If a Tree Falls ...
Johannes' post on Phil Windley puts his finger on why defining "Digital Identity" is hard asserts that an identity is more than a set of claims.
If there is an entity, and there are no claims made about it, does it still have an identity?
If a tree falls in the forrest, and no one hears it, does it make a sound?
From a materialistic perspective, define "sound" and you've answered the second question. Define "identity" and you've answered the first.
This is why Dave and Timothy (and I, to some extent) are on a rant about ontology and semantics. You don't get definitions right, it's hard to have lucid thoughts, let alone unambiguious communications.
"Do identical twins have different identities even if we can't tell them apart?" Define what you mean by "identity" and I'll answer your question.
We can't even answer basic questions about the "things" we are talking about because we don't have common definitions of them. Convinced yet about the importance of a well defined ontology for the digital identity community?