1:21 knew God. Here Paul stresses that humanity not only has the opportunity to know God through general revelation, but that the revelation yields real knowledge. Humanity’s sin is the individual refusal to acknowledge what is already known to be true. While knowing God, people refuse to honor Him as God or give thanks to Him. The consequence of rejecting God was that their minds and hearts grew dark. A refusal to honor God leads all intellectual pursuits to frustration.