Energy, Entropy, and the Flow of Nature is an attempt to present the essential principles of energetics (thermodynamics) in a manner that is straight-forward, easy to understand, and logically consistent. It arises from the difficulties author Thomas F. Sherman has seen or experienced as a student of physical chemistry, as a teacher of biochemistry and biology, and as a colleague. The central message of the book is that all natural change can be understood as a flow across a gradient, and that part of the effect of every flow is to diminish its own gradient. The book's mission is to build understanding of the central concepts, and with understanding, a degree of confidence in going forth into the many directions that the study of energy opens up. The laws of energy and entropy can indeed, in their applications, become a very complicated subject involving multivariable calculus, differential equations, and challenging problems and calculations. The fundamentals of energetics should be very straightforward, requiring relatively little mathematics—and it is the fundamentals that this book focuses on.