Evil, by definition, is that which endangers the good, and the good is that which we perceive as a value.

All living beings have received their weapons through the same process of evolution that moulded their impulses and inhibitions; for the structural plan of the body and the system of behaviour of a species are parts of the same whole.... Wordsworth is right: there is only one being in possession of weapons which do not grow on his body and of whose working plan, therefore, the instincts of his species know nothing and in the usage of which he has no correspondingly adequate inhibition.

I believe that present day civilized man suffers from insufficient discharge of his aggressive drive

The fidelity of a dog is a precious gift demanding no less binding moral responsibilities than the friendship of a human being.

Most people have forgotten how to live with living creatures, with living systems and that, in turn, is the reason why man, whenever he comes into contact with nature, threatens to kill the natural system in which and from which he live.

Barking dogs may occasionally bite, but laughing men hardly ever shoot!

It is a good morning exercise for a research scientist to discard a pet hypothesis every day before breakfast. It keeps him young.