Assuming we are able to begin colonizing space beyond our solar system on a large scale, would it be morally justified and economically effective for humanity to enslave alien, i.e. non-human, species, even those that have achieved human levels of sentience?
Would it be more militarily effective to wipe them out, as slavery could pose a security threat (i.e. slave riots)? Would it be more economically effective to use automation or free labor as opposed to non-human slave labor (considering the question of security costs and the role of incentives).