Psychology is the biological science that studies the individual's reactions to his external and internal environment. These reactions can be: conscious, subconscious and unconscious. The conscious reactions are: conscience, will and intelligence. The subconscious reactions are: emotions, feelings, dreams and habits. The unconscious reactions are all instincts. The individual can have both immediate and mediate reactions. The methods of study of Psychology are direct and indirect observation, and directed introspection. The objectives of Psychology are the personal adjustment and the adaptation of the individual to the environment. This view of Psychology is a Reactionism.