essential properties

["John S. Denker" <jsd@MONMOUTH.COM>]

David Bowman wrote:
|" What is physical reality other than a collection of
| physical properties that happen to exist?"

Then Bob Sciamanda wrote:

> I think this goes to the heart of the matter.  Operationally, an electron
> is nothing more than the sum of its properties.  How else to define
> anything except in terms of its properties? - that is what it IS.  What is
> left to the concept "electron" after you have removed all of its
> properties?
>
> This, I think is in contrast to our (Aristotelian) intuition.
> Aristotelians (and the Scholastics) distinguished the "essence" of a thing
> from its properties ("substance" vs "accidents") - I don't think this is
> operationally valid, although it is intuitively natural.

I agree with about half of that.

Alas, things are not quite that simple.

By way of example, consider the discovery of the
"xtron" particle.

We first learn that xtrons are found whizzing around
inside atoms, carrying negative charge.

Is the negative charge an "essential" property?

Is being inside an atom an "essential" property?
You might think so, but then you'd have to beat
a hasty retreat when xtrons were found free,
outside of atoms.

Next we learn that xtrons move through wires,
carrying electric current.

Is being "the" current-carrier an "essential" property?
You might think so, but then you'd have to beat
a hasty retreat when current-carrying beams of
positive particles were discovered.

You get the idea:  You can't say that an object is
"nothing more than the sum of its properties" until
you know which properties are essential and which
are superficial and accidental.

You might think that things like mass and charge
are "essential" properties -- but even that's not
true in all contexts.  Carbon-12, carbon-13, and
carbon-14 have different masses, but they are all
"essentially" carbon atoms.

In summary:  Definitions are to some extent arbitrary.
The usual safe+easy thing to do is to use conventional
definitions.  This is where dictionaries come in:  a
good dictionary will tell you what properties are
conventionally considered essential.

If you want to use an unconventional definition, you
can, but then you have a heavy responsibility to make
your definitions explicit, and to verify that they are
consistent.  And... if you want anybody else to use
your definitions, you need motivate them and explain
why your definitions are better than the conventional
definitions.

This posting is the position of the writer, not that of Noah Webster or
Daniel Webster.

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.