37 ideas
13886 | Later Frege held that definitions must fix a function's value for every possible argument [Frege, by Wright,C] |
9845 | We can't define a word by defining an expression containing it, as the remaining parts are a problem [Frege] |
10019 | Only what is logically complex can be defined; what is simple must be pointed to [Frege] |
17926 | Rejecting double negation elimination undermines reductio proofs [Colyvan] |
17925 | Showing a disproof is impossible is not a proof, so don't eliminate double negation [Colyvan] |
11211 | If a sound conclusion comes from two errors that cancel out, the path of the argument must matter [Rumfitt] |
17924 | Excluded middle says P or not-P; bivalence says P is either true or false [Colyvan] |
11212 | The sense of a connective comes from primitively obvious rules of inference [Rumfitt] |
11210 | Standardly 'and' and 'but' are held to have the same sense by having the same truth table [Rumfitt] |
17929 | Löwenheim proved his result for a first-order sentence, and Skolem generalised it [Colyvan] |
17930 | Axioms are 'categorical' if all of their models are isomorphic [Colyvan] |
9886 | Cardinals say how many, and reals give measurements compared to a unit quantity [Frege] |
17928 | Ordinal numbers represent order relations [Colyvan] |
9889 | Real numbers are ratios of quantities [Frege, by Dummett] |
17923 | Intuitionists only accept a few safe infinities [Colyvan] |
17941 | Infinitesimals were sometimes zero, and sometimes close to zero [Colyvan] |
17922 | Reducing real numbers to rationals suggested arithmetic as the foundation of maths [Colyvan] |
17936 | Transfinite induction moves from all cases, up to the limit ordinal [Colyvan] |
10020 | Frege's biggest error is in not accounting for the senses of number terms [Hodes on Frege] |
10553 | A number is a class of classes of the same cardinality [Frege, by Dummett] |
17940 | Most mathematical proofs are using set theory, but without saying so [Colyvan] |
17931 | Structuralism say only 'up to isomorphism' matters because that is all there is to it [Colyvan] |
17932 | If 'in re' structures relies on the world, does the world contain rich enough structures? [Colyvan] |
9887 | Formalism misunderstands applications, metatheory, and infinity [Frege, by Dummett] |
8751 | Only applicability raises arithmetic from a game to a science [Frege] |
9891 | The first demand of logic is of a sharp boundary [Frege] |
17943 | Probability supports Bayesianism better as degrees of belief than as ratios of frequencies [Colyvan] |
17939 | Mathematics can reveal structural similarities in diverse systems [Colyvan] |
17938 | Mathematics can show why some surprising events have to occur [Colyvan] |
17934 | Proof by cases (by 'exhaustion') is said to be unexplanatory [Colyvan] |
17933 | Reductio proofs do not seem to be very explanatory [Colyvan] |
17935 | If inductive proofs hold because of the structure of natural numbers, they may explain theorems [Colyvan] |
17942 | Can a proof that no one understands (of the four-colour theorem) really be a proof? [Colyvan] |
17937 | Mathematical generalisation is by extending a system, or by abstracting away from it [Colyvan] |
9890 | The modern account of real numbers detaches a ratio from its geometrical origins [Frege] |
11846 | If we abstract the difference between two houses, they don't become the same house [Frege] |
11214 | We learn 'not' along with affirmation, by learning to either affirm or deny a sentence [Rumfitt] |