Note that this has to do with knowing Christ, not knowing about Him. This is about hearing His voice and communing with Him and being taught by Him. It is about allowing the Holy Spirit to give you a new mind, the mind of Christ. The human mind was never created to be used outside of a submissive relationship with God, but rather to be in submission to the Holy Spirit. Knowing God and standing in His presence in submission is the source of all holiness.

Ephesians 4:20 But ye have not so learned Christ;

Ephesians 4:21 If so be that ye have heard him, and have been taught by him, as the truth is in Jesus:

Ephesians 4:22 That ye put off concerning the former conversation the old man, which is corrupt according to the deceitful lusts;

Ephesians 4:23 And be renewed in the spirit of your mind;

Ephesians 4:24 And that ye put on the new man, which after God is created in righteousness and true holiness.