Matter is known to us only through its manifestations of Force: abstractits resistance mediately or immediately offered and there remains nothingbut empty extension. Yet, on the other hand, resistance is equally unthinkableapart from Matter -- apart from something extended. Not only are centresof force devoid of extension unimaginable, but we cannot imagine either extendedor unextended centres of force to attract and repel other such centres ata distance, without the intermediation of some kind of matter. The hypothesisof Newton, equally with that of Boscovich, is open to the charge that itsupposes one thing to act on another through empty space -- a suppositionwhich cannot be represented in thought. This charge is indeed met by introducinga hypothetical fluid existing among the atoms or centres. But the problemis not thus solved: it is simply shifted, and reappears when the constitutionof this fluid is inquired into. How impossible it is to elude the difficultyis best seen in the case of astronomical forces. The Sun gives us sensationsof light and heat; and we have ascertained that between the cause as existingin the Sun, and the effect as experienced on the Earth, a lapse of eightminutes occurs: whence unavoidably result in us the conceptions of both aforce and a motion. So that for assuming a luminiferous ether, there is thedefence, not only that the exercise of force through 92,000,000 of milesof absolute vacuum is inconceivable, but also that it is impossible to conceivemotion in the absence of something moved. Similarly in the case of gravitation.
Newton described himself as unable to think that the attraction of one bodyfor another at a distance, could be exerted in the absence of an interveningmedium. But now let us ask how much the forwarder we are if an interveningmedium be assumed. This ether whose undulations according to the receivedhypothesis constitute heat and light, and which is the vehicle of gravitation-- how is it constituted? We must regard it in the way that physicists usuallyregard it, as composed of atoms or molecules which attract and repel oneanother: infinitesimal it may be in comparison with those of ordinary matter,but still atoms or molecules. And remembering that this ether is imponderable,we are obliged to conclude that the ratio between the interspaces of theseatoms and the atoms themselves is immense. Hence we have to conceive theseinfinitesimal molecules acting on one another through relatively vast distances.
How is this conception easier than the other? We still have mentally. torepresent a body as acting where it is not, and in the absence of anythingby which its action may be transferred; and what matters it whether thistakes place on a large or a small scale? Thus we are obliged to concludethat matter, whether ponderable or imponderable, and whether aggregated orin its hypothetical units, acts on matter through absolutely vacant space;and yet this conclusion is unthinkable.
Another difficulty of conception, converse in nature but equally insurmountable,must be added. If, on the one hand, we cannot in thought see matter actingupon matter through vacant space; on the other hand, it is incomprehensiblethat the gravitation of one particle of matter towards another, and towardsall others, should be the same whether the intervening space is filled withmatter or not. I lift from the ground, and continue to hold, a pound weight.
Now, into the vacancy between it and the ground, is introduced a mass ofmatter of any kind whatever, in any state whatever; and the gravitation ofthe weight is entirely unaffected. Each individual of the infinity of particlescomposing the Earth acts on the pound in absolutely the same way, whateverintervenes, or if nothing intervenes. Through eight thousand miles of theEarth's substance, each molecule at the antipodes affects each molecule ofthe weight, in utter indifference to the fullness or emptiness of the spacebetween them. So that each portion of matter in its dealings with remoteportions, treats all intervening portions as though they did not exist; andyet, at the same time, it recognizes their existence with scrupulous exactnessin its direct dealings with them.
While then it is impossible to form any idea of Force in itself, it isequally impossible to comprehend its mode of exercise. §19. Turning now from the outer to the inner world, let us contemplate,not the agencies to which we ascribe our subjective modifications, but thesubjective modifications themselves. These constitute a series. Difficultas we find it distinctly to individualize them, it is nevertheless beyondquestion that our states of consciousness occur in succession.
Is this chain of states of consciousness infinite or finite? We cannotsay infinite; not only because we have indirectly reached the conclusionthat there was a period when it commenced, but also because all infinityis inconceivable -- an infinite series included. If we say finite we sayit inferentially; for we have no direct knowledge of either of its ends.
Go back in memory as far as we may, we are wholly unable to identify ourfirst states of consciousness. Similarly at the other extreme. We infer atermination to the series at a future time, but cannot directly know it;and we cannot really lay hold of that temporary termination reached at thepresent moment. For the state of consciousness recognized by us as our last,is not truly our last. That any mental affection may be known as one of theseries, it must be remembered -- represented in thought, not presented. Thetruly last state of consciousness is that which is passing in the very actof contemplating a state just past -- that in which we are thinking of theone before as the last. So that the proximate end of the change eludes us,as well as the remote end.
