This is the text of a lecture delivered in 1910 by Roosevelt to students and others at Oxford University. It was part of a series called The Romanes Lectures, delivered by invitation. The fundamental principle that underpins Roosevelt's lecture is that science, history, and literature are inseparable one from another. Our biological evolution is in many ways no different from other life forms, except in that we have learned to judge ourselves and reflect on and even modify our growth.