14 No faith in God can for long survive pure and unalloyed without the support of faith in Christ. "No one knoweth who the Son is, but the Father: and who the Father is, but the Son and to whom the Son will reveal Him" ( Luke x. 22). "Now this is eternal life: That they may know thee, the only true God, and Jesus Christ whom thou has sent" ( John xvii. 3). Nobody, therefore, can say: "I believe in God, and that is enough religion for me," for the Savior's words brook no evasion: "Whosoever denieth the Son, the same hath not the Father. He that confesseth the Son hath the Father also" (1 John ii. 23).
Source: Mit Brennender Sorge (Vatican.va)