Is the concept of identicality of physical objects members ofthe same class aconvenient or necessary ideality?

Question

By "ideality", I specifically mean "scientific ideality"( I could not fit Q-box limits w/o the shortening)

nota bene:This is philosophy of physics or more generally a metaphysics Question.

note "identicality" is one of several "idealitities.

corrected note: "identicality" is one of several "idealities

Answer 1

Do you mean "identicality" or "ideality"?

Either way, I would answer, "strictly speaking, neither", but others would disagree.

Almost everyone (i.e. I don't know of any exceptions :-) would agree on the importance of equivalence - the idea that for the purposes at hand, any of a specified class would "equally" suitable or behave "essentially identically".

Similarly, almost everyone would agree about the importance of models, especially of behavior.

But for science, whether two instances, particularly of physical objects, are equivalent is a matter of the model and empirical observation (or, perhaps, assumption)

For scientist and philosophers, being human beings, the story is, of course, different.

At one extreme you have the followers of Plato who believe that everything is just a manifestation of an impossible ideal.
http://en.wikipedia.org/wiki/Platonic_ideal

In that context, any "identicality" would appear as an essential attribute, a reaffirmation of the underlying ideal.

At the other you have those who claim that there are no instances of true "identicality". There are just arbitrary categorizations, imposed by human beings to aid in their manipulation and attempts to describe reality.

(Years ago, the idea of two photons of the same frequency not being identical would have been a joke. Now, with even elementary particles capable of being linked at a distance, the idea isn't so funny. This is above and beyond the issue of whether two photons can actually have the "same" frequency.)

And there are even people that follow Pierre Teilhard de Chardin in believeing that everything, even atomic particles, have a "soul" or spiritual "dimension", which would surely make each one unique. (Chardin is interesting in this regard because he was a respected scientist, as well as being a trained theologian)

Answer 2

I think Simplicitus has given a great answer, even if I'm not so sure that he (or she) really answered your question.
I'm not sure because your question somehow got lost in the manifold asking of it.
Which brings us back to your original question...Which is... what?