Note 84 — Chapter IV · THE WORLD OF THINGS—(1) SUBSTANCE, QUALITY, AND RELATION

This is just as true of the so-called primary qualities of things as of any others. Thus the mass and again the kinetic energy of a conservative material system are properly names for the way in which the system will behave under determinate conditions, not of modes of behaviour which are necessarily actually exhibited throughout its existence. The laws of motion, again, are statements of the same hypothetical kind about the way in which, as we believe, particles move if certain conditions are fulfilled. The doctrine according to which all events in the physical world are actual motions, rests on no more than a metaphysical blunder of a peculiarly barbarous kind. Cf. Stallo, Concepts and Theories of Modern Physics, chaps. 10-12.