Bresnan (1978:8-9, 1982:29, 2001:31) proposes that English has a general morphological process of participle-adjective conversion which enables any verbal participle to be used as an adjective. The phenomenon captured by the Participle-Adjective Conversion Rule has been used as key evidence from English that passivisation is a lexical relation change, not a syntactic transformation, and as such, it can feed lexical processes of derivational morphology. The discussion offered in this paper supports fully the lexical character of both passivisation and participial formation. However, it argues for a small but important revision to the formulation of the Conversion Rule. Specifically, the morphological derivation of participles does not engage the syntactic level of argument structure. The input to the Conversion Rule is a verb, and the output is a deverbal form (a participle) which is category-neutral between a verb and an adjective (i.e. it is both a verb and an adjective at the same time). Passivisation is also a derivation, but it is morphosyntactic: it occurs at the level of argument structure of the predicate and it is an operation on grammatical functions. A patient-oriented (derived) participle is passive only if it is used as the main verb of the passive construction. In the paper, all the points just raised are elaborated on and illustrated mostly with English examples.