display all the ideas for this combination of philosophers
3 ideas
| 19043 | Bivalence applies not just to sentences, but that general terms are true or false of each object [Quine] |
| Full Idea: It is in the spirit of bivalence not just to treat each closed sentence as true or false; as Frege stressed, each general term must be definitely true or false of each object, specificiable or not. | |
| From: Willard Quine (What Price Bivalence? [1981], p.36) | |
| A reaction: But note that this is only the 'spirit' of the thing. If you had (as I do) doubts about whether predicates actually refer to genuine 'properties', you may want to stick to the whole sentence view, and not be so fine-grained. |
| 9024 | Excluded middle has three different definitions [Quine] |
| Full Idea: The law of excluded middle, or 'tertium non datur', may be pictured variously as 1) Every closed sentence is true or false; or 2) Every closed sentence or its negation is true; or 3) Every closed sentence is true or not true. | |
| From: Willard Quine (Philosophy of Logic [1970], Ch.6) | |
| A reaction: Unlike many top philosophers, Quine thinks clearly about such things. 1) is the classical bivalent reading of excluded middle; 2) is the purely syntactic version; 3) leaves open how we interpret the 'not-true' option. |
| 10012 | Quantification theory can still be proved complete if we add identity [Quine] |
| Full Idea: Complete proof procedures are available not only for quantification theory, but for quantification theory and identity together. Gödel showed that the theory is still complete if we add self-identity and the indiscernability of identicals. | |
| From: Willard Quine (Philosophy of Logic [1970], Ch.5) | |
| A reaction: Hence one talks of first-order logic 'with identity', even though, as Quine observes, it is unclear whether identity is actually a logical or a mathematical notion. |