When quite a young man he drew the following ideal portrait:--"The philosopher should be a man willing to listen to every suggestion, but determined to judge for himself. He should not be biassed by appearances, have no favourite hypothesis, be of no school, and in doctrine have no master. He should not be a respecter of persons, but of things. Truth should be his primary object. If to these qualities be added industry, he may indeed hope to walk within the veil of the temple of Nature." This ideal he must steadily have kept before him, and not unfrequently in after days he gave utterance to similar thoughts. Here are two instances, the first from a lecture thirty years afterwards, the second from a private letter:--"We may be _sure_ of facts, but our interpretation of facts we should doubt. He is the wisest philosopher 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." The letter is to Mr. Frederick Field, and relates to a paper on the existence of silver in the water of the ocean.
"ROYAL INSTITUTION, _21st October, 1856_.
"Your paper looks so well, that though I am of course unable to become security for the facts, I have still thought it my duty to send it to the Royal Society. Whether it will appear there or not I cannot say,--no one can say even for his own papers; but for my part, I think that as facts are the foundation of science, however they may be interpreted, so they are most valuable, and often more so than the interpretations founded upon them. I hope your further researches will confirm those you have obtained: but I would not be too hasty with them,--rather wait a while, and make them quite secure.
How pleasant it would have been to peep into his mind and watch the process by which he was transformed into the very image of his ideal philosopher! He has partially told us the secret in two remarkable lectures, one of which was delivered before the City Philosophical Society when he was only twenty-seven years of age, while the other formed part of a series on Education at Albemarle Street. Copious extracts from the first are given by Dr. Bence Jones; the second was published at the time. In the early lecture, which is "On the Forms of Matter," he points out the advantages and dangers of systematizing, and winds up his remarks with--