Imagination is not to be divorced from the facts. It is a way of illuminating the facts.

The true method of discovery is like the flight of an aeroplane. It starts from the ground of particular observation; it makes a flight in the thin air of imaginative generalization; and it again lands for renewed observation rendered acute by rational interpretation.

Every intellectual revolution which has ever stirred humanity into greatness has been a passionate protest against inert ideas. Then, alas, with pathetic ignorance of human psychology, it has proceeded by some educational scheme to bind humanity afresh with inert ideas of its own fashioning.

From the moment of birth we are immersed in action, and can only fitfully guide it by taking thought.

Dogmatism is the anti-Christ of learning.

There are no whole truths: all truths are half-truths. It is trying to treat them as whole truths that plays to the devil.

Without deductive logic science would be entirely useless. It is merely a barren game to ascend from the particular to the general, unless afterwards we can reverse the process and descend from the general to the particular, ascending and descending like angels on Jacob's ladder.