For now we see in a mirror dimly, but then face to face (πρόσωπον πρὸς πρόσωπον prosopon pros prosopon); now I know in part, but then I will know fully just as I also have been fully known.
This is a very enigmatic verse, I think possibly one of the verses Peter had in mind when he said of Paul's Epsitles:
"...in which are some things hard to understand..." 2 Peter 3:16
My opinion is that the key to unlocking the passage is to understand what πρόσωπον πρὸς πρόσωπον (prosopon pros prosopon) means.
This phrase is a direct translation from the the Hebrew פנים אל־פנים (panim al panim) which occurs in these OT verses:
ויקרא יעקב שם המקום פניאל כי ראיתי אלהים פנים אל פנים ותנצל נפשי
So Jacob named the place Peniel (פניאל face of God), for he said, “I have seen God face to face (פנים אל פנים panim al panim), yet my life has been preserved Gen 32:30
וירא גדעון כי מלאך יהוה הוא ויאמר גדעון אהה אדני יהוה--כי על כן ראיתי מלאך יהוה פנים אל פנים
When Gideon saw that he was the angel of the LORD, he said, "Alas, O Lord GOD! For now I have seen the angel of the LORD face to face (פנים אל פנים panim al panim)." Judges 6:22
Thus πρόσωπον πρὸς πρόσωπον means "to see God face to face" i.e., to discern perfectly God's nature, will, and purposes (Thayer's Lexicon).
So how can we "discern perfectly God's nature, will, and purposes"?
The key is in the previous three verses of 1 Cor 13:
9Love never fails; but if there are gifts of prophecy, they will be done away; if there are tongues, they will cease; if there is knowledge, it will be done away. 9For we know in part and we prophesy in part; 10but when the perfect comes, the partial will be done away. 11When I was a child, I used to speak like a child, think like a child, reason like a child; when I became a man, I did away with childish things.
This passage means that the temporary spiritual gifts of prophecy, tongues, knowledge, etc. which were only needed to confirm the New Testament revelation (Heb 2:1-4) would be done away when "the perfect" comes. The perfect is the completed canon of scripture, Old Testament and New Testament.
Thus with the completed canon we have the potential to see God πρόσωπον πρὸς πρόσωπον (prosopon pros prosopon) פנים אל פנים (panim al panim) or face to face, to know him fully, just as fully as we have been known by Him (and He is omniscient)--because He has made full and complete revelation of Himself through his completed canon of scripture, the Bible.
Additionally, this is the same thought Peter is expressing here:
For by these He has granted to us His precious and magnificent promises, so that by them you may become partakers of the divine nature... (2 Peter 1:4)
