@boagie,
... perhaps both definitions can fit into one dictionary
First, there's
The Truth - a metaphysical/spiritual/all-encompassing beast that we palpably feel in our very bones ... The Truth is out there ... we'll know it when we see it ... but, as BrightNoon implies, this is but religious faith.
Second, there's the truth
about - the truth about the roles with which this world discloses itself to us ... the truth about how we interact with those roles and disclose roles of our own to this world ... and the truth about how we carve out a life for ourselves in this world.
... or am I just rambling?