Answer: The very light of nature in man, and the works of God₁, declare plainly that there is a God; but his Word and Spirit only do sufficiently and effectually reveal him unto men for their salvation₂.

1. Romans 1:19-20; Psalm 19:1-3; Acts 17:28
2. 1 Cor 2:9-10; 2 Tim 3:15-17; Isa 59:21

For further study see:

1. Dr. Kenneth G. Talbot explains WLC 2 (part 1)
   
2. Dr. Kenneth G. Talbot explains WLC 2 (part 2)