Are you looking for some philosophical principle or just a definition? If the latter, here:
Merriam-Webster defines cannibalism as:
1 : the usually ritualistic eating of human flesh by a human being 2 : the eating of the flesh of an animal by another animal of the same kind
“Kind” is obviously vague. Human is defined as:
a bipedal primate mammal (Homo sapiens: MAN ; broadly : HOMINID)
According to Dictionary.com, Random House defines cannibalism as:
1. the eating of human flesh by another human being,
2. the eating of the flesh of an animal by another animal of its own kind.
3. the ceremonial eating of human flesh or parts of the human body for magical or religious purposes, as to acquire the power or skill of a person recently killed.
while The American Heritage Dictionary has it as a derived form of
cannibal: 1. A person who eats the flesh of other humans. 2. An animal that feeds on others of its own kind.
Again, “kind” is of no help. For human we find according to Random House:
**1. of, pertaining to, characteristic of, or having the nature of people: human frailty.
2. consisting of people: the human race. **
and
5. a human being.
which leads us to
**human being
- any individual of the genus Homo, esp. a member of the species Homo sapiens.
- a person, esp. as distinguished from other animals or as representing the human species: living conditions not fit for human beings; a very generous human being.**
and according to The American Heritage Dictionary:
**human
- A member of the genus Homo and especially of the species H. sapiens.
- A person: the extraordinary humans who explored Antarctica.**
Looking up person, we find
1. a human being, whether man, woman, or child: The table seats four persons.
2. a human being as distinguished from an animal or a thing. [Random House]
and
A living human. Often used in combination: chairperson; spokesperson; salesperson. [American Heritage]
So there you go.
Only relevant definitions provided.