Re: More on identifiers

From: David BL <>
Date: Fri, 5 Jun 2009 04:14:00 -0700 (PDT)
Message-ID: <>

On Jun 5, 6:25 pm, "Walter Mitty" <> wrote:


> Consider two electrons. They both have the same mass, and they have the
> same charge. They might have opposite spins. But the minute we add a third
> electron, the spin of two of them is going to be identical. It seems that,
> on the surface at least, electrons do not have enough properties to carry
> identity. As you descend into lower level particles like quarks, things get
> even more this way. Particles seem more and more interchangeable.
> Subatomic particles might not have much to do with your objects in a box,
> but it seems to me that any theory of reality and identity that falls apart
> at the subatomic level should at least take that into account.

Two comments here:

Firstly I don't understand what this has to do with the example. It is not claimed that items will inevitably be distinguishable by their properties, only that it may happen to be a /requirement/ in the problem domain.

Secondly, (and this is very off topic) I think your understanding of QM isn't quite right. There is a requirement that the wave function exhibit exchange symmetry under exchange of two identical particles, meaning that it either remains the same or changes sign and it follows that no physical measurement can tell the difference. In addition, electrons are fermions and obey the exclusion principle which means no two electrons can share the same quantum state. So by exchange symmetry all electrons are the same, and by the exclusion principle all electrons are different. :-) Perhaps a better example for you would have been a condensate of boson particles, where an unlimited number of particles can occupy the same quantum state at the same time. Received on Fri Jun 05 2009 - 13:14:00 CEST

Original text of this message