What we do not know is difficult to quantify and it is how we are that we try to. A truly smart person is the person smart enough to know how stupid they are and if that is true then I must be highly intelligent. If the South Node is what we do know then the North Node is what we do not know. Each of the houses the nodes are in show the area of life of what we know/don't know.
Elizabeth Spring has a wonderful site about the Nodes of the Moon by the way.
Since the 12th is about the unconscious and the collection unconsious, magic and deeper realms not reached by reason, then it stands that my North Node cannot be reached by reason or thinking about logically. Darn. As much as I want to connect the dots here it is not possible for me to do so it seems. However nodes still help me when doing the charts of other people.
My joy is in doing creative things so there is 12th house Nodes and Venus. They've got to do their secret and hidden 12th house things as this house symbolizes. Sometimes truth is not being smart, but rather just listening for the high notes.