Is it cruel to kill cattle in slaughterhouses where live cattle can smell the blood of the dead? Or to spank children in order to teach them how to behave? The point is not that we couldn’t argue our way to one position or the other on these questions; it’s only to say that when we disagree, it won’t always be because one of us just doesn’t understand the value that’s at stake. It’s because applying value terms to new cases requires judgment and discretion. Indeed, it’s often part of our understanding of these terms that their applications are meant to be argued about. They are, to use another piece of philosopher’s jargon, essentially contestable. For many concepts, as W.B. Gallie wrote in introducing the term, “proper use inevitably involves endless disputes about their proper use on the part of users.” Evaluative language, I’ve been insisting, aims to shape not just our acts but our thoughts and our feelings. When we describe past acts with words like “courageous” and “cowardly,” “cruel” and “kind,” we are shaping what people think and feel about what was done—and shaping our understanding of our moral language as well. Because that language is open-textured and essentially contestable, even people who share a moral vocabulary have plenty to fight about.
From Cosmopolitanism by Kwame Anthony Appiah, page 59