The study of knowledge has for over 2000 years been a province of philosophy. Research is uncovering unexpected links between our capacity for knowledge and the struggle for survival and reproductive success. If we really want to understand the nature of learning, rationality and intelligent thought, it is now less to philosophers than to evolutionary biologists that we should turn. In this book, Plotkin offers a three-dimensional theory of our nature. He explores the idea of Universal Darwinism: the same basic mechanisms may underlie not only the origin of species but the functioning of the immune system, the development of language and even the progress of science. Natural selection itself can usefully be understood as a process of the acquisition of biological knowledge essential to survival. After instinct and knowledge acquired by trial and error comes the jointly shared knowledge we call culture, the final level on which we all operate.