526 



FALLACIES. 



istam notionem ex aquH tantum, et 

 communibus et vulgaribus liquoribus, 

 absque ulla debita veriticatione, te- 

 mere abstractam esse." 



Bacon himself is not exempt from a 

 similar accusation when inquiring into 

 the nature of heat : where he occa- 

 sionally proceeds like one who, seek- 

 ing for the cause of hardness, after 

 examining that quality in iron, flint, 

 and diamond, should expect to find 

 that it is something which can be 

 traced also in hard water, a hard 

 knot, and a hard heart. 



The word Kivrjais in the Greek phi- 

 losophy, and the words Generation 

 and Corruption, both then and long 

 afterwards, denoted such a multitude 

 of heterogeneous phenomena, that any 

 attempt at philosophising in which 

 those words were used was almost as 

 necessarily abortive as if the word 

 hard had been taken to denote a class 

 including all the things mentioned 

 above. Kivrjais, for instance, which 

 properly signified motion, was taken 

 to denote not only all motion, but 

 even all change ; aXXoiioais being re- 

 cognised as one of the modes of 

 KivT^ais, The effect was, to connect 

 with every form of dWoiwais or 

 change, ideas drawn from motion in 

 the proper and literal sense, and 

 which had no real connection with 

 any other kind of Kiv-rjais than that. 

 Aristotle and Plato laboured under a 

 continual embarrassment from this 

 misuse of terms. But if we proceed 

 further in this direction we shall en- 

 croach upon the Fallacy of Ambiguity, 

 which belongs to a different class, the 

 last in order of our classification, Fal- 

 lacies of Confusion. 



CHAPTER VL 



FALLACIES OP RATIOCINATION. 



§ I. We have now, in our progress 

 through the classes of Fallacies, ar- 

 rived at those to which, in the com- 

 jjjQn books of logic, the appellation is 



in general exclusively appropriated ; 

 those which have their seat in the 

 ratiocinative or deductive part of the 

 investigation of truth. Of these fal- 

 lacies it is the less necessary for us 

 to insist at any length, as they have 

 been most satisfactorily treated in a 

 work familiar to almost all, in this 

 country at least, who feel any in^ 

 terest in these speculations. Arch- 

 bishop Whately's Logic. Against the 

 more obvious forms of this class of 

 fallacies, the rules of the syllogism 

 are a complete protection. Not (as 

 we have so often said) that ratiocina- 

 tion cannot be good unless it be in 

 the form of a syllogism ; but that, by 

 showing it in that form, we are sure 

 to discover if it be bad, or at least if 

 it contain any fallacy of this class. 



§ 2. Among Fallacies of Ratiocina- 

 tion, we ought perhaps to include the 

 errors committed in processes which 

 have the appearance only, not the 

 reality, of an inference from premises — 

 the fallacies connected with the con- 

 version and sequipollency of proposi- 

 tions. I believe errors of this de- 

 scription to be far more frequently 

 committed than is generally sup- 

 posed, or than their extreme obvious- 

 ness might seem to admit of. For 91 

 example, the simple conversion of an VI 

 universal affirmative proposition. All 

 A are B, therefore all B are A, I take 

 to be a very common form of error : 

 though committed, like many other 

 fallacies, oftener in the silence of 

 thought than in express words, for 

 it can scarcely be clearly enunciated 

 without being detected. And so with 

 another form of fallacy, not substanr 

 tially different from the preceding : 

 the erroneous conversion of an hypo- 

 thetical proposition. The proper con- 

 verse of an hypothetical proposition 

 is this : If the consequent be false, 

 the antecedent is false ; but this. If AM 

 the consequent be true, the ante- ■■ 

 cedent is true, by no means holds 

 good, but is an erior corresponding 

 to the simple conversion of an uni- 

 yers£<,l affirmative. Yet hardly auy- 



II 



