LOGIC 



man, we propound propositions of co-existence. 

 These must be sought inductively, and proved by 

 the method of Agreement alone ; neither any of 

 the other Experimental Methods, nor the Deduc- 

 tive Method, is applicable. They are also peculiar 

 in not being amenable to any great comprehensive 

 generalisation, like the law of Universal Causa- 

 tion. We can never, therefore, have anything but 

 a cumulative proof of such coincidences that is, 

 a proof founded on a long series of confirmations, 

 with the entire absence of any exception. 



On the propositions of Similarity, Mathematics 

 are founded. For an affirmation of likeness, the 

 ultimate appeal must be to the senses, and per- 

 sonal experience. When we say, three and four 

 are equal to seven, we mean if the aggregate 

 named three is put along with the aggregate 

 named four the joint effect is the same as the 

 effect of the aggregate named seven. -The truths 

 of Geometry are derivative laws, where order in 

 place is one of the conditions or circumstances : 

 the ultimate laws being the laws of equality, or 

 the laws of mathematics in general. 



Before closing the subject of Induction, we may 

 advert to the grounds of the credibility or incredi- 

 bility of things presented to our belief for the 

 first time, and not proved by any independent 

 evidence of their own. When a fact is asserted 

 that we do not know to be true or false, but which 

 agrees with some great established induction, we 

 may say that it is credible, and needs only some 

 ordinary degree of testimony to make it actually 

 believed. Thus, if we are told that a great ava- 

 lanche broke away from a snowy mountain-height, 

 and acquired in its fall such force as to sweep 

 away everything that stood in its course, we reckon 

 the assertion credible, because it is merely an 

 instance of the working of a great natural power. 

 But when it is alleged that the spectres of dead 

 men come and tell secrets to the living, we call 

 the assertion incredible, because it contradicts all 

 the ascertained laws of things, and is not supported 

 by any one generalisation, or any of the usual 

 habits and proceedings of the world. We are so 

 accustomed to the fact that all nature's operations 

 are on the great scale, and are to be found re- 

 curring in many different circumstances, t;hat we 

 are entitled to look with suspicion upon any 

 isolated phenomenon. Such phenomenon is not 

 accounted worthy of being entertained until it is 

 shewn that there are more of the same character 

 to be found, or that it can be brought under some 

 of the previously established generalities of nature. 



FALLACIES, AND THE DISSECTION OF EVIDENCE. 



A few observations on the nature of the more 

 common fallacies will serve to extend the illustra- 

 tion of the principles and ideas that have already 

 been advanced. There are various classes of 

 fallacies, some of which may be enumerated as 

 follows : Misconceptions arising from the sug- 

 gestions of uncultivated human nature ; Fallacies 

 consisting of errors in ratiocination or deduction ; 

 Fallacies of bad induction, or violations of the 

 Experimental Methods ; Erroneous abstractions ; 

 and Fallacies arising from the defects and misuses 

 of the instrumentality of reasoning namely, 

 Language. 



i. We have sufficiently discussed the difficulty 

 that the human mind experiences in getting at 



nature's own point of view of the trains of causa- 

 tion which support the movements of the world. 

 The earliest impressions of outward things upon 

 the mind are very far indeed from the correct 

 impressions. In the first place, the appearances 

 presented to the senses are often the reverse of 

 the fact, as in the case of the heavenly motions. 

 In other cases, we are led to believe that things 

 are where they are not, as in the way that we are 

 misled by the refraction of light. Our feelings of 

 what goes on within ourselves often suggest an 

 exceedingly false view of the reality. For example, 

 the feeling we sometimes experience of a rush 

 along the nerves, gives us the belief of an actual 

 fluid motion taking place through the body. Our 

 feeling of weight or gravity renders it very difficult 

 to admit the notion of the antipodes, and of the 

 round form of the peopled earth. In the next 

 place, we have very strong instincts that pervert 

 our views of nature still further. We are very apt 

 to suppose that what we see and experience is the 

 true type and resemblance of what we do not see, 

 or that nature works everywhere exactly as with 

 us. Having no means of conceiving the unseen 

 except through the seen, and being ready to 

 believe that our conceptions of things correspond 

 to the things themselves, we are led to assume 

 that particular attitude of mind termed 'narrow- 

 ness of view.' Hence the discredit thrown upon 

 the statements of the early travellers respecting 

 remote countries, such as China, Abyssinia, and 

 aboriginal America. Another inveterate prepos- 

 session of human nature arises from the notions 

 that we form of force, power, and causation, aris- 

 ing from our own sense of effort, action, and 

 resistance. We are beset by the notion that the 

 activity and motions of the world are carried on 

 in exactly the same way that human beings go 

 through their various operations upon the outer 

 world. There is hardly any fallacy so completely 

 opposed to the truth of things as this. The active 

 agency of human beings, in moving matter from 

 place to place, always implies close contact with 

 the things acted on. The great peculiarity of 

 natural powers is their acting through distance, 

 or with intervals of empty space between the 

 agent and the thing acted on. Gravity extends 

 from heaven to earth, or through distances of 

 millions of miles. Heat and light are equally 

 remote in their influences. But in the first con- 

 sideration of these powers, the idea of close con- 

 tact, derived from human experience, was so 

 overpowering, that it was considered impossible 

 that these distant actions could be maintained 

 without some medium extending all the way from 

 one of the bodies to the other. This is the real 

 origin of the doctrines of an ethereal fluid pervad- 

 ing space, to exercise the powers of gravity, light, 

 and heat. But for the misleading influence of our 

 own sense of force, the facts would have been at 

 once assumed as the ordinances of nature, that 

 one body can gravitate to another through empty 

 space, and that one body can heat or light another 

 apparently in the same way ; and we should have 

 been content to ascertain what relations these 

 actions had to distance, to the nature of the 

 bodies, and to the other circumstances concerned 

 in producing the effect. The human race is not 

 yet emancipated from this fallacy. 



2. The fallacies of erroneous Ratiocination or 

 Deduction are what are treated of under the 



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