Book excerpt: This book asserts that the better one understands the causes of behavior, the better one can apply that knowledge to produce a better world. It describes the mechanisms that cause human behavior, such as freedom of will, in a manner consistent with religious beliefs. It also asserts that all avenues for studying human behavior, like intuition and prayer, are acceptable and necessary. Thus, when studying the agent of human action, we must rely on faith, logic, and intuition, in addition to the full use of empirical science. Principles of Psychology for People of God begins with a description of the nervous system and continues with chapters on development, perception, internal states, learning, memory, and the ultimate selection of behaviors. Nevertheless, it steadfastly emphasizes that behavior is not produced by physical mechanisms alone, but also by a non-material spirit that can transcend some inheritances and environments.