Pro Levitate (a) ALERTNESS contra INERTNESS In the preceding chapter we gained a new insight into the relationship between mass and force. We have come to see that our concept of force is grounded on empirical observation in no less a degree than is usually assumed for our concept of number, or size, or position, provided we do not confine ourselves to non-stereoscopic, colourless vision for the forming of our scientific world-picture, but allow other senses to contribute to it. As to the concept mass, our discussion of the formula F=ma showed that force and mass, as they occur in it, are of identical nature, both having the quality of force. The factors F and m signify force in a different relationship to space (represented by the factor a). This latter fact now requires some further elucidation. In a science based on the Goethean method of contemplating the world of the senses, concepts such as 'mass in rest' and 'mass in motion' lack any scientific meaning (though for another reason than in the theory of Relativity). For in a science of this kind the universe - in the sense propounded lately by Professor Whitehead and others - appears as one integrated whole, whose parts must never be considered as independent entities unrelated to the whole. Seen thus, there is no mass in the universe of which one could say with truth that it is ever in a state of rest. Nor is there any condition of movement which could be rightly characterized by the attributes 'uniform' and 'straight line' in the sense of Newton's first law. This does not mean that such conditions never occur in our field of observation. But as such they have significance only in relation to our immediate surroundings as a system of reference. Even within such limits these conditions are not of a kind that would allow us to consider them as the basis of a scientific world-picture. For as such they occur naturally only as ultimate, never as primeval conditions. All masses are originally in a state of curvilinear movement whose rates change continuously. To picture a mass as being in a state of rest, or of uniform motion in a straight line, as the result of no force acting on it, and to picture it undergoing a change in the rate and direction of its motion as the result of some outer force working on it, is a sheer abstraction. In so far as mass appears in our field of observation as being in relative rest or motion of the kind described, this is always the effect of some secondary dynamic cause.