Max Black's "The Identity of Indiscernibles"

[@TeacherOfPhilosophy]

Hey, all you nerds who are nerdy enough to care: For what is probably the first time ever, I introduce a _spaceship_ into the world of Castor and Pollux in a new piece of fiction! The ship is called the _Virgil_ for reasons I will not reveal at this time. You can look for the story "Or Whither Shall I Flee?" in this book when it comes out: kzbin.info/www/bejne/noezfaB5hNCArtU.

[@Platinho]

great video

[@NHHwng]

I was not expecting a cliffhanger!

[@TeacherOfPhilosophy]

Thanks for watching! I made this video more than a year ago, actually; I don't remember all that much about it (and I didn't stop to watch it again this morning). It looks like July 30, August 6, and August 13 will have more videos on this topic.

[@Spar__]

So PII is basically saying that positional property differentiates two objects/things even if they’re identical whereas indiscernibility of identity is x=y then x and y share every property in common thus they’re the same?

[@TeacherOfPhilosophy]

Not exactly on PII. PII would say that positional properties differentiate things even if all their _other_ properties are the same. And I think you got it on Indiscernibility of Identicals: If X = Y then they share every property.

[@Spar__]

TeacherOfPhilosophy what are their other properties in the hypothetical world? Given that they’re identically the same I couldn’t discern between the two spheres. Thus, would the only property be a positional property debunking PII?

[@TeacherOfPhilosophy]

You're asking for Max Black's position, right? The point is that they are _not_ distinguished by position or by other properties and _are_ indiscernible, and yet are _not_ identically the same.

[@TeacherOfPhilosophy]

By the way, I think I have three other videos on this topic, which might help to clarify things. In the Articles playlist you should find something about Carl Vaught, and something about John O'Leary-Hawthorne. And there should be one video on PII and Identity of Indiscernibles in the Topics playlist.

[@Spar__]

TeacherOfPhilosophy hmm...so the two spheres are two distinct things therefore they should be same by PII but what about the spheres makes them not identically the same if they’re both the same? Thank you! I believe I’ve check the part two of this, though I haven’t heard of those names you’ve mentioned and will do now.

[@mkraad]

Can we also say that PII also entails that if there exists at least ONE property of A that is not found in any property of B then A is not B? Would only one differing property suffice to have A and B not identical?

[@TeacherOfPhilosophy]

Technically, no. That's the Indiscernibility of Identicals, not PII--the Identity of Indiscernibles. But yes--one property will suffice.

[@williammilton7428]

very helpful thank you

[@Andre-pl2vg]

Do you know anything about "the identity of the indiscernibles" appearing in wittgenstein's tractatus?

[@TeacherOfPhilosophy]

No, to be honest. Been too long! But I can copy this for from my old notes on the _Tractatus_ : --a sign, such as a word, can be used in ordinary language to signify different things. --philosophy’s job is to clarify the boundaries of natural science by making it clearer what can be said. --most of the problems in philosophy are the result of using words in different ways. They aren’t even problems; they are not false but nonsensical. --in a clearer language, only one object would correspond to any given sign. --objects to the identity of indiscernibles because two different objects could have all the same properties. --identity is not an object in the world; it is only a rule governing the substitutivity of names in language. Hence in an artificial logical language there is no sign for identity; rather, two signs are simply identical.

[@Andre-pl2vg]

@@TeacherOfPhilosophy thanks for your notes, my job theses days has been to write about the proposition 2.0233.

[@mkraad]

PII is true bec If you draw an imaginery 3 dimentional system xyz the two spheres would not have the same coordinates unless they are one and the same sphere but they arent so sphere one is not sphere two

[@TeacherOfPhilosophy]

But in the case of Castor and Pollux, how do we distinguish one set of coordinates from the other?

[@mkraad]

@@TeacherOfPhilosophy through the imaginery coordinate system xyz...castor and polux would not have the same position on the axes no matter what axes we are measuring them on

[@TeacherOfPhilosophy]

I can almost hear the voice of B pointing out this coordinate system is only imaginary; in the world of Castor and Pollux, there _is_ no such system. If your point is that we can tell that Castor and Pollux are different, B agrees; that's actually _his_ point! But we're not telling them apart by any properties they actually have--only by their _imaginary_ properties. Does that count for PII?

[@TeacherOfPhilosophy]

But my own question is: If you do imagine a coordinate system xyz in their world, how do you know a point on the coordinate system from its mirror point?