The original aim of this chapter was to present a synthesis of the geological evolution of the terranes of Scotland prior to their assembly into the current geography of the region. Given the differing hypotheses presented in the preceding four chapters, this chapter could as well concentrate on what is not known about Scotland’s geological evolution. There are too many unresolved big issues to be complacent about the progress that has been made since the third edition of this book was published in 1991. So, in attempting to synthesize the geology, pre-370Ma, perhaps the aim should also be to deconstruct the currently held views (as summarized in Chapter 1) in an attempt for better understanding. Chapters 3 to 6 were largely completed in 2001, but some important age dating papers have subsequently been published and these data are considered below.