John 2

John2:23Now while he was in Jerusalem at the Passover Feast, many people saw the miraculous signs he was doing and believed in his name.
John2:24But Jesus would not entrust himself to them, for he knew all men.
John2:25He did not need man's testimony about man, for he knew what was in a man.

There were two questions coming up when I read this:
1. How did he know? (well, not really a question but an interesting point)
2. What was in a "man"?

1. Actually a very simple question. If we presume that God is almighty, then Jesus is almighty as well (since Jesus is God) and since an almighty person/man knows everything, Jesus also knows "all men".
Heb.4:13Nothing in all creation is hidden from God's sight. Everything is uncovered and laid bare before the eyes of him to whom we must give account.

Another explanation:
1. Cor.2:11For who among men knows the thoughts of a man except the man's spirit within him?
And because God has come down to earth as a human being(John1,1+14; Phil.2:6) he was able to experience/know what the thoughts of man are.
Heb.4:15 For we do not have a high priest who is unable to sympathize with our weaknesses, but we have one who has been tempted in every way, just as we are—yet was without sin.

2. What is in a man? What did Jesus see in the men at that time?
If we have a look at what Jesus did when he was in Jerusalem for Passover we might be able to figure out what were the thoughts of the people at that time.
When Jesus went up to Jerusalem he found men selling goods in the temple - in the house of his father.
Then later when the Jews asked him what sign he can show them to prove that he has the authority to clear the temple he answered: "Destroy this temple, and I will raise it again in three days." But the reply was full of ignorance and lack of understanding:"It has taken forty-six years to build this temple, and you are going to raise it in three days?"
However in verse 23 many people who saw the miraculous signs he was doing believed in him. Believing because of seeing... can we call this "faith"?? Or "believing"??
Be it as it may, Jesus has seen several characteristics of the men at that time:
- the greed and the desires of them (=> selling goods in the house of God =>money!)
- the ignorance and lack of understanding (=> they did not understand what Jesus was talking about and they later also made use of this statement to mock Jesus when he was on the cross Mk.15:29-30)
- the short-term faith which was based on the "seeing, then believing" principle
These are the attitudes of man which Jesus saw when he was in Jerusalem. Of course Jesus knew a lot more about them, but I think that the things listed above are included in the things Jesus knew. That was in "man".