Thinking about Physics

The well known theoretical physicist and editor of the Journal of Mathematical Physics has written a handy book, with eight chapters devoted to the broader knowledge of and reflection about physical theories, notably quantum theory. After thinking about what is a physical theory, he addresses the problem of the state in quantum theory (a very central chapter of the book), the power of mathematics, the field - particle issue (the author pleads for the superiority of the field concept - the book is very indebted to Julian Schwinger's ideas), symmetry in physics, the problem of causality and probability, the five different arrows of time (from cause-effect ordering to the cosmological arrow), and finally turns to the presently quite often discussed relation of the quantum-mechanical description to reality. After one has learned that the author is not approaching the questions from a sharper historical point of view, and that he shares the prejudices of a mathematical physicist toward experiment, one thoroughly enjoys his elegant, competent and deep treatment. This reviewer wishes that every graduate student of physics should, at an early stage, read Newton's book (which could be done either at a stroke or piecewise) because it presents the essence of a great deal of modern physical theory in both a condensed and leisurely digestible form.