792 POPULAR SCIENCE MONTHLY. 



truths, we may be sure tliat furious controversy would have attended 

 the issue, and some way found to overthrow the demonstration. 

 That two and two make four would have been denied had any strong 

 emotion been excited against the proposition. " Men," said Whate- 

 ley, " are much more anxious to have truth on their side than to be 

 on the side of truth." And the danger is greater because we are 

 frequently not aware of the bias given by feeling. There are cases 

 in plenty where men more or less consciously and deliberately es- 

 pouse " sciences as one would," but there are many others in which 

 the emotional interference is insidious and obscure. " Numberless, 

 in short, are the ways, and sometimes imperceptible, in which the 

 feelings color and infect the understanding." 



These Idols of the Tribe are of course inherent in our intel- 

 lectual constitution, and are ineradicable. The simple considera- 

 tion that all knowledge is relative — that by no effort and under no 

 circumstances can we escape beyond the conditions and limitations 

 of our own minds — suffices to show that intelligence must ever mix 

 up its own nature with the nature of things, though this fact need 

 not make us doubt the validity of knowledge as is sometimes hastily 

 inferred. For the rest, clear recognition of these common obstacles 

 to thought should put us in the way of anticipating and withstand- 

 ing their more serious effects. In practice it must be our object 

 to maintain watchfulness and a careful skepticism; to test evidence 

 and check passion; to cultivate candor, flexibility, and alertness of 

 mind; to avoid loose generalizations; and to be ever ready to ac- 

 cept, revise, reject. Above all must we steadily resist the seduc- 

 tions of what is called common sense, and overcome that mental 

 inertness which too often leads us to drift unthinking along the cur- 

 rent of popular opinion.* 



But, in addition to errors arising from the common intellectual 

 nature of men, there are others, the sources of which are to be found 

 in the idiosyncrasies of the individual mind. These Bacon calls 

 Idols of the Cave ; f for every one, he says, " has a cave or den of his 

 own, which refracts and discolors the light of ISTature, owing either 

 to his own proper and peculiar nature ; or to his education and con- 

 versation with others; or to his reading of books, and the authority 

 of those whom he esteems and admires; or to the differences of im- 

 pressions, accordingly as they take place in a mind preoccupied and 

 predisposed, or in a mind indifferent and settled; and the like." 

 This summary is comprehensive enough to indicate the character 

 and point to some of the causes of individual aberrations of judg- 



* It is well to remember that if common sense had said the last word about the matter, 

 the Ptolemaic theory of the universe would still stand unshaken. 



f The metaphor is takeu from the opening of the seventh Iwok of Plato's Republic. 



