610 THE POPULAR SCIENCE MONTHLY. 



question how we know these things. Can we know them, and do 

 we know them, by contemplating the necessities of the case ? or 

 must we have recourse to " inductions based on careful observa- 

 tion and experience " ? Before we make and enforce laws against 

 murder, ought we to inquire into the social welfare and individual 

 happiness in places where murder prevails, and observe whether 

 or not the welfare and happiness are greater in places where mur- 

 der is rare ? Shall robbery be allowed to go on until, by collecting 

 and tabulating the effects in countries where thieves predominate 

 and in countries where thieves are but few, we are shown by induc- 

 tion that prosperity is greater when each man is allowed to retain 

 that which he has earned ? And is it needful to prove by accu- 

 mulated evidence that breaches of contract impede production and 

 exchange, and those benefits to each and all which mutual depend- 

 ence achieves ? In the third place, these instances of actions which, 

 pushed to extremes, cause social dissolution, and which, in smaller 

 degrees, hinder social co-operation and its benefits, I give for the 

 purpose of asking what is their common trait. In each of such 

 actions we see aggression a carrying on of life in a way which di- 

 rectly interferes with the carrying on of another's life. The rela- 

 tion between effort and consequent benefit in one man, is either 

 destroyed altogether or partially broken by the doings of another 

 man. If it be admitted that life can be maintained only by certain 

 activities (the internal ones being universal, and the external ones 

 being universal for all but parasites and the immature), it must 

 be admitted that when like-natured beings are associated, the re- 

 quired activities must be mutually limited ; and that the highest 

 life can result only when the associated beings are so constituted 

 as severally to keep within the implied limits. The restrictions 

 stated thus generally, may obviously be developed into special 

 restrictions referring to this or that kind of conduct. These, then, 

 I hold are a priori truths which admit of being known by contem- 

 plation of the conditions axiomatic truths which bear to ethics a 

 relation analogous to that which the mathematical axioms bear to 

 the exact sciences. 



I do not mean that these axiomatic truths are cognizable by 

 all. For the apprehension of them, as for the apprehension of 

 simpler axioms, a certain mental growth and a certain mental dis- 

 cipline are needed. In the " Treatise on Natural Philosophy " by 

 Profs. Thomson and Tait, it is remarked that " physical axioms 

 are axiomatic to those only who have sufficient knowledge of the 

 action of physical causes to enable them to see at once their neces- 

 sary truth." Doubtless a fact and a significant fact. A plow-boy 

 can not form a conception of the axiom that action and reaction 

 are equal and opposite. In the first place he lacks a sufficiently 

 generalized idea of action has not united into one conception 



