328 INDUCTION. 



not those in which there is any practical object in view. The experiments 

 are best tried, not in a state of disease, which is essentially a changeable 

 state, but in the condition of health, comparatively a fixed state. In the 

 one, unusual agencies are at work, the results of which we have no means 

 of predicting: in the other, the course of the accustomed physiological 

 phenomena would, it may generally be presumed, remain undisturbed, were 

 it not for the disturbing cause which we introduce. 



Such, with the occasional aid of the Method of Concomitant Variations 

 (the latter not less encumbered than the more elementary methods by the 

 peculiar difficulties of the subject), are our inductive resources for ascer- 

 taining the laws of the causes considered separately, when we have it not 

 in our power to make trial of them in a state of actual separation. The 

 insufficiency of these resources is so glaring, that no one can be surprised 

 at the backward state of the science of physiology; in which indeed our 

 knowledge of causes is so imperfect, that we can neither explain, nor could 

 without specific experience have predicted, many of the facts which are 

 certified to us by the most ordinary observation. Fortunately, we axe 

 much better informed as to the empirical laws of the phenomena, that is, 

 the uniformities respecting which we can not yet decide whether they are 

 cases of causation, or mere results of it. Not only has the order in which 

 the facts of organization and life successively manifest themselves, from 

 the first germ of existence to death, been found to be uniform, and very 

 accurately ascertainable ; but, by a great application of the Method of 

 Concomitant Variations to the entire facts of 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 com- 

 mon 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 description, 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 obtain- 

 ed by an induction from comparatively simple instances, or, at the worst, 

 by deduction from the laws of simpler causes, so obtained. By simple in- 

 stances are meant, of course, those in which the action of each cause was 

 not intermixed or interfered with, or not to any great extent, by other 

 causes whose laws were unknown. And only when the induction which 

 furnished the premises to the Deductive method rested on such instances 

 has the application of such a method to the ascertainment of the laws of a 

 complex effect, been attended with brilliant results. 



§ 2. When the laws of the causes have been ascei'tained, and the first 

 stage of the great logical operation now under discussion satisfactorily ac- 

 complished, the second part follows ; that of determining from the laws of 

 the causes what effect any given combination of those causes will pi'oduce. 

 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 

 o'xtend 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 



