to the end of promoting self-understanding. The book concludes that both the Kundmanngasse and the Tractatus are results of Wittgenstein's efforts at this kind of self-understanding. These can be construed as ways of acknowledging our humanity, which in turn can be seen as a unifying element of Wittgenstein's philosophy.