Historical references concerning the establishment of the conventional character of the concept of simultaneity of spatially separated events are cited in the article. It is shown that when the criteria for simultaneity admissible on the basis of cause-effect relations have been chosen, there appear in the general case anisotropic descriptions of the velocities of physical processes, which, owing to kinematic similitude, are impossible to distinguish from the isotropic description. It is noted that the theory constructed by Lorentz in his 1904 paper is essentially one of possible forms of presentation of the theory of relativity. The attempts to ``develop'' Lorentz's erroneous explanation of the relativistic effects are reviewed. The special theory of relativity is analyzed with allowance for the conventionality of the individual propositions of the traditional form of presentation of the theory. A preliminary analysis of the kinematics of physical phenomena for different reference frames in common space-time scales enabled us to establish the fact that the relativity principle is satisfied, owing to the appearance of a kinematic similitude for the corresponding processes, which proceed differently in different inertial coordinate systems. It is shown that the characteristics of the Lorentz transformations lie in just an expression for a universal difference between the velocities of propagation of physical processes in the direction of relative motion of the reference frames. The necessity of the universality requirement for the properties of motion, expressed in terms of the metric properties of space-time, is especially emphasized in the paper, and attention is drawn to a possible use of the old data on the metric of the physical space-time to uncover new properties of motion.