512 INDUCTION. 



comparative anatomy and physiology, the characteristic organic 

 structure corresponding to each class of functions has been 

 determined with considerable precision. Whether these organic 

 conditions are the whole of the conditions, and in many cases 

 whether they are conditions at all, or mere collateral effects of 

 some common cause, we are quite ignorant : nor are we ever 

 likely to know, unless we could construct an organized body, 

 and try whether it would live. 



Under such disadvantages do we, in cases of this descrip- 

 tion, attempt the initial, or inductive step, in the application 

 of the Deductive Method to complex phenomena. But such, 

 fortunately, is not the common case. In general, the laws of 

 the causes on which the effect depends may be obtained by an 

 induction from comparatively simple instances, or, at the 

 worst, by deduction from the laws of simpler causes, so 

 obtained. By simple instances are meant, of course, those 

 in which the action of each cause was not intermixed or inter- 

 fered with, or not to any great extent, by other causes whose 

 laws were unknown. And only when the induction which fur- 

 nished the premises to the Deductive method rested on such 

 instances, has the application of such a method to the ascer- 

 tainment of the laws of a complex effect, been attended with 

 brilliant results. 



2. When the laws of the causes have been ascertained, 

 and the first stage of the great logical operation now under 

 discussion satisfactorily accomplished, the second part follows ; 

 that of determining from the laws of the causes, what effect 

 any given combination of those causes will produce. This is a 

 process of calculation, in the wider sense of the term ; and very 

 often involves processes of calculation in the narrowest sense. 

 It is a ratiocination ; and when our knowledge of the causes is 

 so perfect, as to extend to the exact numerical laws which 

 they observe in producing their effects, the ratiocination may 

 reckon among its premises the theorems of the science of 

 number, in the whole immense extent of that science. Not 

 only are the most advanced truths of mathematics often 

 required to enable us to compute an effect, the numerical law 



