FALLACIES OF SIMPLE INSPECTION. 535 



efficacy in calculous and cravelly disorders ; for a similar reason, the roots 

 of the Saxifraga granulata (white saxifrage) gained reputation in the cure 

 of the same disease; and the Euphrasia (eye-bright) acquired fame, as an 

 application in complaints of the eye, because it exhibits a black spot in its 

 corolla resembling the pupih The blood-stone, the Heliotropium of the 

 ancients, from the occasional small specks or points of a blood-red color 

 exhibited on its green surface, is even at this very day employed in many 

 parts of England and Scotland to stop a bleeding from the nose ; and net- 

 tle tea continues a popular remedy for the cure of Urticaria. It is also 

 asserted that some substances bear the signatures of the humors, as the 

 petals of the red rose that of the blood, and the roots of rhubarb and the 

 flowers of saffron that of the bile." 



The early speculations respecting the chemical composition of bodies 

 were rendered abortive by no circumstance more than by their invariably 

 taking for granted that the properties of the elements must resemble those 

 of the compounds which were formed from them. 



To descend to more modern instances ; it was long thought, and was 

 stoutly maintained by the Cartesians and even by Leibnitz against the 

 Newtonian system (nor did Newton himself, as M^e have seen, contest the 

 assumption, but eluded it by an arbitrary hypothesis), that nothing (of a 

 physical nature at least) could account for motion, except previous motion; 

 the impulse or impact of some other body. It was very long before the 

 scientific world could prevail upon itself to admit attraction and repulsion 

 {i. e., spontaneous tendencies of particles to approach or recede from one 

 another) as \iltimate laws, no more requiring to be accounted for than 

 impulse itself, if indeed the latter were not, in truth, resolvable into the 

 former. From the same source arose the innumerable hypotheses devised 

 to explain those classes of motion which appeared more mysterious than 

 others because there was no obvious mode of attributing them to impulse, 

 as for example the voluntary motions of the human body. Such were the 

 interminable systems of vibrations propagated along the nerves, or animal 

 spirits rushing up and down between the muscles and the brain ; which, if 

 the facts could have been proved, would have been an important addition 

 to our knowledge of physiological laws ; but the mere invention, or arbi- 

 trary supposition of them, could not unless by the strongest delusion be 

 supposed to render the phenomena of animal life more comprehensible, or 

 less mysterious. Nothing, however, seemed satisfactor}-, but to make out 

 that motion was caused by motion ; by something like itself. If it Avas 

 not one kind of motion, it must be another. In like manner it was sup- 

 posed that the physical qualities of objects must arise from some similar 

 quality, or perhaps only some quality bearing the same name, in the parti- 

 cles or atoms of which the objects were composed; that a sharp taste, for 

 example, must arise from sharp particles. And reversing the inference, the 

 effects produced by a phenomenon must, it was supposed, resemble in their 

 physical attributes the phenomenon itself. The influences of the planets 

 were supposed to be analogous to their visible peculiarities : Mars, being of 

 a red color, portended fire and slaughter ; and the like. 



Passing from physics to metaphysics, we may notice among the most re- 

 markable fruits of this a priori fallacy two closely analogous theories, em- 

 ployed in ancient and modern times to bridge over the cliasm between the 

 world of mind and that of matter ; the sjjecies sensibiles of the Epicureans, 

 and the modern doctrine of perception by means of ideas. These theories 

 are indeed, probably, indebted for their existence not solely to the fallacy in 



