Classicly

The author frankly confesses to his own belief in the psychic unity of all animate nature. Believing in a common source of life, a common law of living, and a common destiny for all creatures, he feels that to dignify the apes is not to degrade man but rather to exalt him.

Believing that a more perfect knowledge of these animals will bring man into closer fellowship and deeper sympathy with nature, and with an abiding trust that it will widen the bounds of humanity and cause man to realize that he and they are but common links in the one great chain of life, the author gives this work to the world. When once man is impressed with the consciousness that in some degree, however small, all creatures think and feel, it will lessen his vanity and ennoble his heart.