The only permanent truth, is not even Torah and Mitzvos, rather the REASON behind Torah and Mitzvos (for even a mitzvah is abrogated if a prophet says to (temporarily) do something different) and the reason behind Torah and Mitzvos is the following: we humans are comprised of two opposing instincts, goodness and evil! (or love and anger/hate!) in order for our goodness to overcome our evil, we must submit to the instructions of a being, Who Only Contains Goodness!