Dear Peter
I agree with the following your views:
Only '"A is not B" is true.
Studying physical entities afresh it becomes apparent.. that for sizes at observable scalesno two physical entities are identical. ..no two galaxies, planets, trees, people, snowflakes or grains of sand will be found absolutely identical ...at a molecular level.
Now we must think more broadly and ask "Is anything in the universe precisely identical?! Clearly no Cluster, Galaxy, Solar System, Planet, Creature, Snowflake, or particle of anything physical we can observe with our best instruments are absolutely identical!
But should that discourage us from seeking the truth. If you look at Boskovic's force curves that forces are there and therefore energy and masses are scattered between two points, ie they are never above one point, which would result in identical masses. But there are cases in nature where these two points are so close that we can speak of equality, that is, of the constancy of some physical parameter. Thus, for example, two protons by mass differ somewhere at 10 ^ N decimals, where N is a large number. But there are parameters such as Planck values that are limits or mean values but do not exist in nature anywhere. Not even a single photon travels at the same speed as light, but the difference is immeasurably small. There are articles on this. Previously, it did not discourage me, but rather led me to find another such important parameter that I called the fundamental particle. Of course, such a particle does not exist, but all other particles are in relation to it. We cannot say: proton A is identical to proton B, but we can say Planck's mass is identical anywhere in the universe. The same goes for the fundamental particle. In my essay, some predictive formulas obtained using a fundamental particle are shown in relation to Planck's values.
Regards Branko