 A fifth meaning of rationality, due to Peirce (1955) and taken up by the American pragmatists, applies to the process of changing a belief rather than the Humean appraisal of a currently held belief. On Peirce’s view, people are plagued by doubt not by belief; we don’t expend effort testing the sturdiness of our beliefs, but rather focus on those that come into doubt. Since inquiry is pursued to remove the doubts we have, not certify the stable beliefs we already possess, principles of rationality ought to apply to the methods for removing doubt (Dewey 1960). On this view, questions of what is or is not substantively rational will be answered by the inquirer: for an agronomist interested in grass cover sufficient to crowd out an invasive weed, obtaining the grass-blade count of a lawn might be a substantively rational aim to pursue.