In this article we approach the phenomenon of the English middle voice from a functional-cognitive perspective. Assuming the distinction between representational and interpersonal layers of organization in the clause (Halliday 1985; Hengeveld 1989; McGregor 1997), we propose that the elements and relations that define the English middle are of an interpersonal nature. We argue that the characteristic relation between nonagentive subject and active VP in the middle cannot be generalized in terms of a specific process-participant relation, as has been attempted in the literature. It cannot be maintained that the subject entity is always affected by the action, nor that it brings about the action, which would obscure the difference between middle and ergative intransitive. Rather, we propose that the middle subject and finite are related to each other by what Talmy (2000) defines as a "letting" modal relation, which we characterize further as combining active and passive elements. Middles construe a subjective assessment of the subject entity, presenting it as lending itself to the action designated by the predicator, and as having properties that are actively conducive to that action. We also argue that this letting relation between subject and finite can be interpreted as the subjectification of the agentive-patientive relation between the lexical verb and the sole participant in an ergative intransitive clause. The shift towards subject and finite expressing a conduciveness judgment activates an inherent agent in the conceptual base of the predicate. This means that ergative verbs are always used transitively in middles and it explains why other transitive verbs can also occur in middles. In a language like French, which marks both ergative intransitive and middle reflexively, no further extension of middle predicates is possible. By contrast, both Dutch and, more marginally, English, which do not mark middles reflexively, also allow some intransitive and compound transitive predicates to be used in the middle voice.