This book demonstrates the relevance of biological knowledge to many questions that concern philosophers and psychologists,such as perception, freedom, determinism and ethical values. Conversely, it indicates to biologists the importance of understanding philosophical concepts. The author describes in simple terms what research and experiment has revealed about the brain and its functions. He shows that perception is not a passive process but an active search for information. He suggests that human knowledge may be a special development of the process of gathering information for life which is essential for all organisms.