In Lessing's play Nathan the Wise, Nathan is summoned by Muhammadan (Muslim) Saladin in order that Saladin might borrow money to continue fighting against the Crusader knights. Saladin wanted to unnerve Nathan and thereby put him at a disadvantage in the money lending negotiations, therefore he asked Nathan, who was also called "the Wise," to explain the paradox of there being three very different but self-attributed "true" religions. Saladin's paradox of course referred to Jewish, Christian, and Muhammadan (Islam) faiths.
To answer how three equally true yet different religions could exist, Nathan told the parable of the ring in which a father who loves all three sons equally gives each a copy of the authoritative family ring that bestows the right to rule upon the wearer. The moral of the parable was that in another time far removed from the time in the parable, the answer to the paradox would be fully revealed. The implication is that humankind's knowledge and capacity for knowledge are limited and imperfect, therefore one must do the best one can to rule justly and with compassion and love within one's own province. Nathan equated this parable with God's equal love for all people and God's expectation that all people live according to justice, mercy, compassion, kindness, and love.