Speciesist Aliens Who Come to Earth
Imagine that it is the year 2012, alright so the year actually does not matter ... Aliens have made contact with us on earth, and they have tremendously superior technology and intellect(s). Although the aliens see that we have achieved plenty of variety in our tool use, they see us as highly primitive and 'a bit slow'. Because the gap between our highest intellect and theirs is so vast, our cute excursions into tool use do not make us seem terribly special to them. (You can assume they have met other species far more intelligent than us elsewhere at this point too if you would like). Furthermore, although we have learned to adapt many different environs to our needs, in many ways overcoming evolution, and achieving many other things, we live with a social structure that is incredibly flawed and, in their eyes, almost incompetent (insert any human failing or ineptitude here).
Because of this tremendous gap in intelligence, the aliens argue that they can do with us as they please (not a very intelligent thing for them to do you might argue. That is the point ... ;). Using this logic they enslave us and force us to work for them, fight and perform for their entertainment, and breed so that they may consume human milk and have more human offspring for their growing appetite for human flesh. Their next step is to begin farming humans more intensively putting us on a supplemented diet of different grains cooked as a hot cereal. That's all we get to eat. You might be thinking that you would commit suicide at this point (I wouldn't be able to take this oatmeal shlop for more than a week myself, so suicide seems appealing at this point); however, the aliens give us drugs to keep us alive both mentally and physically.
At this point, the thought experiment could go in many directions and carry on for much longer; however, the main point is covered before even getting into intensive farming of humans. There are certain questions that arrise because of this thought experiment:
Perhaps the most fundamental question that comes forward through this thought experiment has to do with what is (are) a relevant criterion (or criteria) for deciding how to address other species. What are the relevant criteria for how the aliens should treat us? What are the relevant criteria for how we should treat other species?
Many speciesists are completely comfortable asserting that we can use other animals because they are not as intelligent as us, by "us" they are referring to an ideal of humanity that excludes infants, most children, senile, elderly (with severe mental degeneration), and anyone with a severe mental disability. By intelligence they are referring to what human IQ tests test. This criterion is used in the thought experiment because it is so commonly used by humans as a criterion for separating us from other species. Basically anyone who is not capable of a certain level of abstract thought, reasoning, tool use, and a certain score on an IQ test is not wholly human from this viewpoint. That is not likely what someone proposing this is trying to focus on; however, that is what follows if you define humans (arbitrarily) based on intelligence. Of course it is not even a good way of defining humans or the value that humans have. If it were, Einstein would be more valuable than anyone reading this, and we would have to make a compelling case for why an infant or a severely mentally disabled person has any rights at all or at least equal rights to you or myself.
I will come back to this in the near future. I'm sure you can see where this is going however.