“Humans are animals of habit.”
“What we believe as human nature in actuality is human habit.”
“The difference between animals and humans is that animals change themselves for the environment, but humans change the environment for themselves.”
“Humans are animals, but aren’t we supposed to be civilized animals?”
“With most animals, as with man, the alertness of the senses diminishes after years of work, after domestic habits and progress of culture.”
“Let animals live like animals; let humans live like humans. That's my whole philosophy in a sentence.”