Absolute Truth - Inflexible Reality
"Absolute truth" is defined as inflexible reality: fixed, invariable, unalterable facts. For example, it is a fixed, invariable, unalterable fact that there are absolutely no square circles and there are absolutely no round squares.
Absolute Truth vs. Relativism
While absolute truth is a logical necessity, there are some religious orientations (atheistic humanists, for example) who argue against the existence of absolute truth. Humanism's exclusion of God necessitates moral relativism. Humanist John Dewey (1859-1952), co-author and signer of the Humanist Manifesto 1 (1933), declared, "There is no God and there is no soul. Hence, there are no needs for the props of traditional religion. With dogma and creed excluded, then immutable truth is also dead and buried. There is no room for fixed, natural law or moral absolutes." Humanists believe one should do, as one feels is right.
Absolute Truth - A Logical Necessity
You can't logically argue against the existence of absolute truth. To argue against something is to establish that a truth exists. You cannot argue against absolute truth unless an absolute truth is the basis of your argument. Consider a few of the classic arguments and declarations made by those who seek to argue against the existence of absolute truth
"There are no absolutes." First of all, the relativist is declaring there are absolutely no absolutes. That is an absolute statement. The statement is logically contradictory. If the statement is true, there is, in fact, an absolute - there are absolutely no absolutes.
"Truth is relative." Again, this is an absolute statement implying truth is absolutely relative. Besides positing an absolute, suppose the statement was true and "truth is relative." Everything including that statement would be relative. If a statement is relative, it is not always true. If "truth is relative" is not always true, sometimes truth is not relative. This means there are absolutes, which means the above statement is false. When you follow the logic, relativist arguments will always contradict themselves.
"Who knows what the truth is, right?" In the same sentence the speaker declares that no one knows what the truth is, then he turns around and asks those who are listening to affirm the truth of his statement.
"No one knows what the truth is." The speaker obviously believes his statement is true.
There are philosophers who actually spend countless hours toiling over thick volumes written on the "meaninglessness" of everything. We can assume they think the text is meaningful! Then there are those philosophy teachers who teach their students, "No one's opinion is superior to anyone else's. There is no hierarchy of truth or values. Anyone's viewpoint is just as valid as anyone else's viewpoint. We all have our own truth." Then they turn around and grade the papers!