At the moment our human world is based on the suffering and destruction of millions of non-humans. To perceive this and to do something to change it in personal and public ways is to undergo a change of perception akin to a religious conversion. Nothing can ever be seen in quite the same way again because once you have admitted the terror and pain of other species you will, unless you resist conversion, be always aware of the endless permutations of suffering that support our society.

The more outré and grotesque an incident is the more carefully it deserves to be examined.

There is a soul-jealousy that can be as frantic as any body-jealousy.

Well, I'm a bacteriologist, you know. I live in a nine-hundred-diameter microscope. I can hardly claim to take serious notice of anything that I can see with my naked eye.

The world is full of obvious things which nobody by any chance ever observes.

He had never seen a woman doctor before, and his whole conservative soul rose up in revolt at the idea. He could not recall any biblical injunction that the man should remain ever the doctor and the woman the nurse, and yet he felt as if a blasphemy had been committed.

One forms provisional theories and waits for time or fuller knowledge to explode them. A bad habit, Mr. Ferguson, but human nature is weak. Sherlock Holmes speaking with Dr. Watson.