590 LOGIC OF THE MORAL SCIENCES. 



specify, are generally either plain to common observation or speed- 

 ily learnt from practice, rules may be safely acted upon by persons 

 who know nothing more than the rule. But in the complicated affairs 

 of life, and still more in those of states and societies, rules cannot be 

 relied on, without constantly refen'ing back to the scientific laws on 

 which they are founded. To know what are the practical contingen- 

 cies which require a modification of the rule, or which are altogether 

 exceptions to it, is to know what combinations of circumstances would 

 interfere with, or entirely counteract, the consequences of those laws : 

 and this can only be leanit by a reference to the theoretical grounds 

 of the rule. 



By a wise practitioner, therefore, rules of conduct will only be con- 

 sidered as provisional. Being made for the most numerous cases, or 

 for those of most ordinary occuiTence, they point out the manner in 

 which it will be least perilous to act, where time or means do not exist 

 for analyzing the actual circumstances of the case, or where for any 

 reason we cannot trust our judgment in estimating them. But they do 

 not at all supersede the propriety of going through (when circum- 

 stances permit) the scientific process requisite for framing a rule from 

 the data of the particular case before us. At the same time, the com- 

 mon rule may very properly serve as an admonition, that a certain 

 mode of action has been found by ourselves and others to succeed in 

 the cases of most common occurrence ; so that if it be unsuitable in the 

 case in hand, the reason of its being so will be likely to arise from 

 some unusual circumstance. 



§ 4. The error is therefore apparent, of those who would deduce the 

 line of conduct proper to particular cases, from supposed universal 

 practical maxims ; overlooking the necessity of constantly referring 

 back to the principles of the speculative science, in order to be sure of 

 attaining even the specific end which the rules have in view. How 

 much gieater still, then, must the error be, of setting up such unbend- 

 ing principles, not merely as universal rules for attaining a given end, 

 but as rules of conduct generally ; without regard to the possibility, 

 not only that some modifying cause may prevent the attainment of 

 the given end by the means which the rule prescribes, but that success 

 itself may conflict with some other end, which may possibly chance to 

 be more desirable. 



This is the habitual error of many of the political speculators whom 

 I have characterized as the geometrical school ; especially in France, 

 where ratiocination fi'om rules of practice forms the staple commodity 

 of journalism and political oratory; a misapprehension of the functions 

 of Deduction which has brought much discredit, in the estimation of 

 foreigners, upon the spirit of generalization so honorably characteristic 

 of the French mind. The common-places of politics, in France, are 

 large and sweeping practical maxims, from which as ultimate premisses 

 men reason downwards to particular applications, and this they call 

 being logical and consistent. For instance, they are perpetually ar- 

 guing that such and such a measure ought to be adopted, because it is 

 a consequence of the principle on which the form of government is 

 founded; of the principle of legitimacy, or the principle of the sove- 

 reignty of the people. To which it may be answered, that if these be 

 really practical principles, they must rest upon speculative grounds ; 



