39 ideas
18806 | Frege thought traditional categories had psychological and linguistic impurities [Frege, by Rumfitt] |
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] |
8490 | First-level functions have objects as arguments; second-level functions take functions as arguments [Frege] |
8492 | Relations are functions with two arguments [Frege] |
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] |
8487 | Arithmetic is a development of logic, so arithmetical symbolism must expand into logical symbolism [Frege] |
18899 | Frege takes the existence of horses to be part of their concept [Frege, by Sommers] |
4028 | Frege allows either too few properties (as extensions) or too many (as predicates) [Mellor/Oliver on Frege] |
8489 | The concept 'object' is too simple for analysis; unlike a function, it is an expression with no empty place [Frege] |
9947 | Concepts are the ontological counterparts of predicative expressions [Frege, by George/Velleman] |
10319 | An assertion about the concept 'horse' must indirectly speak of an object [Frege, by Hale] |
8488 | A concept is a function whose value is always a truth-value [Frege] |
9948 | Unlike objects, concepts are inherently incomplete [Frege, by George/Velleman] |
4972 | I may regard a thought about Phosphorus as true, and the same thought about Hesperus as false [Frege] |
21059 | General rules of action also need a judgement about when to apply them [Kant] |
21061 | Duty does not aim at an end, but gives rise to universal happiness as aim of the will [Kant] |
21060 | It can't be a duty to strive after the impossible [Kant] |
21062 | The will's motive is the absolute law itself, and moral feeling is receptivity to law [Kant] |
21071 | There can be no restraints on freedom if reason does not reveal some basic rights [Kant] |
21063 | Personal contracts are for some end, but a civil state contract involves a duty to share [Kant] |
21068 | There must be a unanimous contract that citizens accept majority decisions [Kant] |
21069 | A contract is theoretical, but it can guide rulers to make laws which the whole people will accept [Kant] |
21070 | A law is unjust if the whole people could not possibly agree to it [Kant] |
21067 | A citizen must control his own life, and possess property or an important skill [Kant] |
21064 | A lawful civil state must embody freedom, equality and independence for its members [Kant] |
21066 | Citizens can rise to any rank that talent, effort and luck can achieve [Kant] |
21065 | You can't make a contract renouncing your right to make contracts! [Kant] |
21072 | The people (who have to fight) and not the head of state should declare a war [Kant] |
8491 | The Ontological Argument fallaciously treats existence as a first-level concept [Frege] |