Okay, we all know what this one is: hitherto unknown space-faring
civilisation discovers the Earth, alien ships descend from the skies,
out belch green-skinned armies of destruction wielding ray cannons
and humanity is in for a generally hard time.
This field is so ploughed over that the bedrock has got ruts cut in it
a foot deep. Ever since H. G. Wells sprang a Martian invasion on
us in 1898 the front runner for setbacks in man's march into the
future has been visits by unfriendly extraterrestrials with designs on
our world. Uh, huh. Yeah. Been there. Done
For something that is firmly in the realm of fantasy, the notion of
alien invaders can produce some very definite opinions and after a hundred years, the topic
has split neatly into three camps. First, there are the popular science
writers of the Asimov, Clarke, Sagan camp who frame aliens in the
angelic template without an aggressive bone (if they have bones) in
their bodies. They tend to point out that anyone who had reached
a level of development where they are capable of waging interstellar
war will have got beyond war and will be terribly peaceful. Yes,
technological advancement as the touchstone of benign intent.
Yep. Nazi Germany and the Soviet Union proved that one right.
Then there are the writers of science fiction who have a more
realistic approach–at least as far as motives go. Though it
was generally for dramatic purposes, sci-fi understood that there
isn't much of any link between how powerful and how moral you are.
In fact, their instinctive approach of ascribing human motives to
alien invaders is probably closer to the truth in that they assume
that reason is a universal quality rather than a human invention and
is therefore similar throughout space and time. C. S. Lewis even
took this a step further in
Out of the Silent Planet
Martians who were peaceful, not because they had evolved into it, but
because they had never shared the Fall which has been causing so much
grief on Earth since that little incident in Eden.
Finally, there are those who claim that the aliens are already here
and giving us anal probes.