In the yesterday's class, I first explained the importance of metaphor, because the students were not good at 3rd homework exercise, that is, "select a character, and list and categorize the metaphors in his or her remarks". Many students didn't understand the difference among analogy, metonymy and synecdoche. So I first explained what metaphor was. A metaphor expresses an idea or a thing in other idea or thing, and the metaphorical target idea is more abstract than the original. For example, "a discussion is a war" is a metaphor based on analogy, and "discussion" is more abstract idea than "war". However, there is a different discussion from "war", for example, we can discuss in a manner of "give and take". So a metaphor lights up only one aspect of the target idea, and the other aspects are hidden in the shadow. So much so that, we can understand the cultural and personality background of a person by analyzing what kinds of metaphors the person uses.
By the way, are there any other expressions except for metaphor? The answer is no. After all, language itself is a metaphor, because the relation between signifian and signifie is arbitral, as Ferdinand de Saussure pointed out. That is, a word(signifian) is not its object(signifie) itself. Although language is only a sign, we have no other choice but to express an object using language. This is the just thing that an idea is expressed by the other idea. Well then, how is the relation between signifian and signifie determined? That is determined by difference and deferral, these two characters are mixed into "differral" by Jack Delida. "Difference" means that a signifie is distinguished from the other things, for example, "red" as a signifian distinguish "red" as a signifie from the other colors. But the meaning of word cannot be determined only by "difference", because we cannot understand what kind of "red" only by "red". So to determine what kind of red the "red" means, we need another words, such as shallow, shiny, like a baby cheeks and so on. So a meaning of word can be determined after appearance of the word, that is "deferral". So much so that, we can also understand the personality of a person if we see what kinds of words the person uses.