Natural Theology is the knowledge of God, as sovereign creator and judge, from nature, without special revelation. Man cannot know God as redeemer or discern the gospel from nature, nor many of His attributes, but man can know that God exists, is holy, righteous, wrathful against sin, etc. without having special revelation (Rom. 1:19-21). Therefore, all men are without excuse in the Day of Judgment for not glorifying Him as God, and for sinning against Him (cf. Rev. 20:12).

“Although the light of nature, and the works of creation and providence, do so far manifest the goodness, wisdom, and power of God, as to leave men inexcusable (Psa 19:1-3; Rom 1:19-20; 1:32 with Rom. 2:1; 2:14-15); yet are they not sufficient to give that knowledge of God, and of his will, which is necessary unto salvation (1 Cor 1:21; 2:13-14); therefore it pleased the Lord, at sundry times, and in divers manners, to reveal himself, and to declare that his will unto his Church (Heb 1:1); and afterwards, for the better preserving and propagating of the truth, and for the more sure establishment and comfort of the Church against the corruption of the flesh, and the malice of Satan and of the world, to commit the same wholly unto writing (Prov 22:19-21; Isa 8:19-20; Mat 4:4, 7, 10; Luke 1:3-4; Rom 15:4); which maketh the holy Scripture to be most necessary (2 Tim 3:15; 2 Pet 1:19); those former ways of God’s revealing his will unto his people being now ceased (Heb 1:1-2).”

Westminster Confession of Faith 1:1.

There are four ways people can know about God without having read the Scriptures: from creation, ordinary providence, the extraordinary works of God, and from their own conscience. Natural Theology is therefore partly innate, in our hearts, and partly acquired externally from creation and providence (cf. Turretin, Institutes, 1.3.4).

“Nations without the visible church never wanted means, either ordinary or extraordinary, to know God; though we cannot in reason say that the decree or law of an heathen king is the Arminian universal grace, yet some means all have. And God has laid open four books to all nations:

1. That book of creation of the heavens and his work (Psa. 19:1); the heavens do book, and register the glory of God (Rom. 1:20).

2. The book of ordinary providence is a chronicle or diurnal [i.e. daily reminder] of the Godhead, and a testimony that there is a God (Acts 14:17; 17:27).

3. There is a book of the extraordinary works of God, and some report of the true God, upon occasion carried to nations without the borders of the visible church. As our text says [“who hath delivered Daniel from the power of the lions” (Daniel 6:27)], and Rahab says (Josh. 2:10), “We have heard how the Lord dried up the Red Sea”, etc. But as children sport themselves and play with the pictures in a book, and with the gold on the covering of the book, and the ribbons, not knowing the sense and meaning of this book, so do we sport ourselves in looking on the outside of these three books, not searching in to read and understand “the invisible things of God, his eternal power and Godhead” (Rom. 1:20).

4. The book of man’s conscience (Rom. 2:14-15), speaks of God, to all nations, though now by reason of our sinful blindness and dullness, that book is uncorrected, and dimly printed, written with white and watery ink, so that we see not God distinctly in it. Yet all these four serve to make men “without excuse, because, when they know God, they glorify him not as God, neither are thankful” (Rom. 1:20), but this condemns us to whom there is laid open a better and fairer and more learned piece (Ps. 19:7).”

Samuel Rutherford, Sermons Preached before the English Houses of Parliament by the Scottish Commissioners to the Westminster Assembly of Divines, 1643–1645, pp. 400-401.

Having seen these four ways God reveals Himself in Nature, we may ask what can be known about God from Natural Theology. Stephen Charnock lists ten attributes of God that may be recognized by the light of Nature:

1. the power of God, in creating a world out of nothing
2. the wisdom of God, in the order, variety, and beauty of creation
3. the goodness of God, in the provision God makes for His creatures
4. the immutability of God, for if He were mutable, He would lack the perfection of the sun and heavenly bodies, “wherein no change hath been observed”
5. His eternity, for He must exist before what is made in time
6. the omniscience of God, since as the Creator He must necessarily know everything He has made
7. the sovereignty of God, “in the obedience his creatures pay to him, in observing their several orders, and moving in the spheres wherein he set them”
8. the spirituality of God, insofar as God is not visible, “and the more spiritual any creature in the world is, the more pure it is”
9. the sufficiency ofGod, for He gave all creatures a beginning, and so their being was not necessary, which means God was in no need of them
10. His majesty, seen in the glory of the heavens

All of these attributes of God may be known by sinful man by observation of the natural world.

Charnock, The Knowledge of God, in Works, 4:115; cited from Beeke, Jones, A Puritan Theology, p. 17.

While the gospel may not reach every individual person in their lifetime, everyone is without excuse for sinning against the light God did give them in these four books.

“Because that which may be known of God is manifest in them; for God hath shewed it unto them. For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse: Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened” (Romans 1:19-21).

“And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works” (Revelation 20:12).