I was teaching Jennifer Whiting's "Impersonal Friends" this morning—I love that piece—and I was going into the usual distinction between the fungible and nonfungible. I generally illustrate this with heirlooms. While money is fungible, the ring inherited from great grandmother is not: if the ring were swapped out for another just like it, it wouldn't be as good.
As I was teaching, though, I realized that that's too quick. Suppose that in the first place great grandmother instead had a different but similar ring and it was passed down through the generations to us. That would make no difference to anything that matters to us. So the ring is broadly fungible: it can be swapped for another ring with relevantly similar historical properties. The same seems true of all heirlooms.
But are persons fungible in the same way? Here's a thought. If something rightly matters a great deal to me it matters objectively at least somewhat. It rightly matters a great deal to me that I exist. It thus rightly matters a great deal to me that all of my history wasn't swapped for that of another similar individual. Therefore it matters objectively at least somewhat. Hence I am objectively not fungible even in that broader sense.