For we are not writing to you anything other than what you read and understand, and I hope you will fully understand— just as you did partially understand us—that on the day of our Master [Lord] Jesus you will boast of us as we will boast of you. 
(2 Corinthians 1:13-14)
We hear a lot about seeing the “big picture”. The Apostle Paul clearly got that. He realized it is easy to see the details. It is hard to see what he calls the “whole picture”. There is a difference, however, between the big picture and the whole picture. It is an enormous difference.
God’s word, and the insight of the Holy Spirit, gives us the whole picture. The truth, the clear truth, helps us see the whole picture.
- May I see the whole picture.
- May I see it today and every day.
Paul means exactly what we read in his letters, as follows from candor and sincerity. (“You … read” has a collective sense, because one person would be reading to the assembled others.)
God is good: God wants us to understand. God does not delight in confusion at all. God is good to give us the resources to help us understand. God is in a good mood.
“Or also understand” makes their understanding of what they read an alternative to their reading, as though they might not be understanding everything, they read in his letters to them.
Highlighting this possibility are
- a Greek wordplay between anaginōskete (“you read”) and epiginōskete (“you understand”) and
- the contrast between Paul’s hoping that the Corinthians will “understand completely” and
- their having “understood partly”
- What he hopes they’ll understand completely is that they already have Paul to be proud of for his having evangelized them (“your basis for boasting”), just as “on the Day of the Master, Jesus” (when he comes back as Lord for the Last Judgment)
Paul will have them to be proud of as his converts. “Indeed” accents his having them as a basis for boasting and thus continues his fence-mending with the Corinthians.
Good news: We can understand completely. God gives the Holy Spirit and wisdom. We just must ask God and have faith.
 The Holy Bible: English Standard Version. (2016). (2 Co 1:13–14). Wheaton, IL: Crossway Bibles.
 Gundry, R. H. (2010). Commentary on the New Testament: Verse-by-Verse Explanations with a Literal Translation (p. 691). Peabody, MA: Hendrickson Publishers.