All scientific knowledge to which man owes his role as master of the world arose from playful activities.

Hatred of humanity and love of animals make a very bad combination.

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

More than any other product of human scientific culture scientific knowledge is the collective property of all mankind.

It ought to be realized by all dog owners that obesity shortens a dog's life quite considerably, a life which is much too short anyhow.

Just thinking that my dog loves me more than I love him, I feel shame.

...he who has seen the intimate beauty of nature cannot tear himself away from it again. He must become either a poet or a naturalist and, if his eyes are keen and his powers of observation sharp enough, he may well become both.