Martin G. Colins said

“Many profess faith in God but do not even know Him! Their worship is vain, not knowing whom they worship and learning the doctrines of man, not God. A belief imparted by parents or other authority figures that God exists is not sufficient to establish contact with Him. For example, the Pharisees, familiar with the God of the Old Testament and believing they were in good standing with Him, received Christ’s rebuke that their faith was in vain. This is true of most people today who think they “know the Lord” and profess faith toward Him.