In the late middle ages, chemistry was the science and technology closest to philosophy, the material realization of the method of analysis and synthesis. No longer. Contemporary philosophy is concerned with many sciences—physics, psychology, biology, linguistics, economics—but chemistry is not among them. Why not? Every discipline has particular problems with some philosophical coloring. Those in quantum theory are famous; those in psychology seem endless; those in biology and economics seem more sparse and esoteric. If, for whatever reason, one’s concern is the conceptual or theoretical problems of a particular science, there is no substitute for that science, and chemistry is just one among others. Certain sciences naturally touch on substantive areas of traditional philosophical concern: quantum theory on metaphysics, for example, psychology on the philosophy of mind, and economics and statistics on theories of rationality. In these cases, there is a special interest in particular sciences because they may reform prior philosophical theories or recast philosophical issues or, conversely, because philosophy may inform these subjects in fundamental ways. That is not true, in any obvious way, of chemistry. So what good, then, what special value, does chemistry offer contemporary philosophy of science? Typically philosophical problems, even problems in philosophy of science, are not confined to a particular science. For general problems—problems about representation, inference, discovery, explanation, realism, intertheoretic and interdisciplinary relations, and so on—what is needed are scientific illustrations that go to the heart of the matter without requiring specialized technical knowledge of the reader. The science needed for most philosophy is familiar, not esoteric, right in the middle of things, mature and diverse enough to illustrate a variety of fundamental issues. Almost uniquely, chemistry fits the description. In philosophy of science, too often an effort gains in weight and seriousness merely because it requires mastery of an intricate and arcane subject, regardless of the philosophical interest of what it says. Yet, surely, there is something contrived, even phony, in illustrating a philosophical point with a discussion of the top quark if the point could be shown as well with a discussion of the ideal gas law.