Pros and Cons
Argument:
- Aliens exist somewhere and/or have come to Earth at some point in history.
Pros:
- They don't seem to have wiped us out.
- Maybe there is still technology or some higher stage of evolution.
- Life exists elsewhere in the universe.
Cons:
- Might amount to looking for a god, a kind of religion.
- They aren't here en-mass, might say something about the difficulty of space travel.
- They aren't communicating, maybe we're radically different from them.
- No evidence of their existence.
- Results in a prodigious amount of speculation.