It’s possible that the civilization is not alive anymore, but it did send out a spacecraft. We ourselves sent out Voyager I and Voyager II. There could be a lot of equipment out there. The point is that this is the very first object we found from outside the solar system. It is very similar to when I walk on the beach with my daughter and look at the seashells that are swept ashore. Every now and then we find an object of artificial origin. And this could be a message in a bottle, and we should be open-minded. So we put this sentence in the paper.

we need to consider the possibility that ‘Oumuamua was sent by aliens, the dangers of unscientific speculation, and what belief in an advanced extraterrestrial civilization has in common with faith in God.