In this thesis I provide an analysis of middle voice sentences (as in The book reads well, El libro se lee bien, Das Buch liest sich leicht) in which the characterizing feature of middles is a mismatch with respect to predicate adicity and the number of argument expression occurrences in the syntactic structure. Throughout the thesis I rely on the distinction between linguistic types and linguistic tokens. Thus, although it might rightly be said, when considering orthography or phonology, that in the sentence Lolita si legge facilemente, there are two items: si and Lolita, we can also rightly say, when considering syntax or semantics, that together si and Lolita constitute a single abstract object. A significant feature of the analysis is indeed the proposal that the syntactic subject of middles and the weak reflexive together formally constitute a single syntactic object. The analysis predicts the various properties of the weak reflexive that appears in many languages' middle voice sentences, including their Case, referential, and agreement properties. Taking the aforementioned mismatch to be the core characterization of middles predicts that they are morphologically and semanically less restricted than previously thought. Data presented in the thesis support this conclusion.