Dr. B. B. Warfield wrote in his masterful little book "The Plan of Salvation"
The deepest cleft which separates men calling themselves Christians in their conceptions of the plan of salvation, is that which divides what we may call the Naturalistic and the Supernaturalistic views. The line of division here is whether, in the matter of the salvation of man, God has planned simply to leave men, with more or less completeness, to save themselves, or whether he has planned himself to intervene to save them. The issue between the naturalist and the supernaturalist is thus the eminently simple but quite absolute one: Does man save himself or does God save him?