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Do we draw a distinction between a number as an element of the reals, and an element of the naturals?
I see in some explanations of attempts to formalize numbers such as Von Neumann's ordinals like in this rather philosophical question that we can draw a distinction between a real number '1' and a ...
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Definable real numbers
Reading this Wikipedia page I found this definition:
A real number $a$ is first-order definable in the language of set
theory, without parameters, if there is a formula $\phi$ in the
language ...
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