724 THE POPULAR SCIENCE MONTHLY. 



which is now certainty having once been assumption. When Co- 

 pernicus divined that the planets revolve around the sun ; when 

 Kepler suggested that the planetary orbits are ellipses ; when New- 

 ton proposed the law of gravitation, and, later, the identity of gravi- 

 tation with the central force of the solar system ; when Huygens 

 conjectured that light is propagated by undulations ; when Harvey, in 

 the profession of which Dr. Beale is an ornament, supposed that the 

 blood flows from the left side of the heart into the right through the 

 arteries and veins ; when Locke asserted that heat is motion ; when 

 Franklin assumed that lightning and electricity are one ; when Dalton 

 affirmed that elements combine in definite, reciprocal, and multiple 

 proportions ; when Leverrier announced the existence and position of 

 a planet outside the orbit of Uranus ; when Faraday conceived the 

 principle of definite electro-chemical decomposition they each and all 

 indulged in what were " prophetic assumptions,'" until in due time the 

 assumptions were proved and the prophecy accomplished. And so, 

 for the most part, with the rest. Wherever, indeed, there is an in- 

 quisitor of nature, whether observer or experimenter, there is likely to 

 stand behind him some hypothesis, more or less shifting, more or less 

 defined, more or less probable, which guides his inquiries and shapes 

 their results ; and what is generally true of the experimental sciences 

 is true in greater degree of the sciences in which experiment is impos- 

 sible or possible only within a narrow range, such as astronomy, biol- 

 ogy, psychology, sociology. The truth is, without "prophetic assump- 

 tions," science would need either omnipotent insight, to see through 

 every problem at once, or that omnipotent blindness which enables its 

 happy possessor to solve every problem, as Dr. Beale would solve the 

 problem of life, by referring it out of hand to some agency beyond the 

 bounds of human knowledge ; but, as science is endowed with neither, 

 it has, in general, no other course, certainly no better course, than to 

 proceed tentatively by " prophetic assumptions," careful only, though 

 rigorously careful, that these shall fulfill the acknowledged conditions 

 of a legitimate hypothesis. As for such " assumptions " as Di*. Beale's, 

 they are not "prophetic," it is true, but only because they forever re- 

 nounce the hope of explanation. Science rejects them, as we have 

 seen. 



Let us see whether or not the hypothesis of the evolution of living 

 from not-living matter encounters the same fate. 



To begin with, the hypothesis, it will not be denied, is verifiable, 

 for it assumes only a certain competency in the properties of matter, 

 which, if it exists, is capable of proof under possible conditions, and, 

 if it does not exist, is capable in like manner of disproof ; so that in 

 the end the assumption must lead to certainty or step down and out. 

 Such being the case, it fulfills the first condition of a legitimate hy- 

 pothesis. 



The hypothesis, in the next place, assumes no special cause, known 



