Lowenheim 1915 / Skolem 1920: countable theory has model of any infinite cardinality kappa; downward + upward versions; reveals first-order logic cannot pin down cardinality.
Lowenheim 1915 / Skolem 1920: countable theory has model of any infinite cardinality kappa; downward + upward versions; reveals first-order logic cannot pin down cardinality.