This seems plausible:
- All purely material objects are fungible.
- No persons are fungible.
- So, no persons are purely material objects.
Maybe that's not quite right. One might think that some objects care about (a colleague gave the examples of the Mona Lisa and Grandpa's Bible) are non-fungible. But I think it's plausible that material objects are at most derivatively non-fungible, deriving their non-fungibility from the non-fungibility of people. Thus:
- No purely material object is non-derivately non-fungible.
- Every person is non-derivatively non-fungible.
- So, no person is a purely material object.