800 THE POPULAR SCIENCE MONTHLY. 



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 thei'e may be 

 many ways Science, as yet, knows nothing of, by which w r e 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 hydro- 

 gen, by which, in accordance with the most ordinary natural laws, you 

 would not only rise to the ceiling and float there in gitasi-angeYic post- 

 ure, 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 inextinguish- 

 able 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 activi- 

 ties 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 mainte- 

 nance 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 jmalw (final cause) manifested in the last set of 

 phenomena, the causa materialis (material cause) and form alls (form- 

 al) 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- 



