The claim that necessity holds in every possible world presupposes a fixed modal space, but the cardinality and structure of that space is itself a substantive metaphysical posit, not a logical truth.

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(Bolzano's formal definition, inapplicable to purely logical propositions)

A proposition is logically true if all of its i^s-variants (substitutions of extra-logical ideas) are true

modal(in logic and metaphysics)

Dealing with possibility and necessity—questions about what could be true, what must be true, and what's merely contingent (could go either way).

necessity(Auriol's modal theory of future contingents)

The property of necessarily being the way something is; equivalent to immutability in Auriol's modal theory

possible world(Leibniz's account of modality; 'existence' of possible worlds is shorthand for compossibility, not literal existence)

A set of compossible essences — a maximal collection of individual natures that can co-exist without contradiction

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