In Chapter 4 we build on the discussion in Chapter 3 in order to argue that understanding mechanisms in the Causal Mechanism sense is all that is needed in order to understand biological practice. We clarify the main commitments of our view by presenting three theses that together constitute Causal Mechanism: (1) Mechanisms are to be identified with causal pathways; (2) causal relations among the components of a pathway are to be viewed in terms of difference-making; and (3) Causal Mechanism is metaphysically agnostic. A key point is that, in contrast to mechanistic theories of causation, for Causal Mechanism causation as difference-making is conceptually prior to the notion of a mechanism. We examine in some detail the discovery of the mechanism of scurvy in order to argue that difference-making is what matters in practice. We then turn to the main inflationary accounts of mechanism and contrast them with our deflationary view and its metaphysical agnosticism. We argue that Causal Mechanism offers a general characterisation of mechanism as a concept-in-use in the life sciences that is deflationary and thin, but still methodologically important.