For most of us, the term “theory” is a little intimidating and suggests something that is boring or of little value to us. What you might not realize is that you depend upon theories to help you make it through each day. Theories are not just abstract, vague, complex sets of weird ideas. Instead, they can be simple and practical principles, guidelines, hunches, and predictions that help you make sense and respond effectively to the world. You develop, test, and tweak a set of personal theories that help you interpret perceptions and guide your behaviors. Your creation of personal theories reflects an important principle that is also true of the theories included in this text: humans are theory creating beings.