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Full Idea
The Identity of Indiscernibles is not a necessary truth. It fails in possible worlds where there are two identical spheres in a non-absolute space, or worlds without beginning or end where events are exactly cyclically repeated.
Clarification
The principle (associated with Leibniz) claims that if two things can't be distinguished they are the same
Gist of Idea
Two pure spheres in non-absolute space are identical but indiscernible
Source
Keith Campbell (The Metaphysic of Abstract Particulars [1981], §5)
Book Ref
'Properties', ed/tr. Mellor,D.H. /Oliver,A [OUP 1997], p.132
A Reaction
The principle was always very suspect, and these seem nice counterexamples. As so often, epistemology and ontology had become muddled.
| 8513 | Two red cloths are separate instances of redness, because you can dye one of them blue [Campbell,K] |
| 8514 | Red could only recur in a variety of objects if it was many, which makes them particulars [Campbell,K] |
| 8512 | Abstractions come before the mind by concentrating on a part of what is presented [Campbell,K] |
| 8515 | Tropes are basic particulars, so concrete particulars are collections of co-located tropes [Campbell,K] |
| 8518 | Events are trope-sequences, in which tropes replace one another [Campbell,K] |
| 8517 | Causal conditions are particular abstract instances of properties, which makes them tropes [Campbell,K] |
| 8516 | Davidson can't explain causation entirely by events, because conditions are also involved [Campbell,K] |
| 8519 | Bundles must be unique, so the Identity of Indiscernibles is a necessity - which it isn't! [Campbell,K] |
| 4033 | Two pure spheres in non-absolute space are identical but indiscernible [Campbell,K] |
| 8522 | Tropes solve the Companionship Difficulty, since the resemblance is only between abstract particulars [Campbell,K] |
| 8523 | Tropes solve the Imperfect Community problem, as they can only resemble in one respect [Campbell,K] |
| 8521 | Nominalism has the problem that without humans nothing would resemble anything else [Campbell,K] |
| 8524 | Trope theory makes space central to reality, as tropes must have a shape and size [Campbell,K] |
| 8525 | Relations need terms, so they must be second-order entities based on first-order tropes [Campbell,K] |