There are lots of good reasons to write alien characters, and they have to do with human beings. Let's take a look at how we hold up aliens as mirrors to our own face.

Reasons to Put Aliens in Our Stories

Social criticism can come across as less preachy and more palatable if the story is about intolerant, bigoted people with funny foreheads instead of folks who look like us. One example is the Star Trek TNG episode "Chain of Command", in which Captain Picard is captured and tortured by a Cardassian. At one point, Picard says to his captor, "Torture has never been a reliable means of extracting information... Whenever I look at you now... I will see a six-year old boy who is powerless to protect himself... In spite of all you have done to me, I find you a pitiable man." Voicing these lines, actor Patrick Stewart was clearly speaking from his personal passion for universal human rights and commitment to Amnesty International. The Cardassian was a stand-in for human torturers; the message was about the reasons for and futility of torture on earth.

Just as aliens can be stand-ins for humans we want to criticize, they can also personify the people we fear. During the Cold War, some SF took a xenophobic turn. Going back to one of the first fantastic novels, Bram Stoker's Dracula is about an entity that is Continental, lives under an absolute monarchist regime, and is not subject to natural law and rational explanation. This entity emasculates nice English men and seduces pure English women. The novel can be read as an exploration of everything upper-class English men most feared in the late 19th century.

Aliens can be mirrors; they can also be like film negatives, giving us a definition of our humanity through omission. In the original Star Trek, the Vulcan Spock's presence provided commentary on the emotional weakness and strength of humans. In TNG, the android Data performs a similar fucntion. C.J. Cherryh's atevi, in her series of novels beginning with Foreigner, lack the human ability to "like," but they possess "manchi" and form associations -- sort of but not exactly like having "loyalty" and "friendship." The translator protagonist struggles to maintain his own humanity while immersed in a nonhuman culture.

Alien characters also shed light on the human condition by interacting with humans. The interaction can be a comedy of errors and misunderstandings, or it can be tragic. Interaction can be cultural, economic, intellectual, erotic, or biological. It can explore the difficulties inherent in diversity as well as the opportunities diversity presents, certainly a theme of omnipresent importance in our world.

So we have lots of good reasons to write about aliens. Now, how do we write them well?

How to Write Aliens Well

In a bad role-playing adventure, the characters enter a cave complex or abandoned building. There's nothing to eat and nowhere to get bags of gold, or to spend it. Nonetheless, the characters encounter scores of critters carrying treasure.

Don't do this!

Aliens' culture and psychology should arise from their ecology. Why? Because our own frame of reference has been shaped by the conditions of our survival. To write alien characters that effectively mirror, counterpoint, or interact with us, they must be as richly developed as we are. Let's look at some examples of aliens done right.

Returning to C.J. Cherryh's atevi, human Bren Cameron understands them on a gut level when he rides a mechieti in a herd of mechieti and physically feels the animals' fierce desire to cleave to their leader. Atevi differ from humans because of biological hardwiring, a genetic divergence that occurred early in the history of life on the planet. Likewise, Diane Duane's Star Trek novel Spock's World roots Vulcan culture and philosophy in the distant past and the planetary environment.

Now let's think about our own aliens. Are we writing bulge-nosed slimetoads because they're cool, man!, or are we writing with a deeper literary purpose? Here are some questions to ask ourselves:

1. If our aliens were human characters, would the story be the same? If so, then perhaps the aliens should be humans. Maybe the story doesn't need to be science fiction.
   
   
2. If alien characters are essential to the story, then what function do they perform in the story, and is this the role you want them to play? For instance, if we want to explore the importance of dream sleep in making us who we are, our aliens could be a species that doesn't dream. Our plot would present a conflict that allows us to explore the psychology of a species that lacks unconscious hallucinations and, by contrast, our own psychology.
   
   
3. Assuming the aliens' differences are important to the story, then let's consider why are they different from humans. If, for example, our aliens don't dream, then why don't they dream? Now we should speculate on why we have biological hardwiring that makes us dream; and why either another sentient species wouldn't have evolved similarly, or their culture uses technology to suppress dreaming, or...
   
   
4. We know why our aliens differ from us. Now let's explore the wider ramifications. We've already determined that their difference is critical to the plot of our story, but these people don't exist just to have our plot happen to them. They were living lives before our story started and, if they survive, will go on living after our story ends. Our non-dreaming aliens: Do they accept waking hallucinations -- what we'd call schizophrenia -- as normal? How then do they express religious beliefs? How do family members, who can't drop their emotional baggage at night, relate to each other? If families are structured differently, then how are children raised, are people settled or nomadic, how does the economy work...?
   
   
5. Now that we've worked out our aliens in detail and in depth, do they still work in our story? Does our story still work for them? We'll go back to Step #1 and run through the questions again, to make sure all our story elements still make sense.

And voila, or as the Whooziwhats of Wherefore say, zgaphut -- we have strong alien characters who have a reason to be in our story and a life outside it. Oh go ahead, make 'em slimy and green if you want to, as long as it makes sense!