Negation, or denial, is the opposite of affirmation. It may be something that somebody does ("I deny what you have said") or the answer "No" to a question, but its full expression is generally a sentence. One sentence or statement may be the negation or denial of another, or we may call a statement simply a negation, or a negative statement, as opposed to an affirmative one, or affirmation. A negation in the last sense will contain some sign of negation, such as the "not" in "Grass is not pink" or "Not all leaves are green," the "no" in "No Christians are communists," or the phrase "it is not the case that" in "It is not the case that grass is pink." The negation of a sentence may simply be the same sentence with "it is not the case that" prefixed to it, or it may be some...