I was blind, but now I see. There is physical blindness, and there is spiritual blindness.

"But if our gospel be hid, it is hid to them that are lost: in whom the god of this world hath blinded the minds of them which believe not, lest the light of the glorious gospel of Christ, who is the image of God, should shine unto them." - 2 Corinthians 4:3-4

Paul was struck with physical blindness for three days after Jesus spoke to him in a vision. Jesus appeared to Paul to send him as a minister of the gospel to open peoples eyes that were spiritually blind.

"And I said, Who art thou, Lord? And he said, I am Jesus whom thou persecutest. But rise, and stand upon thy feet: for I have appeared unto thee for this purpose, to make thee a minister and a witness both of these things which thou hast seen, and of those things in the which I will appear unto thee; delivering thee from the people, and from the Gentiles, unto whom now I send thee, to open their eyes, and to turn them from darkness to light, and from the power of Satan unto God, that they may receive forgiveness of sins, and inheritance among them which are sanctified by faith that is in me." - Acts 26:15-18

Paul preached the same gospel as was preached on the Day of Pentecost.

"Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.

“For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call. And with many other words did he testify and exhort, saying, Save yourselves from this untoward generation.

“Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls. And they continued stedfastly in the apostles' doctrine and fellowship, and in breaking of bread, and in prayers. ... praising God, and having favour with all the people. And the Lord added to the church daily such as should be saved." - Acts 2:38-42, 47