This book is a labor of love aimed at helping students see the beauty and unity of physics. evolved from a second-year graduate course in quantum mechanics (QMII), in which I joked to my students that in one year we covered three or four books on different topics, each of which normally takes a year's course! While at times it seemed difficult to strike a satisfying balance between depth and breadth, at some point the material began to congeal into a collection of topics which I believed all graduate students in physical sciences wanted study before taking research-oriented specialty courses. Whereas much space in the book given to developing the needed tools, much is also given to developing new ideas about physics and nature.