merely a space without matter, in so far as it is a sum- total of several spaces, just as one may say of every geometrical figure, "it occupies a space" (it is extended); or even whether there he something in space necessitat- ing another movable to penetrate deeper into the same (attracting others); because, I say, by the conception of the occupying of a space, all this is undetermined; so, to fill a space is a closer definition of the conception to occupy a space.
Proposition 1.
Matter fills a space, not by its mere existence, but by a special moving force.
Demonstration.
The penetration into a space (in the moment of com- mencement this is called the endeavour to penetrate) is a motion. The resistance to motion is the cause of its diminution, and also its change into rest. Now nothing can be connected with any motion, as lessening or des- troying it but another motion of the same movable in the opposite direction (phoronomic proposition). Thus the resistance oifered by a matter in the space which it fills, to all impression of another [matter], is a cause of the motion of the latter in the opposite direction; but the cause of a motion is called moving force. Thus matter fills its space by moving force and not by its mere existence.
Observation.
Lambert and others called the property of matter, by which it fills a space, solidity (a rather ambiguous expres- sion), and maintained that we must assume it in every- thing which exists (substance), at le ist in the outer world of sense. According to their notions, the presence of something real in space, must carry with it this resistance by its very conception, in other words according to the principle of contradiction; and must exclude the co- existence of anything else, in the space of its presence. But the principle of contradiction does not preclude any matter from advancing, in order to penetrate into a space
