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2 ideas
| 7927 | At different times Leibniz articulated three different versions of his so-called Law [Macdonald,C] |
| Full Idea: There are three distinct versions of Leibniz's Law, all traced to remarks made by Leibniz: the Identity of Indiscernibles (same properties, same thing), the Indiscernibility of Identicals (same thing, same properties), and the Substitution Principle. | |
| From: Cynthia Macdonald (Varieties of Things [2005], Ch.2) | |
| A reaction: The best view seems to be to treat the second one as Leibniz's Law (and uncontroversially true), and the first one as being an interesting but dubious claim. |
| 7928 | The Identity of Indiscernibles is false, because it is not necessarily true [Macdonald,C] |
| Full Idea: One common argument to the conclusion that the Principle of the Identity of Indiscernibles is false is that it is not necessarily true. | |
| From: Cynthia Macdonald (Varieties of Things [2005], Ch.2 n32) | |
| A reaction: This sounds like a good argument. If you test the Principle with an example ('this butler is the murderer') then total identity does not seem to necessitate identity, though it strongly implies it (the butler may have a twin etc). |