The thesis has two aims: First, to produce compelling evidence for the so-called 'Clash Avoidance Requirement', a condition on the clausal grid level that no equally strong clausal stresses/accents may stand adjacent to each other; second, to demonstrate how the Clash Avoidance Requirement influenced syntactic usage throughout the history of English. The first chapter gives a brief overview over the methods and theories used.
In the second chapter the decline of object topicalization in the history of English is presented. The reason is neither a general tendency of English word order to become more rigid (topicalization stayed grammatical), nor a loss of pragmatic environments in which topicalization was felicitous (the environments stayed the same). By closer look we see that only sentences with full noun subjects are affected. The interpretation pursued in the thesis is that the loss of the V2 word order option led to situations in which topicalization would easily lead to the juxtaposition of focused element (as in ' beans, John likes, but peas, Mary likes'). Since this situation conflicts with the Clash Avoidance Requirement, language users chose not to topicalize in such cases.
Chapter 3 shows experimental evidence for the Clash Avoidance Requirement: In both English and German the participants avoided use of constructions violating the Clash Avoidance Requirement. If forced, they inserted clearly measurable pauses between the clashing accents. As a consequence of these findings, the proper treatment of metrical prominence and focal emphasis--focal emphasis understood as emphasis on an element in narrow focus--in the framework of Metrical Stress Theory is discussed. The Clash Avoidance Requirement appears here as essential condition on the relevant grid construction rules.
The fourth chapter investigates topicalization and the Clash Avoidance Requirement in Old English. Among sentences with topicalization, the variation of V2 and V3 sentences is shown not to be strictly governed by the kind of subject--pronoun subject leading to V3, lexical NP subject to V2--but to be sensitive to the information-structural function of both topicalized element and subject. We detect a clear correlation between V2 and focus on either the subject or the topicalized element which supports the theory of a prosodic motivation for the Middle English decline presented in chapter 2.
