Here is an induction corresponding with Bacon's analysis and ending in a monstrous absurdity. In what then does this induction differ from the induction which leads us to the conclusion that the presence of the sun is the cause of our having more light by day than by night? The difference evidently is not in the kind of instances, but in the number of instances; that is to say, the difference is not in that part of the process for which Bacon has given precise rules, but in a circumstance for which no precise rule can possibly be given. If the learned author of the theory about Jacobinism had enlarged either of his tables a little, his system would have been destroyed. The names of Tom Paine and William Wyndham Grenville would have been sufficient to do the work.
It appears to us, then, that the difference between a sound and unsound induction does not lie in this, that the author of the sound induction goes through the process analysed in the second book of the Novum Organum, and the author of the unsound induction through a different process. They both perform the same process. But one performs it foolishly or carelessly; the other performs it with patience, attention, sagacity, and judgment. Now precepts can do little towards making men patient and attentive, and still less towards making them sagacious and judicious. It is very well to tell men to be on their guard against prejudices, not to believe facts on slight evidence, not to be content with a scanty collection of facts, to put out of their minds the idola which Bacon has so finely described. But these rules are too general to be of much practical use. The question is, What is a prejudice? How long does the incredulity with which I hear a new theory propounded continue to be a wise and salutary incredulity?
When does it become an idolum specus, the unreasonable pertinacity of a too sceptical mind? What is slight evidence?
What collection of facts is scanty? Will ten instances do, or fifty, or a hundred? In how many months would the first human beings who settled on the shores of the ocean have been justified in believing that the moon had an influence on the tides? After how many experiments would Jenner have been justified in believing that he had discovered a safeguard against the small-pox? These are questions to which it would be most desirable to have a precise answer; but, unhappily, they are questions to which no precise answer can be returned.
We think, then, that it is possible to lay down accurate rules, as Bacon has done, for the performing of that part of the inductive process which all men perform alike; but that these rules, though accurate, are not wanted, because in truth they only tell us to do what we are all doing. We think that it is impossible to lay down any precise rule for the performing of that part of the inductive process which a great experimental philosopher performs in one way, and a superstitious old woman in another.
On this subject, we think, Bacon was in an error. He certainly attributed to his rules a value which did not belong to them. He went so far as to say, that, if his method of making discoveries were adopted, little would depend on the degree of force or acuteness of any intellect; that all minds would be reduced to one level, that his philosophy resembled a compass or a rule which equalises all hands, and enables the most unpractised person to draw a more correct circle or line than the best draftsmen can produce without such aid. [Novum 0rganum, Praef. and Lib. I Aph. 122.] This really seems to us as extravagant as it would have been in Lindley Murray to announce that everybody who should learn his Grammar would write as good English as Dryden, or in that very able writer, the Archbishop of Dublin, to promise that all the readers of his Logic would reason like Chillingworth, and that all the readers of his Rhetoric would speak like Burke. That Bacon was altogether mistaken as to this point will now hardly be disputed. His philosophy has flourished during two hundred years, and has produced none of this levelling. The interval between a man of talents and a dunce is as wide as ever; and is never more clearly discernible than when they engage in researches which require the constant use of induction.
It will be seen that we do not consider Bacon's ingenious analysis of the inductive method as a very useful performance.
Bacon was not, as we have already said, the inventor of the inductive method. He was not even the person who first analysed the inductive method correctly, though he undoubtedly analysed it more minutely than any who preceded him. He was not the person who first showed that by the inductive method alone new truth could be discovered. But he was the person who first turned the minds of speculative men, long occupied in verbal disputes, to the discovery of new and useful truth; and, by doing so, he at once gave to the inductive method an importance and dignity which had never before belonged to it. He was not the maker of that road; he was not the discoverer of that road; he was not the person who first surveyed and mapped that road. But he was the person who first called the public attention to an inexhaustible mine of wealth, which had been utterly neglected, and which was accessible by that road alone. By doing so he caused that road, which had previously been trodden only by peasants and higglers, to be frequented by a higher class of travellers.