This book comments briefly on the relation between general ideas about complexity and the particular hierarchic form of complexity with which the book is chiefly concerned. The thesis is that certain phenomena or entities are "artificial" in the sense that they are contingent to the goals or purposes of their designer. In other words, they could have been different had the goals been different (as opposed to natural phenomena which are necessarily evolved given natural laws). – Chapter 1 tackles the following issue: Since artifacts are contingent, how is a science of the artificial possible? How to study artifacts empirically? Chapter 4, on the other hand, deals with the notion of complexity. This is necessary because "artificiality and complexity are inextricably interwoven." M.-M. V.