2 Corinthians 4:1-6

v1-2: Those who preach the gospel, whether they be ministers or not, are to be marked by sincerity and faithfulness. In their methods they are not to act deceptively or in underhanded ways.  In their message they are not to distort the word of God.

v3-4: The devil keeps people from seeing the light of the glory of God revealed through Christ in the gospel.  He "darkens people's minds, increases their prejudices, and supports his influence by keeping them in the dark, blinding their minds with ignorance, error, and prejudices."

v5-6: Lost people do not need to hear our "own ideas and private opinions" but Christ preached, for He alone is the Saviour of sinners as well as the Lord of all.  It is through preaching Christ that the light of the knowledge of the glory of God comes to them.