ISB ~ Romans 1 v20

his invisible nature:Paul contends that our minds can rise to a knowledge of God’s power and divinity by reflecting on the grandeur of the world (Wis 13:5; Acts 17:2628). Failure to do this is inexcusable since God has made it possible everywhere and at all times (CCC 1147). Atheism and idolatry are thus moral problems and only secondarily intellectual problems (CCC 2125).

• Vatican I decreed in 1870 that God’s existence can be known with certainty by the light of human reason (Dei Fiiius, chap. 2). This confirmed centuries of theological tradition, which developed numerous philosophical arguments for the existence of one Supreme Being (CCC 3135).