The basic idea behind this volume is to probe the nature of grammaticalization. Its contributions focus on the following questions: (i) In how far can grammaticalization be considered a universal diachronic process or mechanism of change and in how far is it conditioned by synchronic factors? (ii) What is the role of the speaker in grammaticalization? (iii) Does grammaticalization itself provide a cause for change or is it an epiphenomenon, i.e. a conglomeration of causal factors/mechanisms which elsewhere occur independently? (iv) If it is epiphenominal, how do we explain that similar pathways so often occur in known cases of grammaticalization? (v) Is grammaticalization unidirectional? (vi) What is the nature of the parameters guiding grammaticalization? The overall aim of the book is to enrich our understanding of what grammaticalization does or does not entail via detailed case studies in combination with theoretical and methodological discussions.