81 ideas
10073 | There cannot be a set theory which is complete [Smith,P] |
10616 | Second-order arithmetic can prove new sentences of first-order [Smith,P] |
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] |
10599 | For primes we write (x not= 1 ∧ ∀u∀v(u x v = x → (u = 1 ∨ v = 1))) [Smith,P] |
10610 | The reals contain the naturals, but the theory of reals doesn't contain the theory of naturals [Smith,P] |
10619 | The truths of arithmetic are just true equations and their universally quantified versions [Smith,P] |
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] |
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] |
10851 | Robinson Arithmetic 'Q' has basic axioms, quantifiers and first-order logic [Smith,P] |
10852 | Robinson Arithmetic (Q) is not negation complete [Smith,P] |
10068 | Natural numbers have zero, unique successors, unending, no circling back, and no strays [Smith,P] |
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] |
10617 | The 'ancestral' of a relation is a new relation which creates a long chain of the original relation [Smith,P] |
20043 | Evolutionary explanations look to the past or the group, not to the individual [Stout,R] |
20058 | Not all explanation is causal. We don't explain a painting's beauty, or the irrationality of root-2, that way [Stout,R] |
20035 | Philosophy of action studies the nature of agency, and of deliberate actions [Stout,R] |
20084 | Agency is causal processes that are sensitive to justification [Stout,R] |
20061 | Mental states and actions need to be separate, if one is to cause the other [Stout,R] |
20079 | Are actions bodily movements, or a sequence of intention-movement-result? [Stout,R] |
20080 | If one action leads to another, does it cause it, or is it part of it? [Stout,R] |
20059 | I do actions, but not events, so actions are not events [Stout,R] |
20081 | Bicycle riding is not just bodily movement - you also have to be on the bicycle [Stout,R] |
20039 | The causal theory says that actions are intentional when intention (or belief-desire) causes the act [Stout,R] |
20047 | Deciding what to do usually involves consulting the world, not our own minds [Stout,R] |
20065 | Should we study intentions in their own right, or only as part of intentional action? [Stout,R] |
20067 | You can have incompatible desires, but your intentions really ought to be consistent [Stout,R] |
20078 | The normativity of intentions would be obvious if they were internal promises [Stout,R] |
20044 | The rationalistic approach says actions are intentional when subject to justification [Stout,R] |
20036 | Intentional agency is seen in internal precursors of action, and in external reasons for the act [Stout,R] |
20066 | Speech needs sustained intentions, but not prior intentions [Stout,R] |
20073 | Bratman has to treat shared intentions as interrelated individual intentions [Stout,R] |
20069 | A request to pass the salt shares an intention that the request be passed on [Stout,R] |
20070 | An individual cannot express the intention that a group do something like moving a piano [Stout,R] |
20071 | An intention is a goal to which behaviour is adapted, for an individual or for a group [Stout,R] |
20038 | If the action of walking is just an act of will, then movement of the legs seems irrelevant [Stout,R] |
20050 | Most philosophers see causation as by an event or state in the agent, rather than the whole agent [Stout,R] |
20052 | If you don't mention an agent, you aren't talking about action [Stout,R] |
20077 | If you can judge one act as best, then do another, this supports an inward-looking view of agency [Stout,R] |
20049 | Maybe your emotions arise from you motivations, rather than being their cause [Stout,R] |
20046 | For an ascetic a powerful desire for something is a reason not to implement it [Stout,R] |
20060 | Beliefs, desires and intentions are not events, so can't figure in causal relations [Stout,R] |
20055 | A standard view says that the explanation of an action is showing its rational justification [Stout,R] |
20056 | In order to be causal, an agent's reasons must be internalised as psychological states [Stout,R] |
20053 | An action is only yours if you produce it, rather than some state or event within you [Stout,R] |
20048 | There may be a justification relative to a person's view, and yet no absolute justification [Stout,R] |
20068 | Describing a death as a side-effect rather than a goal may just be good public relations [Stout,R] |
20595 | You can't distribute goods from behind a veil, because their social meaning is unclear [Walzer, by Tuckness/Wolf] |
20592 | Complex equality restricts equalities from spilling over, like money influencing politics and law [Walzer, by Tuckness/Wolf] |
20549 | Equality is complex, with different spheres of equality where different principles apply [Walzer, by Swift] |
20083 | Aristotelian causation involves potentiality inputs into processes (rather than a pair of events) [Stout,R] |