Massam (1992), challenging the view that the presence of an implicit argument is essential to middles, argues that middles should be defined in terms of genericity and modality. This paper shows that Massam's hypothesis is factually untenable. Genericity and modality are only typical, not essential, properties of middles. Furthermore, middles in Massam's conception do not form a natural class with middles as normally understood. Rather, the presence of an implicit argument is a defining characteristic, as is widely accepted.

It is further shown that in order to handle an implicit argument properly, middles need to be represented by conceptual structure in the sense of Jackendoff (1987a, 1987b, 1990). The proposed analysis of middle by means of conceptual structure accommodates even the implicit argument of middles that express specific events.