470 FALLACIES. 



speculative science was missed from an undue contempt of manual 

 operations, the false speculative views thus engendered gave in their 

 turn a false direction to such practical and mechanical aims as were 

 still suflered to exist. The assumption universal among the ancients, 

 and in the middle ages, that there were principles of heat and cold, 

 dryness and moisture, &c., led directly to a belief in alchemy ; in a 

 transmutation of substances, a change fiom one Kind into another. 

 "Why should it not be possible to make gold 1 Each of the charac- 

 teristic properties of gold had its forma, its essence, its set of condi- 

 tions, which if we could discover, and learn how to realize, we could 

 superinduce that particular property upon any other substance, upon 

 wood, or iron, or hme, or clay. If, then, we could effect this with 

 respect to every one of the essential properties of the precious metals, 

 we should have converted the other substance into gold. Nor did this, 

 if once the premisses were granted, appear to transcend the real pow- 

 ers of man. For daily experience showed that almost every one of 

 the distinctive sensible properties of any object, its consistence, its 

 color, its taste, its smell, its shape, admitted of being totally changed 

 by fire, or water, or some other chemical agent. The fonnce of all 

 those qualities seeming, therefore, to be within human power either to 

 produce or to annihilate, not only did the transmutation of substances 

 appear absti'actedly possible, but the employment of the power, at oui* 

 choice, for practical ends, seemed by no means hopeless. 



A prejudice universal in the ancient world, and from which even 

 Bacon was so far fi-om being free, that it pen'aded and vitiated the 

 whole practical part of his system of logic, may with good reason be 

 ranked high in the order of Fallacies of which we are now ti-eating. 



§ 8. There remains one a priori fallacy or natural prejudice, the 

 most deeply-rooted, perhaps, of all which we have enumei-ated : one 

 which not only reigned supreme in the ancient world, but still possesses 

 almost undisputed dominion over many of the most cultivated minds ; 

 and some of the most remarkable of the numerous instances by which 

 I shall think it necessary to exemplify it, will be taken from the writings 

 of recent philosophers. This is, that the conditions of a phenomenon 

 must, or at least probably wnll, resemble the phenomenon itself. 



Conformably to what we have before remarked to be of frequent 

 occurrence, this fallacy might without much impropriety have been 

 placed in a different class, among Fallacies of Generalization : for 

 experience doe-s afford a certain degi'ee of countenance to the assump- 

 tion. The cause does, in very many cases, resemble its effect ; like 

 produces like. Many phenomena have a direct tendency to pei-jietuate 

 their own existence, or to give rise to other phenomena similar to them- 

 selves. Not to mention forms actually moulded upon one another, as 

 impressions on wax and the like, in which the closest resemblance 

 between the effect and its cause is the very law of the phenomenon ; 

 all motion tends to continue itself, with its own velocity, and in its own 

 original direction ; and the motion of one body tends to set others in 

 motion, which is indeed the most common of the modes in which the 

 motions of bodies originate. We need scarcely refer to contagion, 

 fermentation, and the like ; or to the production of effects by the 

 growth or expansion of a germ or i-udiraent resembling on a smaller 

 scale the completed phenomenon— as in the growth of a plant or animal 



