He is setting the stage for something here. He is going to make a comparison between one group of people and another group of people—those who are mature and those who are not, those who are converted and those who are not converted.
They did not realize He was the God of creation. They did not realize He was the Savior. They could not discern the things that He was saying and doing. They did not put them in the right context. They did not understand what He was doing and saying from the right perspective.
The word "mystery" is not the same as our English usage of the word mystery. (Remember this was written in the Greek.) Mystery to the Greek meant not a puzzle that was difficult to solve, but a secret impossible to penetrate. Mystery to them was something that was hidden; it was unintelligible to those who were not initiated, as into a secret society or as into a religion.
Most of you have heard of the mystery religions. What they did was unintelligible to those who were on the outside, but to those who were on the inside, it made clear sense to them—what was being said or enacted in their ritual or whatever it was they were doing.
That is what we are dealing with here. It was a secret impossible to penetrate, not a puzzle that was difficult to solve. What is crystal clear to those who were on the inside was unintelligible to those who were on the outside.
In like manner, to those who have received the Spirit of God, the Holy Spirit has joined with the spirit in man and it has added a dimension to man's life that he previously did not have. So then, things that are crystal clear to him are unintelligible to those who do not have this added dimension. We find that it (meaning the things of the Spirit) have been revealed by God.
If mankind had seen Christ, if they had clearly identified with Him, the history of the world would be exceedingly different. But they did not see because, as Paul writes here, they were not mature. Mature, in this context, means converted. It does not always mean exactly that, but in this context it does. There is a contrast between those who are able to see and those who are not able to see. And, those who are able to see are, in this context, those who are mature.
Even though Christ quoted - and lived - the scriptures that many in His audience were clearly familiar with, they did not see God working through Him. This is the way that it has always been with God's servants. Christ was not the only one. Christ Himself testified that those people killed the prophets. Now, I think that they would not have killed the prophets if they clearly saw them as being messengers from God. If they clearly believed in God and were fearful of His authority over His creation, His governance of it, they would not have dared to have done that! That is the way it has always been - there are those who see and there are those who do not see.
Paul testifies here that people are looking into a mystery. This mystery is not a puzzle that is difficult to solve, but a secret impossible to penetrate. So the world, as a result, is not all there upstairs. So it accepts its own and rejects the truths of God.
