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It is not the case that The hyperreals and standard reals satisfy the transfer principle for first-order logical results, but behave differently for results about sets.
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Reasons For
2 perspectives
Reason for 1 of 2
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1.
The set of infinitesimal hyperreals lacks a least upper bound because 'least upper bound' in NSA refers to an internal set, not an external one.
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2.
The completeness axiom transfers correctly to hyperreals when restricted to internal sets, making the supporting argument's P3 a category error.
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3.
Robinson's transfer principle was explicitly formulated to apply only to internal properties, so citing external sets as counterexamples misrepresents the theorem's scope.
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Reason for 2 of 2
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1.
The claim conflates set-theoretic and model-theoretic senses of 'behave differently,' obscuring that hyperreals are elementarily equivalent to the reals.
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2.
Keisler and Robinson demonstrated that any first-order sentence true of the reals is true of the hyperreals, leaving no formal asymmetry at the level of truth.
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Reasons Against
1 perspective
Reason against
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1.
For results stated in a first-order logical language, the hyperreals and the standard reals satisfy the transfer principle.
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2.
Every bounded set of standard reals has a least upper bound.
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3.
The set of infinitesimal hyperreals is bounded but has no least upper bound.
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