All are sure in their days except the most wise ... He is the wisest philosopher who holds his theory with some doubt.

I cannot conceive curved lines of force without the conditions of a physical existence in that intermediate space.

I think chemistry is being frittered away by the hairsplitting of the organic chemists; we have new compounds discovered, which scarcely differ from the known ones and when discovered are valueless-very illustrations perhaps of their refinements in analysis, but very little aiding the progress of true science.

Nothing is to wonderful to be true.

The philosopher should be a man willing to listen to every suggestion,but determined to judge for himself.He should not be a respector of persons,but of things.Truth should be his primary object.

Occasionally and frequently the exercise of the judgment ought to end in absolute reservation. It may be very distasteful, and great fatigue, to suspend a conclusion; but as we are not infallible, so we ought to be cautious; we shall eventually find our advantage, for the man who rests in his position is not so far from right as he who, proceeding in a wrong direction, is ever increasing his distance.

Speculations? I have none. I am resting on certainties.