438 INDUCTION. 



CHAPTER XXV. 



OP THE GROUNDS OF DISBELIEF. 



§ 1. The method of arriving at general truths, or general propositions 

 fit to be believed, and the nature of the evidence on which they are ground- 

 ed, have been discussed, as far as space and the writer's faculties permit- 

 ted, in the twentj^-four preceding chapters. But the result of the exami- 

 nation of evidence is not always belief, nor even suspension of judgment; 

 it is sometimes disbelief. The philosophy, therefore, of induction and ex- 

 perimental inquiry is incomplete, unless the grounds not only of belief, but 

 of disbelief, are treated of; and to this topic we shall devote one, and the 

 final, chapter. 



By disbelief is not here to be understood the mere absence of belief. 

 The ground for abstaining from belief is simply the absence or insufficiency 

 of proof ; and in considering what is sufficient evidence to support any 

 given conclusion, we have already, by implication, considered what evidence 

 is not sufficient for the same purpose. By disbelief is here meant, not the 

 state of mind in which we form no opinion concerning a subject, but that 

 in which we are fully persuaded that some opinion is not true; insomuch 

 that if evidence, even of great apparent strength (whether grounded on 

 the testimony of others or on our own supposed perceptions), were pro- 

 duced in favor of the opinion, we should believe that the witnesses spoke 

 falsely, or that they, or we ourselves if we were the direct percipients, were 

 mistaken. 



That there are such cases, no one is likely to dispute. Assertions for 

 which there is abundant positive evidence are often disbelieved, on account 

 of what is called their improbability, or impossibility. And the question 

 for consideration is what, in the present case, these words mean, and how 

 far and in what circumstances the properties which they express are suffi- 

 cient grounds for disbelief. 



§ 2, It is to be remarked, in the first place, that the positive evidence 

 produced in support of an assertion which is nevertheless rejected on the 

 score of impossibility or improbability, is never such as amounts to full 

 proof. It is always grounded on some approximate generalization. The 

 fact may have been asserted by a hundred witnesses ; but there are many 

 exceptions to the universality of the generalization that what a hundred 

 witnesses affirm is true. We may seem to ourselves to have actually seen 

 the fact ; but that we really see what we think we see, is by no means a 

 universal truth ; our organs may have been in a morbid state ; or we may 

 have inferred something, and imagined that we perceived it. The evi- 

 dence, then, in the affirmative being never more than an approximate gen- 

 eralization, all will depend on what the evidence in the negative is. If that 

 also rests on an approximate generalization, it is a case for comparison of 

 probabilities. If the approximate generalizations leading to the affirmative 

 are, when added together, less strong, or, in other words, farther from be- 

 ing universal, than the approximate generalizations which support the neg- 

 ative side of the question, the proposition is said to be improbable, and is 



