138 ideas
23657 | The existence of tensed verbs shows that not all truths are necessary truths [Reid] |
23655 | An ad hominem argument is good, if it is shown that the man's principles are inconsistent [Reid] |
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] |
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] |
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] |
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] |
10618 | All numbers are related to zero by the ancestral of the successor relation [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] |
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] |
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] |
23634 | Accepting the existence of anything presupposes the notion of existence [Reid] |
458 | Nothing could come out of nothing, and existence could never completely cease [Empedocles] |
5112 | Empedocles says things are at rest, unless love unites them, or hatred splits them [Empedocles, by Aristotle] |
10617 | The 'ancestral' of a relation is a new relation which creates a long chain of the original relation [Smith,P] |
23664 | Powers are quite distinct and simple, and so cannot be defined [Reid] |
23669 | Thinkers say that matter has intrinsic powers, but is also passive and acted upon [Reid] |
23666 | It is obvious that there could not be a power without a subject which possesses it [Reid] |
23651 | Universals are not objects of sense and cannot be imagined - but can be conceived [Reid] |
23650 | Only individuals exist [Reid] |
23649 | No one thinks two sheets possess a single whiteness, but all agree they are both white [Reid] |
13209 | There is no coming-to-be of anything, but only mixing and separating [Empedocles, by Aristotle] |
23647 | Objects have an essential constitution, producing its qualities, which we are too ignorant to define [Reid] |
1350 | Continuity is needed for existence, otherwise we would say a thing existed after it ceased to exist [Reid] |
457 | Substance is not created or destroyed in mortals, but there is only mixing and exchange [Empedocles] |
21322 | We treat slowly changing things as identical for the sake of economy in language [Reid] |
21320 | Identity is familiar to common sense, but very hard to define [Reid] |
1367 | Identity can only be affirmed of things which have a continued existence [Reid] |
11874 | Real identity admits of no degrees [Reid] |
11958 | Impossibilites are easily conceived in mathematics and geometry [Reid, by Molnar] |
23659 | If someone denies that he is thinking when he is conscious of it, we can only laugh [Reid] |
23662 | The existence of ideas is no more obvious than the existence of external objects [Reid] |
23661 | We are only aware of other beings through our senses; without that, we are alone in the universe [Reid] |
23635 | Truths are self-evident to sensible persons who understand them clearly without prejudice [Reid] |
7631 | Sensation is not committed to any external object, but perception is [Reid] |
23637 | Primary qualities are the object of mathematics [Reid] |
23638 | Secondary qualities conjure up, and are confused with, the sensations which produce them [Reid] |
23639 | It is unclear whether a toothache is in the mind or in the tooth, but the word has a single meaning [Reid] |
6492 | Reid is seen as the main direct realist of the eighteenth century [Reid, by Robinson,H] |
23633 | Many truths seem obvious, and point to universal agreement - which is what we find [Reid] |
23654 | In obscure matters the few must lead the many, but the many usually lead in common sense [Reid] |
23644 | Without memory we could have no concept of duration [Reid] |
23643 | We all trust our distinct memories (but not our distinct imaginings) [Reid] |
23660 | The theory of ideas, popular with philosophers, means past existence has to be proved [Reid] |
23641 | People dislike believing without evidence, and try to avoid it [Reid] |
23642 | If non-rational evidence reaches us, it is reason which then makes use of it [Reid] |
23549 | We treat testimony with a natural trade off of belief and caution [Reid, by Fricker,M] |
462 | One vision is produced by both eyes [Empedocles] |
1356 | A person is a unity, and doesn't come in degrees [Reid] |
23658 | Consciousness is an indefinable and unique operation [Reid] |
23665 | Consciousness is the power of mind to know itself, and minds are grounded in powers [Reid] |
1359 | Personal identity is the basis of all rights, obligations and responsibility [Reid] |
21319 | I can hardly care about rational consequence if it wasn't me conceiving the antecedent [Reid] |
21323 | The identity of a thief is only known by similarity, but memory gives certainty in our own case [Reid] |
21321 | Memory reveals my past identity - but so does testimony of other witnesses [Reid] |
21324 | If consciousness is transferable 20 persons can be 1; forgetting implies 1 can be 20 [Reid] |
21325 | Boy same as young man, young man same as old man, old man not boy, if forgotten! [Reid] |
21327 | If a stolen horse is identified by similitude, its identity is not therefore merely similitude [Reid] |
1366 | If consciousness is personal identity, it is continually changing [Reid] |
1352 | Thoughts change continually, but the self doesn't [Reid] |
23681 | The first motion or effect cannot be produced necessarily, so the First Cause must be a free agent [Reid] |
23676 | A willed action needs reasonable understanding of what is to be done [Reid] |
23668 | Our own nature attributes free determinations to our own will [Reid] |
23680 | We are morally free, because we experience it, we are accountable, and we pursue projects [Reid] |
22765 | Wisdom and thought are shared by all things [Empedocles] |
1524 | For Empedocles thinking is almost identical to perception [Empedocles, by Theophrastus] |
23652 | We must first conceive things before we can consider them [Reid] |
23656 | The structure of languages reveals a uniformity in basic human opinions [Reid] |
23630 | Only philosophers treat ideas as objects [Reid] |
23648 | First we notice and name attributes ('abstracting'); then we notice that subjects share them ('generalising') [Reid] |
23653 | If you can't distinguish the features of a complex object, your notion of it would be a muddle [Reid] |
23640 | Only mature minds can distinguish the qualities of a body [Reid] |
23629 | The ambiguity of words impedes the advancement of knowledge [Reid] |
23646 | Reference is by name, or a term-plus-circumstance, or ostensively, or by description [Reid] |
23645 | A word's meaning is the thing conceived, as fixed by linguistic experts [Reid] |
20051 | Reid said that agent causation is a unique type of causation [Reid, by Stout,R] |
23678 | A motive is merely an idea, like advice, and not a force for action [Reid] |
23663 | There are axioms of taste - such as a general consensus about a beautiful face [Reid] |
552 | Empedocles said good and evil were the basic principles [Empedocles, by Aristotle] |
23674 | If an attempted poisoning results in benefits, we still judge the agent a poisoner [Reid] |
23675 | We shouldn't do to others what would be a wrong to us in similar circumstances [Reid] |
23672 | To be virtuous, we must care about duty [Reid] |
23673 | Every worthy man has a principle of honour, and knows what is honourable [Reid] |
589 | 'Nature' is just a word invented by people [Empedocles] |
21823 | The principle of 'Friendship' in Empedocles is the One, and is bodiless [Empedocles, by Plotinus] |
2680 | Empedocles said that there are four material elements, and two further creative elements [Empedocles, by Aristotle] |
6002 | Empedocles says bone is water, fire and earth in ratio 2:4:2 [Empedocles, by Inwood] |
13207 | Fire, Water, Air and Earth are elements, being simple as well as homoeomerous [Empedocles, by Aristotle] |
459 | All change is unity through love or division through hate [Empedocles] |
13218 | The elements combine in coming-to-be, but how do the elements themselves come-to-be? [Aristotle on Empedocles] |
13225 | Love and Strife only explain movement if their effects are distinctive [Aristotle on Empedocles] |
460 | If the one Being ever diminishes it would no longer exist, and what could ever increase it? [Empedocles] |
23632 | Similar effects come from similar causes, and causes are only what are sufficient for the effects [Reid] |
8383 | Day and night are constantly conjoined, but they don't cause one another [Reid, by Crane] |
23677 | We all know that mere priority or constant conjunction do not have to imply causation [Reid] |
23667 | Regular events don't imply a cause, without an innate conviction of universal causation [Reid] |
23679 | The principle of the law of nature is that matter is passive, and is acted upon [Reid] |
23670 | Scientists don't know the cause of magnetism, and only discover its regulations [Reid] |
23671 | Laws are rules for effects, but these need a cause; rules of navigation don't navigate [Reid] |
5090 | Maybe bodies are designed by accident, and the creatures that don't work are destroyed [Empedocles, by Aristotle] |
466 | God is pure mind permeating the universe [Empedocles] |
461 | God is a pure, solitary, and eternal sphere [Empedocles] |
1719 | In Empedocles' theory God is ignorant because, unlike humans, he doesn't know one of the elements (strife) [Aristotle on Empedocles] |
1522 | It is wretched not to want to think clearly about the gods [Empedocles] |