Computational linguist Kees van Deemter: “A vague concept allows borderline cases … such as the word ‘grey’. Some birds are clearly grey, some are clearly not, while others are somewhere in between. The fact that such birds exist makes ‘grey’ a vague concept. The vagueness does not arise from insufficient information: some concepts are fundamentally vague. … [And] vagueness is crucial if you want to build computers and robots that communicate with people.”