"To conceive of such an entity we must imagine a material that is more evanescent than any known gas, even in its most diffused condition. It must combine the solidity of the most perfect conductor of heat (exceeding any known body in this respect to an infinite degree), with the transparency of an absolute vacuum. It must neither create friction by contact with any substance, nor possess attraction for matter; must neither possess weight (and yet carry the force that produces weight), nor respond to the influence of any chemical agent, or exhibit itself to any optical instrument. It must be invisible, and yet carry the force that produces the sensation of sight. It must be of such a nature that it can not, according to our philosophy, affect the corpuscles of earthly substances while permeating them without contact or friction, and yet, as a scientific incongruity, it must act so readily on physical bodies as to convey to the material eye the sensation of sight, and from the sun to creatures on distant planets it must carry the heat force, thus giving rise to the sensation of warmth. Through this medium, yet without sensible contact with it, worlds must move, and planetary systems revolve, cutting and piercing it in every direction, without loss of momentum. And yet, as I have said, this ether must be in such close contact as to convey to them the essence that warms the universe, lights the universe, and must supply the attractive bonds that hold the stellar worlds in position. A nothing in itself, so far as man's senses indicate, the ether of space must be denser than iridium, more mobile than any known liquid, and stronger than the finest steel."
"I can not conceive of such an entity," I replied.
"No; neither can any man, for the theory is irrational, and can not be supported by comparison with laws known to man, but the conception is nevertheless a primary necessity in scientific study. Can man, by any rational theory, combine a vacuum and a substance, and create a result that is neither material nor vacuity, neither something nor nothing, and yet an intensified all; being more attenuated than the most perfect of known vacuums, and a conductor better than the densest metal? This we do when we attempt to describe the scientists' all-pervading ether of space, and to account for its influence on matter. This hypothetical ether is, for want of a better theory of causes, as supreme in philosophy to-day as the alkahest of the talented old alchemist Van Helmont was in former times, a universal spirit that exists in conception, and yet does not exist in perception, and of which modern science knows as little as its speculative promulgator, Aristotle, did. We who pride ourselves on our exact science, smile at some of Aristotle's statements in other directions, for science has disproved them, and yet necessity forces us to accept this illogical ether speculation, which is, perhaps, the most unreasonable of all theories. Did not this Greek philosopher also gravely assert that the lion has but one vertebra in his neck; that the breath of man enters the heart; that the back of the head is empty, and that man has but eight ribs?"
"Aristotle must have been a careless observer," I said.
"Yes," he answered; "it would seem so, and science, to-day, bases its teachings concerning the passage of all forces from planet to planet, and sun to sun, on dicta such as I have cited, and no more reasonable in applied experiment."
"And I have been referred to you as a conscientious scientific teacher," I said; "why do you speak so facetiously?"
"I am well enough versed in what we call science, to have no fear of injuring the cause by telling the truth, and you asked a direct question. If your questions carry you farther in the direction of force studies, accept at once, that, of the intrinsic constitution of force itself, nothing is known. Heat, light, magnetism, electricity, galvanism (until recently known as imponderable bodies) are now considered as modifications of force; but, in my opinion, the time will come when they will be known as disturbances."
"Disturbances of what?"
"I do not know precisely; but of something that lies behind them all, perhaps creates them all, but yet is in essence unknown to men."
"Give me a clearer idea of your meaning."