This book may be used as a textbook for the first or second year graduate student who is studying concurrently such topics as theory of complex analysis, classical mechanics, classical electrodynamics, and quantum mechanics.

In a textbook on statistical mechanics, it is common practice to deal with two important areas of the subject: mathematical formulation of the distribution laws of statistical mechanics, and demonstrations of the applicability of statistical mechanics.

The first area is more mathematical, and even philosophical, especially if we attempt to lay out the theoretical foundation of the approach to a thermodynamic equilibrium through a succession of irreversible processes. In this book, however, this area is treated rather routinely, just enough to make the book self-contained.

The second area covers the applications of statistical mechanics to many thermodynamic systems of interest in physics. Historically, statistical mechanics was regarded as the only method of theoretical physics which is capable of analyzing the thermodynamic behaviors of dilute gases; this system has a disordered structure and statistical analysis was regarded almost as a necessity.

Emphasis had been gradually shifted to the imperfect gases, to the gas–liquid condensation phenomenon, and then to the liquid state, the motivation being to be able to deal with correlation effects. Theories concerning rubber elasticity and high polymer physics were natural extensions of the trend. Along a somewhat separate track, starting with the free electron theory of metals, energy band theories of both metals and semiconductors, the Heisenberg–Ising theories of ferromagnetism, the Bloch–Bethe–Dyson theories of ferromagnetic spin waves, and eventually the Bardeen–Cooper–Schrieffer theory of super-conductivity, the so-called solid state physics, has made remarkable progress.