This is a possibility, not a fact. To date there is no evidence of extraterrestrial life. This page is an exercise in consistency, not a claim about what exists.
The criterion ignores the planet
If we ever discover sentient beings elsewhere in the universe, the same criterion would require their interests to be taken into account. The species line was never the right criterion, and the planetary one would not be either.
The symmetry test
By the principle of A10, "They're just animals", sentient extraterrestrials could be bred for food because they are not of our species. By the same rule, they could breed us. Almost no one accepts the second half, which shows the principle is not taken seriously.
The same goes for A2 and A11: if superiority or "what is normal for the species" decided, a more capable species would have a status above ours. Whoever rejects the conclusion is rejecting the premise.
How would we know
Probably with more difficulty than with animals, with whom we share an evolutionary kinship that helps interpret signs of pain. A very different mind may have no structure or behavior we recognize. Lack of resemblance to us would not be proof of an absence of experience.
How to decide under uncertainty. Instead of asking only "is this being sentient, yes or no?", ask how likely it is and weigh that by the size of the harm or benefit at stake. A moderate probability multiplied by an immense scale can outweigh a high certainty over small numbers. Uncertainty about a borderline case does not contaminate the certainty about the criterion: sentience is still what matters.
What this changes here and now
Almost nothing in practice, and that is exactly why the exercise is useful: with no personal interest at stake, it is easier to see that what would make us respect an unknown being is the capacity to feel, not appearance, intelligence or origin. That capacity already exists, here, in those we call animals.
Sources and further reading
- Veganismo Baseado em Evidências (Evidence-Based Veganism, in Portuguese), chapter 7
- The Moral Circle