Physicist Stephen M. Barr's lucid Student's Guide to Natural Science aims to give students an understanding, in broad outline, of the nature, history, and great ideas of natural science from ancient times to the present, with a primary focus on physics. Barr begins with the contributions of the ancient Greeks, in particular the two great ideas that reality can be understood by the systematic use of reason and that phenomena have natural explanations. He goes on to discuss, among other things, the medieval roots of the scientific revolution of the seventeenth century, the role played by religion in fostering the idea of a lawful natural order, and the major breakthroughs of modern physics, including how many newer "revolutionary" theories are in fact related to much older ones. Throughout this thoughtful guide, Barr draws his readers' attention to the larger themes and trends of scientific history, including the increasing unification  and "mathematization" of our view of the physical world that has resulted in the laws of nature appearing more and more as forming a single harmonious mathematical edifice.