Analytic philosophers once pantomimed physics: they tried to understand the world by breaking it down into the smallest possible bits. Thinkers from the Darwinian sciences now pose alternatives to this simplistic reductionism. In this intellectual tour--essays spanning thirty years--William Wimsatt argues that scientists seek to atomize phenomena only when necessary in the search to understand how entities, events, and processes articulate at different levels. Evolution forms the natural world not as Laplace's all-seeing demon but as a backwoods mechanic fixing and re-fashioning machines out of whatever is at hand. W. V. Quine's lost search for a "desert ontology" leads instead to Wimsatt's walk through a tropical rain forest. This book offers a philosophy for error-prone humans trying to understand messy systems in the real world. Against eliminative reductionism, Wimsatt pits new perspectives to deal with emerging natural and social complexities. He argues that our philosophy should be rooted in heuristics and models that work in practice, not only in principle. He demonstrates how to do this with an analysis of the strengths, the limits, and a recalibration of our reductionistic and analytic methodologies. Our aims are changed and our philosophy is transfigured in the process.