Answer

Geovanni.

We have received no intelligent-type radio signals.
We have no physical evidence for extra-solar intelligent life.
(If there was intelligent extra-solar life, we would've gotten radio signals or physical evidence.)
There is probably no other intelligent life in the universe.

Katie.

We haven't visited any other solar systems to check if there's intelligent life there.
(You would have to visit another solar system in order to know if there's intelligent life there or not.)
There is intelligent life in some other solar system.

Katie is giving an opposing argument because she doesn't address Giovanni's premises.

In my view, each of these arguments has burden of proof problems.

Giovanni's argument sets an irrational standard for the possibility of extra-solar life. The universe is so big that billions of years could pass before radio signals from another civilization could reach us, and when they did, they would be so faint as to be undetectable.

Katie's argument sets a false burden of proof on the negative side. Just because no one has proved that each individual other solar system is bereft of intelligent life doesn't mean that any of those solar systems actually contain intelligent life.

Independently of these arguments, I think a good argument could be made for the existence of extra-solar intelligent life based on the size and general properties of the universe, but Katie does not make this argument. She makes a false burden of proof argument, and so the argument she actually gives is a bad one.

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