Quantity has real concrete measurable effects that exist irrespective of the philosophical problem of classification. If I have two acorns I know I can potentially grow two very real trees. They are countable and that directly relates to the effect they can have on the world. I like to think that maybe every tree is one tree, or that all trees are part of a unity of "plants", but practically speaking seeds and trees are countable entities no matter how I classify them.
If there are two planets, we can discuss philosophically that one might be a "moon" and not a "planet", or in some sense that the planet is "continuous" with the space dust or whatever. But the existence of two distinct bodies in space will still create very specific gravitational fields from their interactions. Tides are different if you have one vs two moon, Lagrange points etc.
As for electromagnetic fields, I am not smart enough to make a judgement on that. They are described by complex numbers, but does that mean they reflect a physical embodiment of complex numbers? Or is it just that we require complex numbers in order to resolve their behavior into something measurable? I love to learn about electricity but sadly the math is beyond my ability.
> If I have two acorns I know I can potentially grow two very real trees.
There are 2-seeded acorns. And you can get more than 1 tree from 1 seed in some species by asexual reproduction. I guess it depends on how you count trees. All the possibilities I see (number of trunks, distinctive DNA, unconnected cliques of cells) are fuzzy and have unintuitive counterexamples.
If there are two planets, we can discuss philosophically that one might be a "moon" and not a "planet", or in some sense that the planet is "continuous" with the space dust or whatever. But the existence of two distinct bodies in space will still create very specific gravitational fields from their interactions. Tides are different if you have one vs two moon, Lagrange points etc.
As for electromagnetic fields, I am not smart enough to make a judgement on that. They are described by complex numbers, but does that mean they reflect a physical embodiment of complex numbers? Or is it just that we require complex numbers in order to resolve their behavior into something measurable? I love to learn about electricity but sadly the math is beyond my ability.