gen into the "element" carbon, and their synthesis with the rest of the oxygen and hydrogen.
Theoretically, therefore, we can have no sort of objection to your miracle. And our reply to the levitators is just the same: Why should not your friend "levitate"? Fish are said to rise and sink in the water by altering the volume of an internal air-receptacle, and there may be many ways Science, as yet, knows nothing of, by which we who live at the bottom of an ocean of air may do the same thing. Dialectic gas and wind appear to be by no means wanting among you, and why should not long practice in pneumatic philosophy have resulted in the internal generation of something a thousand times rarer than hydrogen, by which, in accordance with the most ordinary natural laws, you would not only rise to the ceiling and float there in quasi-angelic posture, but perhaps, as one of your feminine adepts is said to have done, flit swifter than train or telegram to "still-vexed Bermoothes," and twit Ariel, if he happens to be there, for a sluggard? We have not the presumption to deny the possibility of anything you affirm—only, as our brethren are particular about evidence, do give us as much to go upon as may save us from being roared down by their inextinguishable laughter.
Enough of the realism which clings about "laws." There are plenty of other exemplifications of its vitality in modern science, but I will cite only one of them.
This is the conception of "vital force" which comes straight from the philosophy of Aristotle. It is a fundamental proposition of that philosophy that a natural object is composed of two constituents—the one its matter, conceived as inert or even, to a certain extent, opposed to orderly and purposive motion; the other its form, conceived as a quasi-spiritual something, containing or conditioning the actual activities of the body and the potentiality of its possible activities.
I am disposed to think that the prominence of this conception in Aristotle's theory of things arose from the circumstance that he was, to begin with and throughout his life, devoted to biological studies. In fact, it is a notion which must force itself upon the mind of any one who studies biological phenomena, without reference to general physics as they now stand. Everybody who observes the obvious phenomena of the development of a seed into a tree, or of an egg into an animal, will note that a relatively formless mass of matter gradually grows, takes a definite shape and structure, and finally begins to perform actions which contribute toward a certain end, namely, the maintenance of the individual in the first place, and of the species in the second. Starting from the axiom that every event has a cause, we have here the causa finalis (final cause) manifested in the last set of phenomena, the causa materialis (material cause) and formalis (formal) in the first, while the existence of a causa efficiens (efficient cause) within the seed or egg and its product, is a corollary from the phe-
