Some have imbibed the attitude of being seemingly allergic to any notion of natural theology (or common grace). Hesitant to afford the denomination of "revelation" to anything apart from Scripture, these people eschew the biblically-sound fact that all truth that can be properly called truth is either of the character of natural or special revelation, the former disposed to matters of the created order, the latter to matters of redemption.
Reformed Orthodoxy recognized the importance of natural theology, and Francis Turretin sheds light on its uses:
"Natural theology is useful to men, for we acknowledge its various ends and uses: (1) as a witness of the goodness of God towards sinners unworthy even of these remains of light (Acts 14:16, 17; Jn. 1:5); (2) as a bond of external discipline among men to prevent the world from becoming utterly corrupt (Rom. 2:14, 15); (3) as a subjective condition in man for the admission of the light of grace because God does not appeal to brutes and stocks, but to rational creatures; (4) as an incitement to the search for this more illustrious revelation (Acts 14:27); (5) to render men inexcusable (Rom. 1:20) both in this life, in the judgment of an accusing conscience (Rom. 2:15) and, in the future life, in the judgment which God shall judge concerning the secrets of men (Rom. 2:16)" (Institutes, I.1.4.4)
Item 1 speaks of what is commonly called "common grace." Through the motions of divine providence, God reveals Himself to every human being as the first cause of every creaturely benefit that he or she enjoys.
Item 2 refers to the subjection of every man to God's moral law (natural law implanted in every human heart) by which he discerns God's valuation of good and evil in various contexts and situations, inclined by conscience to choose the former and shun the latter. Though the depravity of man is such that the world is evidence of man having chosen evil most of the time, still it is not as debauched and sinfully convoluted as it can possibly be. Natural law maintains order in society inasmuch as man submits to it, directed and ordered by divine providence.
Item 3 makes much of the fact that man is man because man thinks, and is truly man when he thinks God's thoughts after Him. The intellectual faculties of man were created by God to be the means by which he apprehends God's truth as displayed in nature and salvation.
Item 4 builds on item 3 in that, seeing the wonders of God within himself and in the wonders of creation all around him through reason, man is then moved to seek the means by which he can be made right with God through faith.
Item 5 builds on item 4 in that men do not naturally go the extra mile from natural revelation to special revelation, and that this failure expresses itself continually, temporally, in a nagging conscience (the law accusing), and terminally, in the eschatological eventuality of hell.