This monograph offers a new analysis of West Germanic ‘Infinitivus Pro Participio’ (IPP) constructions, within the framework of Optimality Theory. IPP constructions have long been problematic for syntactic theory, because a bare infinitive is preferred over the expected past participle. The book shows how the substitution of the past participle by the infinitive in IPP constructions can be captured straightforwardly if constraints are assumed to be violable. The basic idea is that IPP constructions are exceptional because they violate otherwise valid rules of the language. Thus, IPP is a ‘last resort’ or repair strategy, which is only visible in cases in which the past participle would be ‘even worse’ . Furthermore, as the choice of Optimality Theory naturally leads to a crosslinguistic account, the book systematically examines and compares infinitival constructions from seven West Germanic languages including Afrikaans, Dutch, German, West Flemish, and three Swiss German dialects.