This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book is concerned with intrapsychic explanations, explanations that use concepts based on psychological processes and “structures” within the mind. These explanations may focus on the contents of the mind, such as the existence of particular desires, emotions or thoughts, but typically define and utilize more complicated processes and structures such as ‘‘defense mechanisms,” “complexes,” and “system principles.” Social learning theory takes into account the fact that humans are more complex than lower animals, and introduces a limited number of intrapsychic processes in order to provide a more complete explanation of human behavior. The book focuses on the fact that psychological processes have been divided into one of the three types, depending on whether they focus on desires, thoughts, or emotions (commonly called conation, cognition, and affect, respectively).