### Single Idea 13842

#### [catalogued under 5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic]

Full Idea

Second-order logic has no chance of a completeness theorem unless one ventures into intensional entities and possible worlds.

Gist of Idea

Second-order completeness seems to need intensional entities and possible worlds

Source

Ian Hacking (What is Logic? [1979], §13)

Book Reference

'A Philosophical Companion to First-Order Logic', ed/tr. Hughes,R.I.G. [Hackett 1993], p.246