Few approaches have been quite so polemical and have stirred quite so many different responses as space syntax. This article is not an introduction to space syntax; rather it aims to discuss its substantive reach and epistemological status. To this end I make use of one of the simplest – though not necessarily the best or easiest – ways of understanding something: namely, defining what something is not. This negative path will lead us to a series of observations concerning the nature of the theory in order to highlight, on the one hand, its main contributions, such as the emphases on social reproduction, co-presence and the embodiment of practice; its hybrid epistemology; its relational concept of space; and the reaffirmation of space as a living dimension. On the other hand, it shall discuss the limits of the theory concerning society–space relations: the reduction of social practice to movement, human interaction to social interfaces and encounter, and the actor to bodily presence; the primacy of syntax over semantics; the problem of time in the structuring of space; and the difficulties of theoretical contribution. Finally I look to discuss the theory’s place regarding distinctions between urban and sociospatial theories, and dilemmas to be faced in its future development.