The book comprises a series of authors personal texts on various subjects in Theoretical Physics. Some are easy writings, like those on our worlds numbers, main physical principles, numerical computation, probabilities, general laws of motion. Others deal with old subjects, like celestial mechanics, particles scattering, fluids, many-body dynamics, the Thomas-Fermi atom, superfluidity, liquids. New insights are obtained from old problems, included in these Lectures, like the relation between quantization and the non-inertial motion, or the curved spaces, the connection between teleportation...