Missionary letters of Saint Nikolaos Velimirovich (Volume II).
"You say you believe in God and you consider that enough. "Even the demons believe and are angry" (James 2:19). You as a human must have something more. Let's say someone owes you five different things, and he only pays you back one, will you not be angry? And from you the Creator asks five things, while you offer Him only one. These five things are: Faith in God, knowledge of God's love, knowledge of God's will , the knowledge of God's energy, the knowledge of God's judgment.
You could arrive at belief in God as any pagan would, by observing nature, and concluding that matter presupposes a Creator. But the pagan cannot know everything else without the Gospel of Christ...
Therefore, faith in God alone is not enough, but all the things that the Savior of the world announced to people and asked of them are also necessary. For if only that which our nature hints at, and which you consider sufficient, were sufficient, then the coming of the Son of God into the world would have been useless, and His passions on the cross foolish. Therefore make haste, until death comes, to clothe the dead skeleton of your faith with flesh and life."