28 ideas
| 9821 | A definition need not capture the sense of an expression - just get the reference right [Frege, by Dummett] |
| 9585 | Since every definition is an equation, one cannot define equality itself [Frege] |
| 10147 | The Axiom of Choice is consistent with the other axioms of set theory [Feferman/Feferman] |
| 10148 | Axiom of Choice: a set exists which chooses just one element each of any set of sets [Feferman/Feferman] |
| 10149 | Platonist will accept the Axiom of Choice, but others want criteria of selection or definition [Feferman/Feferman] |
| 10150 | The Trichotomy Principle is equivalent to the Axiom of Choice [Feferman/Feferman] |
| 10146 | Cantor's theories needed the Axiom of Choice, but it has led to great controversy [Feferman/Feferman] |
| 10158 | A structure is a 'model' when the axioms are true. So which of the structures are models? [Feferman/Feferman] |
| 10162 | Tarski and Vaught established the equivalence relations between first-order structures [Feferman/Feferman] |
| 10160 | Löwenheim-Skolem says if the sentences are countable, so is the model [Feferman/Feferman] |
| 10159 | Löwenheim-Skolem Theorem, and Gödel's completeness of first-order logic, the earliest model theory [Feferman/Feferman] |
| 10161 | If a sentence holds in every model of a theory, then it is logically derivable from the theory [Feferman/Feferman] |
| 10156 | 'Recursion theory' concerns what can be solved by computing machines [Feferman/Feferman] |
| 10155 | Both Principia Mathematica and Peano Arithmetic are undecidable [Feferman/Feferman] |
| 17446 | Counting rests on one-one correspondence, of numerals to objects [Frege] |
| 9582 | Husserl rests sameness of number on one-one correlation, forgetting the correlation with numbers themselves [Frege] |
| 9586 | In a number-statement, something is predicated of a concept [Frege] |
| 9580 | Our concepts recognise existing relations, they don't change them [Frege] |
| 9589 | Numbers are not real like the sea, but (crucially) they are still objective [Frege] |
| 9577 | The naïve view of number is that it is like a heap of things, or maybe a property of a heap [Frege] |
| 9578 | If objects are just presentation, we get increasing abstraction by ignoring their properties [Frege] |
| 3643 | The concept of mind excludes body, and vice versa [Descartes] |
| 9581 | Many people have the same thought, which is the component, not the private presentation [Frege] |
| 9579 | Disregarding properties of two cats still leaves different objects, but what is now the difference? [Frege] |
| 9587 | How do you find the right level of inattention; you eliminate too many or too few characteristics [Frege] |
| 9588 | Number-abstraction somehow makes things identical without changing them! [Frege] |
| 9583 | Psychological logicians are concerned with sense of words, but mathematicians study the reference [Frege] |
| 9584 | Identity baffles psychologists, since A and B must be presented differently to identify them [Frege] |