"We must never assume that which is incapable of proof."

“No deeply-rooted tendency was ever extirpated by adverse argument. Not having originally been founded on argument, it cannot be destroyed by logic.”

“I would not have the reader conclude that because I advocate plain-speaking even of unpopular views, I mean to imply that originality and sincerity are always in opposition to public opinion. There are many points both of doctrine and feeling in which the world is not likely to be wrong. But in all cases it is desirable that men should not pretend to believe opinions which they really reject, or express emotions they do not feel. And this rule is universal. Even truthful and modest men will sometimes violate the rule under the mistaken idea of being eloquent by means of the diction of eloquence. This is a source of bad Literature.”

“The first obligation of Simplicity is that of using the simplest means to secure the fullest effect. But although the mind instinctlvely rejects all needless complexity, we shall greatly err if we fail to recognise the fact, that what the mind recoils from is not the complexity, but the needlessness.”

“Obedient to the primary impulse of adequate expression, the style of a complex subject should be complex; of a technical subject, technical; of an abstract subject, abstract; of a familiar subject, familiar; of a pictorial subject, picturesque.”

“The art of a great writer is seen in the perfect fitness of his expressions. He knows how to blend vividness with vagueness, knows where images are needed, and where by their vivacity they would be obstacles to the rapid appreciation of his thought.”

“Every one who has seriously investigated a novel question, who has really interrogated Nature with a view to a distinct answer, will bear me out in saying that it requires intense and sustained effort of imagination. The relations of sequence among the phenomena must be seen; they are hidden; they can only be seen mentally; a thousand suggestions rise before the mind, but they are recognised as old suggestions, or as inadequate to reveal what is sought; the experiments by which the problem may be solved have to be imagined; and to imagine a good experiment is as difficult as to invent a good fable, for we must have distinctly present — clear mental vision — the known qualities and relations of all the objects, and must see what will be the effect of introducing some new qualifying agent. If any one thinks this is easy, let him try it: the trial will teach him a lesson respecting the methods of intellectual activity not without its use.”