As I have worked on this book, I have often been struck by the audacity of its title. The phrase “the New Mechanical Philosophy” was not my own, but still, to appropriate the venerable tradition of mechanical philosophy, to call it new, and to add a definite article to boot—maybe that’s just too much. Nonetheless I have stuck with the title, and the project, because I think it reflects both the continuity with the history of science and its philosophy, and a sea change in philosophical thinking in the new century. Mechanical philosophy is as old as Democritus; it was a central theme in the scientific revolution; it has helped drive research and debates on the nature of life and the nature of mind. But the New Mechanical Philosophy is new in large part because it tracks changes in the way science is done. Over recent decades, the sciences have developed increasing, if still rudimentary, capacities to analyze complex and heterogeneous systems—cells, brains, ecosystems, economies, and so on. Whereas in earlier epochs many of the greatest scientific achievements have been to understand the basic building blocks—the laws of electricity and magnetism or the structure of the hydrogen atom—scientists are now able to greater and greater extents understand how these things are put together to make the universe we know. Mechanical philosophy is always about understanding how things are put together, so it is a philosophy for this time....