He then gave them the key to the understanding of the scriptures. In the midst of their conversation, Jesus suddenly appeared, throwing the group into a state of panic. They thought he was a ghost, even though they had just been talking about his appearance to Peter. Peace is the tranquility of order. It is true security.
True security is the direct consequence of divine union.
There is nothing wrong with desiring security. Everybody wants it and needs it. The problem is that we look for it in the wrong places. Peace is the treasure that Jesus triumphantly and joyfully bestows, or tries to bestow, on his crushed and demoralized apostles. But these words made no impression on them because they were preoccupied with the fear that they might be seized and put in jail as his disciples.