The different properties of infinitive constructions in natural languages pose a challenge for the explanatory power of syntactic theories. This paper develops an alternative to monosentential or bisentential analyses for causative and perceptive constructions: verbs like "see" or "let" embed a complement that is interpreted as a Davidsonian situation. Based on this semantic foundation, a universal syntactic model of the constructions is developed, which specifies the different syntactic properties of resultative constructions, particle verbs, unaccusatives, medial constructions, etc., for German, English, French, Italian, and Spanish. The author argues that invariant semantic properties are encoded syntactically in different ways across languages, and that these encodings influence distribution.