Consider as an example the question “What is time?” as Saint Augustine and others have asked it. At first sight what this question asks for is a definition, but then immediately the question arises: “What should we gain by a definition, as it can only lead us to other undefined terms?” And why should one be puzzled just by the lack of a definition of time, and not by the lack of a definition of “chair”? Why shouldn't we be puzzled in all cases where we haven't got a definition? Now a definition often clears up the grammar of a word. And in fact it is the grammar of the word “time” which puzzles us. We are only expressing this puzzlement by asking a slightly misleading question, the question: “What is … ?” This question is an utterance of unclarity, of mental discomfort; and it is comparable with the question “Why?” as children so often ask it. This too is an expression of a mental discomfort, and doesn't necessarily ask for either a cause or a reason. (Hertz, Principles of Mechanics). Now the puzzlement about the grammar of the word
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“time” arises from what one might call apparent contradictions in that grammar.