A venerable tradition in the metaphysics of science commends ontological reduction: the practice of analysis of theoretical entities into further and further proper parts, with the understanding that the original entity is nothing but the sum of these. This tradition implicitly subscribes to the principle that all the real action of the universe (also referred to as its "causation") happens at the smallest scales-at the scale of microphysics. A vast majority of metaphysicians and philosophers of science, covering a wide swath of the spectrum from reductionists to emergentists, defend this principle. It provides one pillar of the most prominent theory of science, to the effect that the sciences are organized in a hierarchy, according to the scales of measurement occupied by the phenomena they study. On this view, the fundamentality of a science is reckoned inversely to its position on that scale. This venerable tradition has been justly and vigorously countered-in physics, most notably: it is countered in quantum theory, in theories of radiation and superconduction, and most spectacularly in renormalization theories of the structure of matter. But these counters-and the profound revisions they prompt-lie just below the philosophical radar. This book illuminates these counters to the tradition principle, in order to assemble them in support of a vaster (and at its core Aristotelian) philosophical vision of sciences that are not organized within a hierarchy. In so doing, the book articulates the principle that the universe is active at absolutely all scales of measurement. This vision, as the book shows, is warranted by philosophical treatment of cardinal issues in the philosophy of science: fundamentality, causation, scientific innovation, dependence and independence, and the proprieties of explanation.