The Scottish Enlightenment is both a set of institutions and a set of ideas. As such they represent two differing facets of a complex whole. It is bad metaphysics to give one some sort of explanatory priority over the other – the argument that ‘luxury’ corrupts is just as ‘real’ as the number of diamond buckles for sale in the market. Given that the title of this book contains the word ‘idea’ then it is the latter set that will be the main focus. However, in acknowledgment (albeit in practice token) of complexity, this opening chapter provides, in Part I, an outline of the institutional setting. With respect to this setting, it needs always to be borne in mind that there is no necessary correspondence between what the historian can retrospectively identify as the ‘objective’ facts of the matter and what was subjectively apparent to those living in the time. Discounting as fanciful the possibility of mass self-deception, in this outline, I use ‘improvement’ as the principle of selection. This is a particular, documentable facet of the Scots' self-consciousness about their own society. Moreover, suitably reflecting the complex totality, ‘improvement’ exemplifies the linkage between the institutional and ideational dimensions of the Scottish Enlightenment; indeed, if less centrally, of the Enlightenment more generally. This wider picture is sketched in Part II and adumbrates some of the themes to be developed in subsequent chapters.