One main factor in the upward trend of animal life has been the power of wandering.

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.

The study of mathematics is apt to commence in disappointment... We are told that by its aid the stars are weighed and the billions of molecules in a drop of water are counted. Yet, like the ghost of Hamlet's father, this great science eludes the efforts of our mental weapons to grasp it.

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

Without adventure all civilization is full of decay. Adventure rarely reaches its predetermined end. Columbus never reached China.

Dogmatism is the anti-Christ of learning.

There is only one subject matter for education, and that is Life in all its manifestations