hypothesis: Eating is immoral without natural teleology and an order of being.
Eating requires killing life forms. This can only be moral if it is a case of using the life form appropriately, but to do so requires its very existence is ordered to another’s use.* Absent this, eating is simply a matter of might makes right.
Objection: If the very existence of something was ordered to our use, being eaten is one of its fulfillments. But what we observe is everything trying to preserve itself. Gazelles run away and plants develop pesticides. They don’t offer themselves or some of their number for the use of others.
Objection: Morality is species-relative, e.g. whether cannibalism, abandonment of children, sterilization, etc. are contrary to flourishing depend on the animal in question. We cannot assume an extra-species morality to judge the action of one species on another.
*We’re setting aside utilitarian justifications, though they can be viewed as consistent with this account.