95 ideas
11051 | Frege's logical approach dominates the analytical tradition [Hanna] |
11054 | Scientism says most knowledge comes from the exact sciences [Hanna] |
22289 | Dedekind proved definition by recursion, and thus proved the basic laws of arithmetic [Dedekind, by Potter] |
11070 | 'Denying the antecedent' fallacy: φ→ψ, ¬φ, so ¬ψ [Hanna] |
11071 | 'Affirming the consequent' fallacy: φ→ψ, ψ, so φ [Hanna] |
11088 | We can list at least fourteen informal fallacies [Hanna] |
11059 | Circular arguments are formally valid, though informally inadmissible [Hanna] |
11089 | Formally, composition and division fallacies occur in mereology [Hanna] |
10183 | An infinite set maps into its own proper subset [Dedekind, by Reck/Price] |
10073 | There cannot be a set theory which is complete [Smith,P] |
22288 | We have the idea of self, and an idea of that idea, and so on, so infinite ideas are available [Dedekind, by Potter] |
10706 | Dedekind originally thought more in terms of mereology than of sets [Dedekind, by Potter] |
11058 | Logic is explanatorily and ontologically dependent on rational animals [Hanna] |
11072 | Logic is personal and variable, but it has a universal core [Hanna] |
10616 | Second-order arithmetic can prove new sentences of first-order [Smith,P] |
11061 | Intensional consequence is based on the content of the concepts [Hanna] |
10076 | The 'range' of a function is the set of elements in the output set created by the function [Smith,P] |
10605 | Two functions are the same if they have the same extension [Smith,P] |
10075 | A 'partial function' maps only some elements to another set [Smith,P] |
10074 | A 'total function' maps every element to one element in another set [Smith,P] |
10612 | An argument is a 'fixed point' for a function if it is mapped back to itself [Smith,P] |
10615 | The Comprehension Schema says there is a property only had by things satisfying a condition [Smith,P] |
10595 | A 'theorem' of a theory is a sentence derived from the axioms using the proof system [Smith,P] |
10602 | A 'natural deduction system' has no axioms but many rules [Smith,P] |
10613 | No nice theory can define truth for its own language [Smith,P] |
10078 | An 'injective' ('one-to-one') function creates a distinct output element from each original [Smith,P] |
10077 | A 'surjective' ('onto') function creates every element of the output set [Smith,P] |
10079 | A 'bijective' function has one-to-one correspondence in both directions [Smith,P] |
10070 | If everything that a theory proves is true, then it is 'sound' [Smith,P] |
10086 | Soundness is true axioms and a truth-preserving proof system [Smith,P] |
10596 | A theory is 'sound' iff every theorem is true (usually from true axioms and truth-preservation) [Smith,P] |
10598 | A theory is 'negation complete' if it proves all sentences or their negation [Smith,P] |
10597 | 'Complete' applies both to whole logics, and to theories within them [Smith,P] |
10069 | A theory is 'negation complete' if one of its sentences or its negation can always be proved [Smith,P] |
10609 | Two routes to Incompleteness: semantics of sound/expressible, or syntax of consistency/proof [Smith,P] |
10080 | 'Effective' means simple, unintuitive, independent, controlled, dumb, and terminating [Smith,P] |
10087 | A theory is 'decidable' if all of its sentences could be mechanically proved [Smith,P] |
10088 | Any consistent, axiomatized, negation-complete formal theory is decidable [Smith,P] |
10081 | A set is 'enumerable' is all of its elements can result from a natural number function [Smith,P] |
10083 | A set is 'effectively enumerable' if a computer could eventually list every member [Smith,P] |
10084 | A finite set of finitely specifiable objects is always effectively enumerable (e.g. primes) [Smith,P] |
10085 | The set of ordered pairs of natural numbers <i,j> is effectively enumerable [Smith,P] |
10601 | The thorems of a nice arithmetic can be enumerated, but not the truths (so they're diffferent) [Smith,P] |
10600 | Being 'expressible' depends on language; being 'capture/represented' depends on axioms and proof system [Smith,P] |
9823 | Numbers are free creations of the human mind, to understand differences [Dedekind] |
10599 | For primes we write (x not= 1 ∧ ∀u∀v(u x v = x → (u = 1 ∨ v = 1))) [Smith,P] |
10090 | Dedekind defined the integers, rationals and reals in terms of just the natural numbers [Dedekind, by George/Velleman] |
17452 | Ordinals can define cardinals, as the smallest ordinal that maps the set [Dedekind, by Heck] |
7524 | Order, not quantity, is central to defining numbers [Dedekind, by Monk] |
14131 | Dedekind's ordinals are just members of any progression whatever [Dedekind, by Russell] |
10610 | The reals contain the naturals, but the theory of reals doesn't contain the theory of naturals [Smith,P] |
14437 | Dedekind's axiom that his Cut must be filled has the advantages of theft over honest toil [Dedekind, by Russell] |
18094 | Dedekind says each cut matches a real; logicists say the cuts are the reals [Dedekind, by Bostock] |
9824 | In counting we see the human ability to relate, correspond and represent [Dedekind] |
10619 | The truths of arithmetic are just true equations and their universally quantified versions [Smith,P] |
9826 | A system S is said to be infinite when it is similar to a proper part of itself [Dedekind] |
10608 | The number of Fs is the 'successor' of the Gs if there is a single F that isn't G [Smith,P] |
10618 | All numbers are related to zero by the ancestral of the successor relation [Smith,P] |
13508 | Dedekind gives a base number which isn't a successor, then adds successors and induction [Dedekind, by Hart,WD] |
10849 | Baby arithmetic covers addition and multiplication, but no general facts about numbers [Smith,P] |
10850 | Baby Arithmetic is complete, but not very expressive [Smith,P] |
10852 | Robinson Arithmetic (Q) is not negation complete [Smith,P] |
10851 | Robinson Arithmetic 'Q' has basic axioms, quantifiers and first-order logic [Smith,P] |
18096 | Zero is a member, and all successors; numbers are the intersection of sets satisfying this [Dedekind, by Bostock] |
10068 | Natural numbers have zero, unique successors, unending, no circling back, and no strays [Smith,P] |
18841 | Categoricity implies that Dedekind has characterised the numbers, because it has one domain [Rumfitt on Dedekind] |
14130 | Induction is proved in Dedekind, an axiom in Peano; the latter seems simpler and clearer [Dedekind, by Russell] |
10603 | The logic of arithmetic must quantify over properties of numbers to handle induction [Smith,P] |
10848 | Multiplication only generates incompleteness if combined with addition and successor [Smith,P] |
10604 | Incompleteness results in arithmetic from combining addition and successor with multiplication [Smith,P] |
8924 | Dedekind originated the structuralist conception of mathematics [Dedekind, by MacBride] |
9153 | Dedekindian abstraction talks of 'positions', where Cantorian abstraction talks of similar objects [Dedekind, by Fine,K] |
11063 | Logicism struggles because there is no decent theory of analyticity [Hanna] |
11055 | Supervenience can add covariation, upward dependence, and nomological connection [Hanna] |
10617 | The 'ancestral' of a relation is a new relation which creates a long chain of the original relation [Smith,P] |
9825 | A thing is completely determined by all that can be thought concerning it [Dedekind] |
11083 | A sentence is necessary if it is true in a set of worlds, and nonfalse in the other worlds [Hanna] |
11086 | Metaphysical necessity can be 'weak' (same as logical) and 'strong' (based on essences) [Hanna] |
11084 | Logical necessity is truth in all logically possible worlds, because of laws and concepts [Hanna] |
11085 | Nomological necessity is truth in all logically possible worlds with our laws [Hanna] |
11077 | Intuition includes apriority, clarity, modality, authority, fallibility and no inferences [Hanna] |
11080 | Intuition is more like memory, imagination or understanding, than like perception [Hanna] |
11078 | Intuition is only outside the 'space of reasons' if all reasons are inferential [Hanna] |
11053 | Explanatory reduction is stronger than ontological reduction [Hanna] |
11081 | Imagination grasps abstracta, generates images, and has its own correctness conditions [Hanna] |
11082 | Should we take the 'depictivist' or the 'descriptivist/propositionalist' view of mental imagery? [Hanna] |
11067 | Rational animals have a normative concept of necessity [Hanna] |
11068 | One tradition says talking is the essence of rationality; the other says the essence is logic [Hanna] |
11047 | Hegelian holistic rationality is the capacity to seek coherence [Hanna] |
11048 | Humean Instrumental rationality is the capacity to seek contingent truths [Hanna] |
11046 | Kantian principled rationality is recognition of a priori universal truths [Hanna] |
11045 | Most psychologists are now cognitivists [Hanna] |
9189 | Dedekind said numbers were abstracted from systems of objects, leaving only their position [Dedekind, by Dummett] |
9827 | We derive the natural numbers, by neglecting everything of a system except distinctness and order [Dedekind] |
9979 | Dedekind has a conception of abstraction which is not psychologistic [Dedekind, by Tait] |