In its most common sense, philosophical methodology is the field of inquiry studying the methods used to do philosophy. But the term can also refer to the methods themselves. It may be understood in a wide sense as the general study of principles used for theory selection, or in a more narrow sense as the study of ways of conducting one's research and theorizing with the goal of acquiring philosophical knowledge. Philosophical methodology investigates both descriptive issues, such as which methods actually have been used by philosophers, and normative issues, such as which methods should be used or how to do good philosophy.