Faraday’s mind was of a very individual turn; he could not walk along the beaten tracks, but must pursue truth wherever it led him. His dogged tenacity for exact fact was accompanied by a perfect fearlessness of speculation. He would throw overboard without hesitation the most deeply-rooted notions if experimental evidence pointed to newer ideas. He had learned to doubt the idea of _poles_; so he outgrew the idea of _atoms_, which he considered an arbitrary conception. Many who heard his bold speculations and his free coinage of new terms deemed him vague and loose in thought. Nothing could be more untrue. He let his mind play freely about the facts; he framed thousands of hypotheses, only to let them go by if they were not supported by facts. “He is the wisest philosopher,” he said in a lecture on the nature of matter, “who holds his theory with some doubt--who is able to proportion his judgment and confidence to the value of the evidence set before him, taking a fact for a fact and a supposition for a supposition, as much as possible keeping his mind free from all source of prejudice; or, where he cannot do this (as in the case of a theory), remembering that such a source is there.” In one of his later experimental researches he wrote:-- As an experimentalist, I feel bound to let experiment guide me into any train of thought which it may justify; being satisfied that experiment, like analysis, must lead to strict truth if rightly interpreted; and believing also that it is in its nature far more suggestive of new trains of thought and new conditions of natural power. [Sidenote: WHY NO SUCCESSOR.]