19 because what may be known of God is manifest in them, for God has shown it to them.
19 because [in light of the fact that] what may be known of God
Verses 19 and 20 set forth what is known as “general revelation”; we can see theology in the created world. This awareness is available to all, Christian and non-Christian alike, even without the Word of God. God holds accountable all who reject His general revelation.
is manifest in them,
A knowledge of God is “manifest in them.” The word “manifest” means plain, evident. All creation shows clearly and visibly a certain knowledge of God. General revelation about God is common knowledge among men. Verse 20 will explain the process of how this is true.
The phrase “in them” means here among them. The context of revelation in creation argues for this interpretation. Knowledge of God by man is mediated through objective creation.
for God has shown it to them.
“Shown” is a term of revelation. Here it is God’s revelation in nature. God shows Himself in creation. People do not get this revelation by their innate ability, for we know God by what He chooses us to know; it is His initiative. We can know something of His “power and deity” (v. 20). Man acting on his own resourcefulness cannot know God.
People are culpable to general revelation.
Many people have never heard the gospel and some have never heard of Jesus. Their responsibility is to respond to the revelation they have. The revelation they have is God’s work in creation. That is not enough to become a Christian, but it shows a positive volition towards God. When they go positive in volition, then God will send missionaries to carry special revelation to them, for “how can they hear without a preacher?” (Ro 10:14). They are, therefore, without excuse if they reject revelation in creation (v.20).