Because, although they knew God, they did not glorify Him or give thanks to Him as God, but became futile in their imaginations, and their foolish hearts were darkened.
Is there a God or is there not? That question eclipses all other questions that men might ask. Should you feel that this statement is merely the opinion of a theologian or minister, let me give it to you from another source. Dr. Mortimer Adler, former professor at the University of Chicago and the associate editor of that massive set of volumes entitled, The Great Books of the Western World—60 volumes of the greatest writings of the greatest minds of the Western world—says that with the exception of certain mathematicians and physicists, all the authors included in the Great Books are represented in the chapter on God.
In the Syntopicon of The Great Books, the two-volumes that deal with all of the subjects covered by all of the various authors, Dr. Adler says that the subject of God is the one that is handled by more authors than any other. “The reason is obvious,” said Dr. Adler. “More consequences for thought and action follow the affirmation or denial of God than the answering of any other basic question.”
Question to ponder: What consequences flow from belief or unbelief in God?