If you remember nothing else, remember this: Inspiration from outside one's self is like the heat in an oven. It makes passable Bath buns. But inspiration from within is like a volcano: It changes the face of the world.
We are like travellers using the cinders of a volcano to roast their eggs. Whilst we see that it always stands ready to clothe what we would say, we cannot avoid the question whether the characters are not significant of themselves.
The lessons of science should be experimental also. The sight of a planet through a telescope is worth all the course on astronomy; the shock of the electric spark in the elbow outvalues all theories; the taste of the nitrous oxide, the firing of an artificial volcano, are better than volumes of chemistry.