The physicist who regards the ether as consisting of discrete particles not in bodily or actual contact, and at the same time finds himself logically compelled to reject this "mystical action at a distance," has no alternative but to accept the doctrine of Newton that the action of one particle of matter upon another is mediated by an agent which is not _material_. "If it be true that the conception of _force_ as the originator of motion in matter without bodily contact ... is essential to the right interpretation of phenomena; and if it be equally true, on the other hand, that its exertion makes itself manifest to our personal consciousness by that peculiar sensation of _effort_ which is not without its analogue in purely intellectual acts of the mind, it [_i. e._, force] comes not unnaturally to be regarded as affording a point of contact, a connecting link between these two great departments of being--between mind and matter--the one as the _originator_, the other as the _recipient_ of force."[282] There are distinguished physicists--as Helmholtz, Thomson, Challis, and Maxwell--who seek to escape the difficulties of action at a distance by the assumption that the ether is absolutely continuous (and therefore does not consist of atoms)--a perfectly homogeneous, incompressible, frictionless fluid which fills the universe. This fundamental presupposition as the basis of a physical theory of the universe necessitates the further assumption that "_motion is the very essence of what has been hitherto called matter_."[283] All quantitative and qualitative phenomena, all statical and dynamical phenomena, are due solely to varied modes of motion in the primordial fluid. "By various motions of the nature of eddies [ring-vortices], the qualities of matter--cohesion, elasticity, hardness, weight, mass, or other universal properties of matter--are given to small _portions_ of the fluid which constitute the _chemical atom_, and these, by modifications in their combinations, form, and motion, produce the accidental phenomena of _gross matter_.... On this view, gross matter would be merely an assemblage of _parts_ of the medium moving in a peculiar way, groups of ring-vortices having inertia.... The primary fluid by other motions transmits light, radiant heat, magnetism, and _gravitation_."[284]