This book addresses some of the problems of interpreting Schroedinger's mechanics - the most complete and explicit theory falling under the umbrella of quantum theory . The outlook is materialist ( realist ) and stresses the development of Schroedinger's mechanics from classical theories and its close connections with (particularly) the Hamilton-Jacobi theory. Emphasis is placed on the concepts and use of the modern objective (measure-theoretic) probability theory. The work is free from any mention of the bearing of Schroedinger's mechanics on God, his alleged mind or, indeed, minds at all. The author has taken the naive view that this mechanics is about the structure and dynamics of atomic and sub-atomic systems since he has been unable to trace any references to minds, consciousness or measurements in the foundations of the theory.