I must interpret the life about me as I interpret the life that is my own. My life is full of meaning to me. The life around me must be full of significance to itself. If I am to expect others to respect my life, then I must respect the other life I see, however strange it may be to mine. And not only other human life, but all kinds of life: life above mine, if there be such life; life below mine, as I know it to exist. Ethics in our Western world has hitherto been largely limited to the relations of man to man. But that is a limited ethics. We need a boundless ethics which will include the animals also.

Kulturphilosophie (1923) - Vol. 2 : Civilization and Ethics