They claim to know God, but by their actions they deny him. They are detestable, disobedient and unfit for doing anything good.
Many people claim the title "Christian" - how can we tell if they really do? Obviously only God can see into our hearts, minds and souls, but we can tell by people`s lifestyles what they value and if their priorities and morals are rooted in Truth. What does the way you live your life tell other people about you?
LeRoy Eims on the importance of Scripture memory: "I think two of the master strokes of the devil have been to convince people he doesn't exist, and that Scripture memory is only for children. He remembers the humility of defeat when Jesus Christ, who was tempted in all points like as we are, met him with the Word of God." (What Every Christian Should Know About Growing; p. 26-27)