If the twentieth century is to be better than the nineteenth, it will be because there are among us men who walk in Priestley's footsteps....To all eternity, the sum of truth and right will have been increased by their means; to all eternity, falsehoods and injustice will be the weaker because they have lived.

Extinguished theologians lie about the cradle of every science, as strangled snakes beside that of Hercules

The known is finite, the unknown infinite; intellectually we stand on an islet in the midst of an illimitable ocean of inexplicability. Our business in every generation is to reclaim a little more land, to add something to the extent and the solidity of our possessions.

The ultimate court of appeal is observation and experiment... not authority.

In matters of intellect, follow your reason as far as it will take you, without regard for any other consideration.

The clergy are at present divided into three sections: an immense body who are ignorant; a small proportion who know and are silent; and a minute minority who know and speak according to their knowledge.

There is far too much of the feeding-bottle in education and young people ought to be supplied with good intellectual food and then left to help themselves.