Nothing certainly can be more improving to a Searcher into Nature, than Objections judiciously made to his Opinions, taken up perhaps too hastily: For such Objections oblige him to re-study the Point, consider every Circumstance carefully, compare Facts, make Experiments, weigh Arguments, and be slow in drawing Conclusions. And hence a sure Advantage results; for he either confirms a Truth, before too lightly supported; or discovers an Error, and receives Instruction from the Objector.
In this View I consider the Objections and Remarks you sent me, and thank you for them sincerely.
When he found that he was in error, it cost him no struggle to recant. For a while he believed the sea to be the grand source of lightning, and built up an imposing fabric of conclusions upon the belief; but he did not hesitate afterwards to admit that he had embraced this opinion too hastily. The same thing is true of the opinion that he held for a time, that the progress of a ship westward, across the Atlantic, is retarded by the diurnal motion of the earth. He supposed that the melting brought about by the action of lightning was a cold fusion until holes burnt in a floor by portions of a molten bell wire convinced him that this was not so.
I was too easily led into that error [he said] by accounts given even in philosophical books, and from remote ages downwards, of melting money in purses, swords in scabbards, etc. without burning the inflammable matters that were so near those melted metals. But men are, in general, such careless observers, that a philosopher can not be too much on his guard in crediting their relations of things extraordinary, and should never build an hypothesis on anything but clear facts and experiments, or it will be in danger of soon falling, as this does, like a house of cards.
In one of his letters to Collinson, he declared that, even though future discoveries should prove that certain conjectures of his were not wholly right, yet they ought in the meantime to be of some use by stirring up the curious to make more experiments and occasion more exact disquisitions. Following out the same thought in another letter to Collinson he concluded: "You are at liberty to communicate this paper to whom you please; it being of more importance that knowledge should increase, than that your friend should be thought an accurate philosopher." In a letter to John Lining, in which he described the experiment from which Cavendish deduced the law of which we have spoken, he observed:
I find a frank acknowledgement of one's ignorance is not only the easiest way to get rid of a dificulty, but the likeliest way to obtain information, and therefore I practise it: I think it an honest policy. Those who affect to be thought to know everything, and so undertake to explain everything often remain long ignorant of many things that others could and would instruct them in, if they appeared less conceited.
The fact is that Franklin had such a keen sense of the dignity and invincibility of truth that he could not be induced to enter into any personal controversy about it. His feelings with regard to such controversies are pointedly expressed in the Autobiography in connection with the attack made by the Abbé Nollet upon his electrical experiments.
I once purpos'd [he said] answering the abbé, and actually began the answer; but, on consideration that my writings contain'd a description of experiments which anyone might repeat and verify, and if not to be verifi'd, could not be defended; or of observations offer'd as conjectures, and not delivered dogmatically, therefore not laying me under any obligation to defend them; and reflecting that a dispute between two persons, writing in different languages, might be lengthened greatly by mistranslations, and thence misconceptions of one another's meaning, much of one of the abbé's letters being founded on an error in the translation, I concluded to let my papers shift for themselves, believing it was better to spend what time I could spare from public business in making new experiments, than in disputing about those already made.
But in this instance, too, after all, he acted upon the principle, stated in one of his letters to Cadwallader Colden, that he who removes a prejudice, or an error from our minds contributes to their beauty, as he would do to that of our faces who should clear them of a wart or a wen. He went through his experiments again, and satisfied himself that the Abbé had not shaken his positions. At one time, when he was hesitating as to whether he should reply to him, he heard that D'Alibard was preparing to do so. "Perhaps," he wrote to his friend, James Bowdoin, "it may then appear unnecessary for me to do anything farther in it. And will not one's vanity be more gratified in seeing one's adversary confuted by a disciple, than even by one's self?" When Wilson published a pamphlet, contending that lightning rods should be blunt rather than pointed, he simply observed, "I have not answered it, being averse to Disputes."
Not only his temperament but his general mental attitude was instinctively scientific. As we have seen, while Whitefield's other auditors were standing mute and spellbound, he was carefully computing the distance that the words of the orator would carry. As we have also seen, when his soldiers were cutting down the giant pines at Gnadenhutten, he had his watch out, deep in his observation of the time that it took them to fell a tree. When his friend, Small, complained of deafness, he wrote to him that he had found by an experiment at midnight that, by putting his thumb and fingers behind his ear, and pressing it out and enlarging it as it were with the hollow of his hand, he could hear the tick of a watch at the distance of forty-five feet which was barely audible at a distance of twenty feet without these aids. Even in his relations to the simplest concerns of life, he had always the eye of a man of science to weight, measure, dimension and distance. If anyone wishes to see how easily he reduced everything to its scientific principles, let him read Franklin's letter to Oliver Neave, who thought that it was too late in life for him to learn to swim. With the confidence bred by a proper sense of the specific gravity of the human body as compared with that of water, Franklin said, there was no reason why a human being should not swim at the first trial. If Neave would only wade out into a body of water, until it came up to his breast and by a cast of his hand sink an egg to the bottom, between him and the shore, where it would be visible, but could not be reached except by diving, and then endeavor to recover it, he would be surprised to find what a buoyant thing water was.