What did Paul mean here? There is more to it than just verse 17. Paul described the situation of the Jewish Christians in Corinth that still kept the Law and were blinded by it like a veil over their eyes with:
2 Cor 3:13 And not as Moses, which put a vail over his face, that the children of Israel could not stedfastly look to the end of that which is abolished: 14 But their minds were blinded: for until this day remaineth the same vail untaken away in the reading of the old testament; which vail is done away in Christ. 15 But even unto this day, when Moses is read, the vail is upon their heart. 16 Nevertheless when it shall turn to the Lord, the vail shall be taken away.
Now here is Paul’s explanation as to what happens when this veil is taken away and abolished.
17 Now the Lord is that Spirit: and where the Spirit of the Lord is, there is liberty.
That spirit, the spirit of the Lord is renewed vision, liberty a new life for such believers apart from such Law. That is what the Lord did for them. It is like they are born again without the veil, without the Law of slavery that prevented them from having a real hope of everlasting life. The abuse of this word spirit, or wind which it represents and making it out to be a person or something unearthly that inhabits human beings is sick. Like demon possession imbedded in our theology. Such thinking has no place in the faith. Paul did not do this as he went on to say:
18 But we all, with open face beholding as in a glass the glory of the Lord, are changed into the same image from glory to glory, even as by the Spirit of the Lord. 4:1 Therefore seeing we have this ministry, as we have received mercy, we faint not; 2 But have renounced the hidden things of dishonesty, not walking in craftiness, nor handling the word of God deceitfully; but by manifestation of the truth commending ourselves to every man’s conscience in the sight of God. 3 But if our gospel be hid, it is hid to them that are lost: 4 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.
These Jewish Corinthians to which Paul wrote here should now have an open face that reflects the glory of the Lord, even the spirit of the Lord though their ministry. The word of God such as the writings of Moses he described would no longer be handled deceitfully the way such Law keepers were still doing but by the manifestation so such truth that Christ died for us and freed us from this Law "commending ourselves to every man’s conscience in the sight of God." And of course the consequences that now visit those that do not believe. We can say then that: the light of the glorious gospel of Christ is that spirit.
Joseph