" One key characteristic of structure is its richness. To illustrate, recall the comparison that John Rawls drew between checkers and chess when he was describing the Aristotelian principle (see page 386). Both games are played on a board with 64 squares, but they have different structures. Checkers has one kind of piece, while chess has six different kinds of pieces. The movement of any checker piece is restricted to a single square per turn unless it is capturing, while movement in chess is different for each piece. In checkers, the goal is to capture all the opponents’ pieces. In chess, the goal is to trap one particular piece. The structure of chess is objectively richer than the structure of checkers. It is no coincidence that chess has thousands of books written about tactics and strategy for every aspect of the game while checkers has a fraction of that number. The nature of accomplishment in checkers and chess is also objectively different, as reflected in their relative places in Western culture.[1] I measure the richness of a structure by three aspects: principles, craft, and tools. The scientific method offers convenient examples. Conceptually, a scientific experiment proceeds according to principles such as replicability, falsifiability, and the role of the hypothesis that apply across different scientific disciplines. The actual conduct of a classic scientific experiment involves craft—the generation of a hypothesis to be tested or a topic to be explored, the creation of the methods for doing so, and meticulous observance of protocols and procedures during the actual work. The details of craft differ not only across disciplines but within disciplines. They also have a family resemblance, in the sense that a meticulous scientist behaves in ways that are recognizable to scientists in every field—“meticulous” being one of the defining characteristics of craft practiced at a high level. Tools play a double role. Sometimes they are created in direct response to needs generated by principles and craft—accurate thermometers are an example—but at least as often, a tool turns out to have unanticipated uses that alter both principles and craft, independently expanding the realm of things a discipline can achieve. An example is the invention of the diffraction grating to study spectra of light, which 40 years later turned out to enable astronomers to study the composition of the stars. "

― Charles Murray , Human Accomplishment: The Pursuit of Excellence in the Arts and Sciences, 800 B.C. to 1950