In this poster I discuss the syntax of the Early Irish so-called autonomous verb form (which is normally termed 'passive' in the descriptive grammars). It is argued that that this verb form can be used in at least three different construction types at the time of Old Irish: the canonical passive, where the lower role maps to the subject function, the impersonal passive, where the lower role maps to the object function, and the active subject impersonal, where there is active mapping to a phonologically null subject with an arbitrary interpretation. In the subsequent diachronic development, the canonical passive disappears and the impersonal passive takes its place. The construction types are defined using the revised LMT from Anna Kibort's work (2007 in particular).