Quantum mechanics is one of the most fascinating， and at the same time most controversial， branches of contemporary science. Disputes have accompanied this science since its birth and have not ceased to this day. What is the sense of a probability interpretation of a physical phenomenon? Which approach to a quantum field theory is more consistent? How must we comprehend a quantum world? This book，leaving aside the search for spiritual content and answers to these questions， allows one to deeply contemplate some ideas and methods that are seldom met in the contemporary literature. Instead of widespread recipes of mathematical physics based on the solutions of integro-differential equations， we prefer logical and partly intuitional derivations of noncommutative algebra. The reader， having become armed with the necessary knowledge and skills from classical physics and symbolic mathematics， can thus directly penetrate the abstract world of quantum mechanics.
　　For exactly solvable models， we develop the method of factorization. This method， leaning primarily on Green's formalism， is applied for consideration of simple problems in the theory of vibrations and the relativistic theory of an electron. For more complicated problems， mainly related to the physics of various effects of anharmonicity， we develop the method of polynomials of quantum numbers， which enables one to systematize the calculations according to the perturbation theory. Regarding the quantum field theory and the calculation of observable radiative corrections， we rely entirely on Dirac's ideas， not on -at present-the pervasive rules of operation with a scattering matrix. Dirac's theory， possessing a proper elegance， is built on the equations of motion and is suitable for a first acquaintance with the principal problems of quantum electrodynamics， a matter of belief that remains open.
　　The author respectfully expresses his gratitude to John Ogilvie， who read the manuscript and made valuable comments. This book addresses a wide readership with serious enthusiasm about theoretical physics.