Not Believing In God Is Denying Evidence.

Observe what they knew: The invisible things of him, even his eternal power and Godhead. Though God be not the object of sense, yet he hath discovered and made known himself by those things that are sensible. The power and Godhead of God are invisible things, and yet are clearly seen in their products. He works in secret Ecclesiastes 5, but manifests what he has wrought, and therein makes known his power and Godhead, and others of his attributes which natural light apprehends in the idea of a God. They could not come by natural light to the knowledge of the three persons in the Godhead (though some fancy they have found footsteps of this in Plato's writings), but they did come to the knowledge of the Godhead, at least so much knowledge as was sufficient to have kept them from idolatry. This was that truth which they held in unrighteousness.

How they knew it: By the things that are made, which could not make themselves, nor fall into such an exact order and harmony by any casual hits and therefore must have been produced by some first cause or intelligent agent, which first cause could be no other than an eternal powerful God. See Isaiah 26, Acts 24. The workman is known by his work. The variety, multitude, order, beauty, harmony, different nature, and excellent contrivance, of the things that are made, the direction of them to certain ends, and the concurrence of all the parts to the good and beauty of the whole, do abundantly prove a Creator and his eternal power and Godhead. Thus did the light shine in the darkness. And this from the creation of the world.

Understand it either as the topic from which the knowledge of them is drawn. To evince this truth, we have recourse to the great work of creation. And some think this ktisis kosmou, this creature of the world (as it may be read), is to be understood of man, the ktisis kat exochen--the most remarkable creature of the lower world, called ktisis, Mark 16:15. The frame and structure of human bodies, and especially the most excellent powers, faculties, and capacities of human souls, do abundantly prove that there is a Creator, and that he is God.

Or, As the date of the discovery. It as old as the creation of the world. In this sense apo ktiseos is most frequently used in scripture. These notices concerning God are not any modern discoveries, hit upon of late, but ancient truths, which were from the beginning. The way of the acknowledgement of God is a good old way it was from the beginning. Truth got the start of error. - Matthew Henry