And children have more dignity than dogs, because humans are worthy of more honor than dogs are. The humane society gathers up stray dogs and mercifully puts some of them to sleep. But nobody would let them do that with children. So dignity means worthiness of honor. Christ has infinite dignity as the Son of God.
Eternity means forever.
Something that has eternity has no beginning and no ending. If something lasts for a while and stops, it does not have eternity. If something didn't exist for a long time and then it was created or came into being, it doesn't have eternity. No beginning and no ending. Purity means unsoiled, not dirty.