(the following is a little wordy, but hopefully sets out why numbers might be human inventions, but the physical constants of quantity they describe and the numerical relationships between quantities are *not* human inventions… they are human *descriptions*.)
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a single object of a class of objects… this is the quantity we describe with the number 1
but the quantity described by the number 1 is not a human invention
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a single object, with another single object of the same class, together form a quantity we describe with the number 2
but the quantity described with the number 2 is not a human invention
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the quantity described by the number 2, is composed of a quantity described by the number 1 and another quantity described by the number 1
but the numerical relationship between the quantity described by the number 1 and the quantity described by the number 2, is not a human invention
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1+1=2 is simply a description of what is a natural law of the numerical relationship between the quantity described by the number 1 and the quantity described by the number 2