Consider this new puzzle in contrast to Leibniz's two identical spheres. In Leibniz's example, it is clear that there are indeed two spheres, but we cannot tell which is which. In this new example, what is at question is whether there are one or two Bruces; this is what is not decidable. And this despite there being a clear definite description of each: the Bruce on the left and the Bruce on the right.

In Leibniz example there are two spheres with one description.

In FIne's example there are two descriptions yet it is unclear if there are one or two individuals.

And this despite there being a clear definite description of each: the Bruce on the left and the Bruce on the right. — Banno

I admit to being philosophically illiterate, but if there were twins on the left and right, shouldn't there be four Bruces?

The scenario involves a person in a universe that is perfectly symmetrically arranged around her center of vision. — IEP

One Bruce is a kind of mirror image of the other. Not a simple reflection.

In FIne's example there are two descriptions yet it is unclear if there are one or two individuals. — Banno

I look at a graph on which are defined an x-axis and a y-axis. To the left of the y-axis is the line x=-1, to the right is the line x=1. There are two descriptions in this symmetric world, and two "individuals". But I see how one could say this is the same line in two places.

Stretching the idea a bit, in math a homeomorphism means a continuous transformation of one object into another (doughnut to coffee cup, e.g.) preserving certain attributes. If one Bruce undergoes this process into the other, they are in a sense the same - homeomorphic. In this case they don't even have to resemble each other.

I don't see any deep ideas here. It's simply another word game IMO.

I don't see any deep ideas here. It's simply another word game IMO. — jgill

The whole of philosophy in a knutshell.

The "deep" question is whether there are any individuals in the world, or if there are only properties, or is it some sort of combination? Frege held that names had both sense and reference, in order to account for the difference between, say, Hesperus (the evening star) and Phosphorus (the morning star).

Whereas most examples are of this sort, with a pair of names share an individual but not a description, here there are either two descriptions and two individuals, or two descriptions and on individual, and no way to decide which is the case.

A philosophical joke.

Does not this scenario presume one individual since it talks about duplicating the source? And if so, in principle, should be decidable.

I don't have access to the original argument, but the issue seems to me to be deciding between a universe that is indeed symmetrical and one that merely appears symmetrical. That is, she cannot tell if she is in a symmetrical universe with two Bruces or a universe with one Bruce viewed twice.

Yeah, I need to find that original. That said, maybe I can have a little fun here. Assuming she lives in a symmetrical universe, her everyday experience would be two Bruces.

It would be completely normal for her to see two Bruces, one on the left, and one on the right. Both moving in the same exact way, like every thing else her world. However, I could imagine her wondering. Wondering why two Bruces move the same way on both sides and two Johns move the same on both sides, but most times, the two Bruces move differently than the two Johns. Would she not wonder why this is the case? Would she not seek an expalnation. Then one day, she comes across a mirror, and see a a reflection of herself on one side, and another reflection on the other side. In this case, this reflection moves exactly as she does, on both sides. Would this experience give her insight into an explanation that all is not what it seems? From this imagination, maybe one day, she becomes a scientist, studies the brain, learns how the brain takes in light and forms visual images, and discovers that her brain(brains?) actually form two images. Would she not be able to determine the "underlying reality"?

Pick up a copy of Semantic Relations and the following is the pertinent excerpt of the "two Bruces":

"To this end, let us imagine a universe that is completely symmetric around someone's center of vision. Whatever she sees to her left is and looks qualitatively identical to something she sees on her right(not that she conceptualizes the two sides as "left" and "right" since that would introduce asymmetry) She is now introduced to two identical twins, one to her left and the other to her right, and she simultaneously names each of them "Bruce"; using a left token of "Bruce" for the left twin and a right token of "Bruce" for the right twin. The two tokens of "Bruce" are then always used in tandem so as not to disturb the symmetry. Thus if she uses the left token of "Bruce" to say "Bruce is wearing pink pajama," she simultaneously uses a right token of "Bruce" to utter the same thing. She can even assert the non-identity of the two Bruces by simultaneously uttering the one token of "Bruce" from the left side of her mouth, the other token from the right, and a word for non-identity from the middle of her month.

It seems intuitively clear that she has the use of two names or, at least, the ambiguous use of a single name; and this is something that the Fregean should in any case accept since the name or names can be used to state an informative identity. But what, then, is the difference in sense? By consideration of symmetry, there is no purely descriptive difference in the referents. And this in itself is enough to refute a view that takes sense to be a purely descriptive means of identifying a referent. We can even suppose that she is originally introduced to one person but, seeing him "double," takes him to be two people. Her use of the two names will then not even differ in their reference."

That is, she cannot tell if she is in a symmetrical universe with two Bruces or a universe with one Bruce viewed twice. — Banno

Hence, Leibniz's identity of indiscernibles rule. Gracias amigo for the profound insight.

Hence, Leibniz's identity of indiscernibles rule. — Agent Smith

Well, no. Rather if there are two identical Bruces, this is a counter instance. The issue is undecided.

Well, no. Rather if there are two identical Bruces, this is a counter instance. The issue is undecided. — Banno

:ok: Sorry, I was wrong.