Toward contextualization, essential general distinctions are discussed regarding the interpretation of psychology throughout Western history, especially the distinction between natural and human science. Providing arguments against attempts to deny the selection of, and commitment to, principles, for example, the positions of eclecticism and anarchism, the chapter discusses principles and distinctions associated with hermeneutics and the "philosophy of psychology," so that readers may employ such distinctions to think through the systems of psychology in later chapters. The general distinctions used to organize the material of the remaining chapters is introduced; that is, in the remaining chapters, the philosophical principles of psychology constituting the various historical systems in the West are organized in terms of: structure, function, and methodology.