- Extensions(what FO allegedly cannot express according to the claim)
- In logic, the set of all things that a property actually applies to—for example, the extension of 'red things' is everything that is red.
- Normative practices(as used in social philosophy)
- The shared rules, standards, or habits that a group of people follow about what is right, proper, or acceptable.
- Platonic structures(the alternative view being rejected—the idea that abstract structures exist on their own)
- Abstract, timeless perfect forms or ideals (from Plato's philosophy) that exist independently of the physical world and human minds.
- Wittgenstein
- Ludwig Wittgenstein was an Austrian-British philosopher who fundamentally changed how people think about language and meaning in the 20th century. He argued that many philosophical problems arise from misunderstanding how words actually work in everyday life, rather than from deep metaphysical mysteries. His ideas influenced not just philosophy but also mathematics, logic, and even how people approach psychology and artificial intelligence today.
- a priori(Frege treats 'analytic' as entailing 'a priori' for arithmetic.)
- Knowable independently of empirical experience; here treated as a consequence of analyticity.
- determinacy(Game theory, infinite games)
- The property that for any game property φ, either player i has a strategy to force a set of histories satisfying φ, or player j has a strategy to force ¬φ; formally: {i}φ ∨ {j}¬φ
- rule-following considerations(in philosophy of language)
- Wittgenstein's famous puzzle about how we know what rule to follow next: if you learn a rule by seeing examples, how do you know you're applying it correctly to new cases you've never seen before?