Chapter 5 - Knowledge of God shines forth in the fashioning of the universe and the continuing government of it
Section 13-15 - Persistent in error, we are without excuse
Section 13 - The Holy Spirit rejects all cults contrived by men
We wrongly follow our own opinions in deciding what kind of god to worship (1 Cor 10:20; ePH 2:12-13; Rom 1:21; Habakkuk 2:18, 20; John 4:22).
Even the princes of this world do not understand the wisdom of God (1 Cor 2:8; Acts 17:23).
Section 14 - The manifestation of God in nature speaks to us in vain
because "we have not the eyes to see this unless they be illlumined by the inner revelation of God through faith." (Heb 11:3; Rom 1:19; Acts 17:27; 14:16-17).
Section 15 - We have no excuse
because "the fault of dullness is within us."
We can't claim deafness to God's voice in nature, when mute creatures proclaim it.