In the Finale we examine to what extent Causal Mechanism can be seen as a descendant of the original notion of mechanism developed in seventeenth century, by examining possible extensions of the seventeenth-century notion of mechanism and discussing whether they can be used to characterise mechanism as a concept-in-use. We identify two conditions that a biological explanation has to satisfy in order to count as mechanistic, both of which were central in Old Mechanism: the condition of intelligibility and the condition of the priority of the parts over the whole. We use these two conditions to distinguish between two notions of mechanism: a more narrow one that incorporates both the intelligibility condition and the condition of the priority of the parts and a broader one that incorporates only the intelligibility condition and is thus a weakened form of mechanism. We claim that an account of mechanism as a concept-in-use requires the weakened notion, which when viewed in terms of Causal Mechanism has nevertheless enough content so that it can be seen as a descendant of the original concept.

Chapter 1 examines the relationship between Old and New Mechanism and uses it to illuminate the relations between metaphysical and methodological conceptions of mechanism. This historical examination will directly motivate our new deflationary account of mechanism developed in the subsequent chapters. We start by focusing on the role of mechanistic explanation in seventeenth-century scientific practice, by discussing the views of René Descartes, Christiaan Huygens, Gottfried Wilhelm Leibniz and Robert Boyle, and the attempted mechanical explanations of gravity by Descartes and Ηuygens. We thereby illustrate how the metaphysics of Old Mechanism constrained scientific explanation. We then turn our attention to Isaac Newton’s critique of mechanism. The key point is that Newton introduced a new methodology that freed scientific explanation from the metaphysical constraints of the older mechanical philosophy. Last, we draw analogies between Newton’s critique of Old Mechanism and our critique of New Mechanism. The main point is that causal explanation in the sciences is legitimate even if we bracket the issue of the metaphysics of mechanisms.

The Introduction recounts the main aspects of the recent revival of the mechanical philosophy and outlines the main theses of the book (i.e., Causal Mechanism and Methodological Mechanism). It presents briefly the case for understanding mechanism as a methodological concept, introduces the main concepts and distinctions that will be discussed in the book, provides an outline of the central arguments and presents a summary of the chapters.