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The laser is treated as a thermodynamic machine where production of radiation is the result of entropy creating spontaneous flows of energy and polarization through the system. One of the laws of thermodynamics governing flows of extensive properties is the symmetry principle of Curie and Prigogine. It determines how much flows are coupled. Going back to the first principles of statistical mechanics and using aforementioned symmetry requirements, a set of alternative Bloch equations is derived. The impact of the new formulation on laser physics is developed. It leads to a set of new conclusions for spontaneous pulsating regimes, for the spectral line shape of coherent radiation, for saturation effects, etc.