We try to show the necessity of accepting the fundamental continuity
hypothesis, which implies introduction of such new notions as integral parameters of a
medium and their densities. We also discuss a configuration of a body and its
deformation as well as methods of its description. The concepts of the Lagrangian and
Euler coordinates are considered.
Keywords: Causality principle, Conservation law, Continuity hypothesis,
Continuum, Current configuration, Deformation, Euler coordinates, Integral
parameter, Knudsen number, Lagrangian coordinates, Local parameter (density),
Reference configuration.
