If you had a peaceful extra-terrestrial encounter, what would you want the aliens to be like? What kind of alien would make you understand the purpose of life?
Think carefully. This is peaceful, which means the aliens are not in any way trying to hurt you or Earth. (But they could, out of kindness or misunderstanding. If you've ever read Speaker for the Dead, there's a good example in that book of how what is highest honor to one species could be death to another.)
Would you be moved by the one-ness of life if the aliens were humanoid like us? If they had legs and arms and heads and made noises to communicate and saw in the visible spectrum with eyes? Would it fill you with a sense of understanding about the order of things in the universe?
Or, would you think it was more beautiful if they were completely different? What if they're not even made of carbon? Could they be metallic? Or silicates? Would you decide that humans are truly special and unique, and be thankful that chance (or God, I suppose) allowed us to be the way we are? Would you collapse at the feet of entropy?
Maybe you would see the aliens and realize just how unevolved we are. Maybe they are near-perfect machines. Maybe they aren't machines at all - maybe their bodies are useless and their brains are everything. Maybe they don't even have bodies.
What would you want their senses to be? Do you wish they could see in the visible spectrum so you could take them to your favorite place and show them how beautiful Earth is? Do you wish they saw in x-ray or infrared or something else, so they could tell you about the world you can't see? Should they be able to hear sound? Should they have sense we don't have? What if they feel cosmic rays pounding through their bodies? What if they feel emotions like we feel force?
What do you want them to think about us? Should they marvel at us? Should they be disgusted? Should they be confused? Why?
What would you say to the alien? What would you tell them about Earth?
Earth is the sacred and the profane. We are children of paradox.