“We are dealing with relativism if a person says one of these four things:

–          There is no objective, external standard for measuring the truth or falsehood of a statement.

–          There may be an external standard, but we can’t know if there is.

–          There is an objective standard; we know it is there, but no one can figure out what it means, so it can’t function as a universally valid standard.

–          There may be an external, objective standard, but I don’t care what it is.  I’m not going to submit to it.  I’m not going to base my convictions on it.  I will create my own standards.

Consider the statement “Sexual relations between two males is wrong.”  Two people may disagree on this and not be relativists.  They may both say, “There is an objective, external standard for assessing this statement, namely, God’s will revealed in the inspired Christian Bible.”  One may say the Bible teaches that this is wrong, and the other may say that the Bible permits it.  This would not be relativism.

Relativism comes into play when someone says, “There is no knowable, objective, external standard for right and wrong that is valid for everyone.  And so your statement that sexual relations between two males is wrong is relative to your standard of assessment.”  This is the essence of relativism: no one standard of true and false, right and wrong, good and bad, or beautiful and ugly, can preempt any other standard.  No standard is valid for everyone.

What does this imply about truth?

Relativists may infer from this that there is no such thing as truth.  It is simply an unhelpful and confusing category since there are no external, objective standards that are valid for everyone.  Or they may continue to use the word “truth” but simply mean by it “what conforms to your subjective preferences.”  You may prefer the Bible or the Koran or the Book of Mormon or Mao’s Little Red Book or the sayings of Confucius or the philosophy of Ayn Rand or your own immediate desires or any of a hundred other standards.   In that case you will hear the language of “true for you but not true for me.”  In either case, we are dealing with relativism.

In sum, then, the essence of relativism is the conviction that truth-claims – like “sexual relations between two males is wrong” – are not based on standards of assessment that are valid for everyone.  There are no such standards that we can know.  Concepts like true and false, right and wrong, good and bad, beautiful and ugly, are useful for expressing personal preferences or agreed upon community values, but they have no claim to be based on a universally valid standard.”

Copied from pages 97-99 of John Piper’s book “Think: The Life of the Mind and the Love of God.”