Theology is doubly revealed and many Christians often ignore God’s natural revelation as being a valid object of interpretation. It’s all too often that many Christians reject many valid scientific theories.
“Theology is properly distinguished as natural and revealed. The former is concerned with the facts of nature so far as they reveal God and our relation to him, and the latter with the facts of Scripture.” –Charles Hodge
Theology refers to the all encompassing knowledge of God.
Theology of Nature refers to the Book of Nature as revealed in Scripture (Ps. 19.1-4; Rom. 1.20) Look at Psalm 19. When speaking of God it refers to his general name (El, Heb., continuous, abundant, universal). Some of the themes are creation’s contingency, Imago Dei, Stewardship, the fall, etc.
Natural Theology refers to the metaphysical implications of, say, intelligent design, the beginning of the universe, the moral law, beauty, etc.
“Some people, in order to discover God, read books. But there is a great book: the very appearance of created things. Look above you! Look below you! Note it. Read it. God, whom you want to discover, never wrote that book with ink. Instead he set before your eyes the things that he made. Can you ask for a louder voice than that?” -Augustine
“I want creation to penetrate you with so much admiration that wherever you go, the least plant may bring you a clear remembrance of the Creator… One blade of grass or one speck of dust is enough to occupy your entire mind in beholding the art with which it has been made.” –Basil the Great“Any error about creation also leads to an error about God.” –Thomas Aquinas
Why is this distinction so important? There are salvific consequences (Rom. 2.12-16). Understanding theology is understanding God. Just as the heavens declare the glory of God so should we in what we do and who we are. All of nature glorifies God (Ps. 19.1-4, 96.11-12). Sinners fall short of the glory of God (Rom. 3.23). Saints declare the glory of God (Ps. 34.3, 145.10; 1 Cor. 10.31).