FALLACIES OF SIMPLE INSPECTION, 523 



science of predictions, any association, though ever so faint or remote, by 

 which an object could be connected in however far-fetched a manner with 

 ideas either of prosperity or of danger and misfortune, was enough to de- 

 termine its being classed among good or evil omens. 



An example of rather a different kind from any of these, but falling un- 

 der the same principle, is the famous attempt on which so much labor and 

 ingenuity were expended by the alchemists, to make gold potable. The 

 motive to this was a conceit that potable gold could be no other than the 

 universal medicine ; and why gold ? Because it was so precious. It must 

 have all marvelous properties as a physical substance, because the mind 

 was already accustomed to marvel at it. 



From a similar feeling, " every substance," says Dr. Pa^'is,* " whose ori- 

 gin is involved in mystery, has at different times been eagerly applied to 

 the purposes of medicine. Not long since, one of those showers which are 

 now known to consist of the excrements of insects, fell in the north of 

 Italy ; the inhabitants regarded it as manna, or some supernatural panacea, 

 and they swallowed it with such avidity, that it was only by extreme ad- 

 dress that a small quantity Avas obtained for a chemical examination." 

 The superstition, in this instance, though doubtless partly of a religious 

 character, pi-obably in part also arose from the prejudice that a wonderful 

 thing must of course have wonderful properties. 



§ 3. The instances of a priori fallacy which we have hitherto cited be- 

 long to the class of vulgar errors, and do not now, nor in any but a rude 

 age ever could, iiujiose upon minds of any considerable attainments. But 

 those to which we are about to proceed, have been, and still are, all but 

 imiversally prevalent among thinkers. The same disposition to give ob- 

 jectivity to a law of the mind — to suppose that what is true of our ideas 

 of things must be time of the things themselves — exhibits itself in many of 

 the most accredited modes of philosophical investigation, both on physical 

 and on metaphysical subjects. In one of its most undisguised manifesta- 

 tions, it embodies itself in two maxims, which lay claim to axiomatic truth: 

 Things which we can not think of together, can not co-exist ; and Things 

 which we can not help thinking of together, must co-exist. I am not sure 

 that the maxims were ever expressed in these precise words, but the his- 

 tory both of philosophy and of popular opinions abounds with exemplifica- 

 tions of both forms of the doctrine. 



To begin with the latter of them: Things which we can not think of 

 except together, must exist together. This is assumed in the generally 

 received and accredited mode of reasoning which concludes that A must 

 accompany B in point of fact, because " it is involved in the idea." Such 

 thinkers do not reflect that the idea, being a result of abstraction, ought to 

 conform to the facts, and can not make the facts conform to it. The ar- 

 gument is at most admissible as an appeal to authority ; a surmise, that 

 what is now part of the idea, must, before it became so, have been found 

 by previous inquirers in the facts. Nevertheless, the philosopher who 

 more than all others made professions of rejecting authority, Descartes, 

 consti'ucted his system on this very basis. His favorite device for arriving 

 at truth, even in regard to outward things, was by looking into his own 

 mind for it. " Credidi me," says his celebrated maxim, " pro regula ge- 

 nerali sumere posse, omne id quod valde dilucid^ et distinct^ concipiebam, 



* Pharmacoloffia, Historical Introduction, p. 16. 



