THE DEDUCTIVE METHOD, 2G5 



beings, never could have been a matter of any doubt, however imper- 

 fe<'tly it may have been known either by what laWs those impressions 

 and actions are governed, or to what social consi;quences their laws 

 naturally lead. Neither, again, after physical science had attained a 

 certain development, coidd there be any real doubt where to look for 

 the laws on which the phenomena of life dejiend, since they must be 

 the mechanical and chemical laws of the solid and fluid sul>stances 

 composing the orgaiiized body and the medium in which it subsists, 

 together with the peculiar vital laws of the diflcrent tissues constituting 

 the organic structure. In other cases, really ftir more simple than 

 these, it was much less. obvious in what quarter the causes were to be 

 lookfd for : as in the great case of the celestial phenomena. Until, 

 by comi)ining the laws of certain causes, it ^vtl3 found that those laws 

 explained all the facts which experience had proved concerning the 

 heavenly motions,, and led to predictions which it always verified, 

 mankind never knew that those 7ccrc the causes. But whether we 

 are able to put the question before or not until after we have become 

 capable of answering it, in either case it must be answered ; the laws 

 of the different causes must be ascertained, before we can proceed to 

 deduce from them tjic conditions of the effect. 



The mode of ascertaining these laws neither is, nor can be, any 

 other than the fourfold method of experimental inquiry, already dis- 

 cussed. A few remarks on the application of that method to cases of 

 the Composition of Causes, are all that is requisite. 



It is obvious that we cannot expect to find the law of a tendency, 

 by an induction from cases in which the tendency is counteracted. 

 The laws of motion could never have been brought to light from the 

 observation of bodies kept at rest by the equilibrium of opposing 

 fotces. Even where the tendency is not, in the ordinary sense of the 

 word, counteracted, but only modified, by having its effects comjiounded 

 with the effects arising from some other tendency or tendencies, we 

 are still in an imfavorable position for tracing by means of such cases, 

 the law -of the tendency itself It would have been difficult to dis- 

 cover the law that every body in motion tends to continue moving in a 

 straight line, by an induction from instances in which the motion is 

 deflected into a curve, by being compounded with the effect of an 

 accelerating force. Notwithstanding the resources aftbrded in this 

 description of cases by the Method of Concomitant Variations, the 

 principles of a judicious experimentation prescribe that the law of each 

 of the tendencies should be studied, if possible, in cases in which that 

 tendency operates alone, or in combination with no agencies but those 

 of which the effect can, from previous knowledge, be calculated and 

 allowed fbr. 



AccordinglyT^n the cases, unhappily very numerous and important, 

 in which the caiises do not suffin- themselves to be separated and 

 observed apart, there is much difficulty in laying down, with due 

 certainty, the inductive foundation necessary to support the deductive 

 method. This difficulty is most conspicuous in the case of physiological 

 phenomena ; it being impossible to separate the different agencies 

 which collectively compose an organized body, without destroying the 

 very phenomena which it is our object to investigate : 



following life, in creatures we dissect, 



We lose it, in the nioment we detect. 



