There is, however, one way in which this criterion is still too restrictive: it assumes that in order to have a concept we must first be acquainted with a word. Doubtless this is usually the case, but it is not always the case. A person may have something in mind for which no word yet exists, and he may then invent a word for it; or he may use an old word in a new sense, giving it a meaning it never had before. In either case, it seems plausible to say that he had the concept prior to the existence (or new usage) of the word. When the first physicists adapted the use of the common word "energy" for their own special purposes, they had in mind a highly abstract concept, and they presumably had this concept in mind before they had a word for it. Doubtless there are many concepts that one cannot have without much prior acquaintance with language, but this cannot be the case for all concepts, else how would language have got started? Using a word correctly seems to be a consequence of having the concept, but not a precondition of having it: that is, if you have a concept, and know the word for it, you will then be able to use the word but having the concept is not the same thing as being able to use the word