12 THE SCIENCE OF LOGIC 



Moreover, it is by careful separation of a problem or subject 

 into its various parts and details that we are enabled to distin 

 guish betweeen the accidental and the essential, and to avoid 

 being misled by superficial resemblances and seeming connexions. 

 Habit, association, familiarity, are apt to lead us astray. We 

 very easily mistake invariable sequence for causality, and ap 

 parent reasons for real ones. 1 The principal sources and classes 

 of such mistakes will be enumerated in the sections on Fallacies. 



III. While, on the one hand, we must never accept anything as 

 true which we do not clearly know to be so, on the other hand, we 

 must not expect the same degree of certitude, or the same cogency of 

 evidence, in all the sciences. Disregard of the second portion of 

 this rule has led many, especially in modern times, into scepticism, 

 i.e. doubt about the capacity of the human mind to attain to 

 certitude about anything. Taking too narrow a view of &quot; science,&quot; 

 they expect cogent evidence in the concrete subject-matter of the 

 human sciences social, economic, and ethical evidence which, 

 of their very nature, these sciences cannot be expected to yield.- 

 And when it is not forthcoming they drift into scepticism. One 

 would imagine that St. Thomas Aquinas was writing for the 

 twentieth century, rather than the thirteenth, when he penned these 

 sentences : &quot; There are some who will not receive anything that 

 is told them unless it is mathematically proved. This is usual 

 with those who have had a mathematical training, because custom 

 is second nature. But it may be also due to the possession of a 

 strong imagination, combined with an undeveloped judicial faculty. 

 Others there are who will not receive anything unless there is 

 put before them some illustration of it that can strike their senses. 

 This, too, results either from habit, or from the predominance of 

 the influence exerted over them by their senses, or from want of 

 intellectual discrimination. . . . Others, however, there are who 



1 &quot; An Englishman resident in some city in South America sees united in the 

 inhabitants a profession of the Catholic religion, a great laxity of morals, and an 

 absence of all energy, fortitude or perseverance. Neglecting our rule, he comes to 

 the conclusion that there is a necessary connexion between Catholicism and the 

 vices around him. . . . Or, again, we may have observed in the newspapers that a 

 larger number of persons lose their lives by drowning on a Sunday than on any other 

 day. On this fact the Scotch Presbyterian makes the remark that it can only be 

 explained by the anger of God with all who take their pleasure on His Holy day : 

 quite overlooking the circumstance that it is on Sunday that a great number ot 

 excursionists of the middle and lower classes, who are unskilled in the use of boats 

 and can rarely swim, take their pleasure on the water.&quot; CLARKE, Logic, pp. 469, 

 470. 



2 Cf. JOSEPH, Logic, p. 489. 



