False facts are highly injurious to the progress of science, for they often endure long; but false views, if supported by some evidence, do little harm, for every one takes a salutary pleasure in proving their falseness.

In conclusion, it appears that nothing can be more improving to a young naturalist, than a journey in distant countries.

I have steadily endeavoured to keep my mind free so as to give up any hypothesis, however much beloved (and I cannot resist forming one on every subject), as soon as facts are shown to be opposed to it.

A fair result can be obtained only by fully stating and balancing the facts and arguments on both sides of each question.

As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.

If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find no such case.