Big words, but so important. Euphemism: the substitution of a mild, indirect or vague for one thought to be offensive, harsh or blunt. As in “the final solution” or “pro-choice.” Metaphor: a figure of speech in which a term or phrase is applied to something to which it is not literally applicable in order to suggest a resemblance. As in “our God is a mighty fortress.” Epistemology: a branch of philosophy that investigates the origin, nature, methods and limits of human knowledge. As in how you know what you know. Presupposition: a condition taken for granted, usually unconsciously, in order for a statement to be true in the language in which the statement was made. “The boy jumped over the stool.” In this simple example, presuppositions are: the boy is capable of jumping (he is not bedridden, has either both legs or effective prostheses, the stool is low enough that this boy can jump it and the stool was in front of rather than behind the boy). Even more obvious, the stool and a boy are observable, and observer has the ability to see the act.
It may seem as though presuppositions are so obvious that they don’t need to be stated. However, the opposite is also true, presuppositions are so unconscious that they need to be made explicit. Most opinions are formed from presuppositions that the opinion stater is not conscious of, and many of those presuppositions are wrong. That makes challenging opinions, at least as a form of debate, futile. People will vociferously defend their opinions even when they are based on wrong information because they are really defending their presuppositions about the world, their worldview.
To have a meaningful or persuasive debate, we must understand the underlying presuppositions, and question the epistemology–how do you know what you believe, what makes you think it true? It isn’t easy scoping out a person’s presuppositions. They will usually show up in the metaphors and euphemisms that they unconsciously use. For instance, if someone says they are “pro-choice”, that euphemism contains the following presuppositions (whether you like it or not, since all of these presuppositions are necessary to countenance the euphemism): the life of the mother, i.e. a fully alive person, and even her lifestyle is more important than the baby’s life; the mother has the right to decide whether her baby lives or dies; having the power to choose to end life for whatever reason, even to improve your lifestyle temporarily, is more important than the other life itself; the baby isn’t a human being until she or he passes out of the mother.
Just imagine if a pro-choice person could or would engage in a debate and was put in the position of defending those presuppositions. How many of them would defend all those presuppositions? If you disagree with even one of them, then you either would have to oppose aborting babies, or argue that your right to end life trumps all other considerations. Then it becomes simply a matter of power.