The Underspecification of Past Participles

Are the past participial forms that occur in passive and perfect periphrases substantially identical or should they rather be distinguished into accidentally homophonous passive and perfect(ive) participles? This book discusses the long-standing mystery of past participial (non-)identity on the basis of a broad range of synchronic data from Germanic and Romance, eventually focussing on German and English as these draw the most relevant distinctions (e.g. auxiliary alternation, a passive auxiliar