164 ideas
13466 | We are all post-Kantians, because he set the current agenda for philosophy [Hart,WD] |
19250 | Everything interesting should be recorded, with records that can be rearranged [Peirce] |
19228 | Sciences concern existence, but philosophy also concerns potential existence [Peirce] |
13477 | The problems are the monuments of philosophy [Hart,WD] |
19241 | An idea on its own isn't an idea, because they are continuous systems [Peirce] |
19227 | Philosophy is a search for real truth [Peirce] |
19218 | Metaphysics is pointless without exact modern logic [Peirce] |
21489 | Super-ordinate disciplines give laws or principles; subordinate disciplines give concrete cases [Peirce, by Atkin] |
6947 | Metaphysics does not rest on facts, but on what we are inclined to believe [Peirce] |
14799 | Metaphysics rests on observations, but ones so common we hardly notice them [Peirce] |
19229 | Metaphysics is the science of both experience, and its general laws and types [Peirce] |
19219 | Metaphysical reasoning is simple enough, but the concepts are very hard [Peirce] |
14767 | The demonstrations of the metaphysicians are all moonshine [Peirce] |
19231 | Metaphysics is turning into logic, and logic is becoming mathematics [Peirce] |
13515 | To study abstract problems, some knowledge of set theory is essential [Hart,WD] |
14764 | I am saturated with the spirit of physical science [Peirce] |
14782 | Philosophy is an experimental science, resting on common experience [Peirce] |
6937 | Reason aims to discover the unknown by thinking about the known [Peirce] |
14779 | I reason in order to avoid disappointment and surprise [Peirce] |
14787 | Self-contradiction doesn't reveal impossibility; it is inductive impossibility which reveals self-contradiction [Peirce] |
19247 | The one unpardonable offence in reasoning is to block the route to further truth [Peirce] |
13469 | Tarski showed how we could have a correspondence theory of truth, without using 'facts' [Hart,WD] |
7661 | Truth is the opinion fated to be ultimately agreed by all investigators [Peirce] |
19095 | Pragmatic 'truth' is a term to cover the many varied aims of enquiry [Peirce, by Misak] |
19097 | Peirce did not think a belief was true if it was useful [Peirce, by Misak] |
21494 | If truth is the end of enquiry, what if it never ends, or ends prematurely? [Atkin on Peirce] |
14796 | Independent truth (if there is any) is the ultimate result of sufficient enquiry [Peirce] |
19246 | 'Holding for true' is either practical commitment, or provisional theory [Peirce] |
15335 | Peirce's theory offers anti-realist verificationism, but surely how things are is independent of us? [Horsten on Peirce] |
13504 | Truth for sentences is satisfaction of formulae; for sentences, either all sequences satisfy it (true) or none do [Hart,WD] |
13503 | A first-order language has an infinity of T-sentences, which cannot add up to a definition of truth [Hart,WD] |
14777 | That a judgement is true and that we judge it true are quite different things [Peirce] |
13500 | Conditional Proof: infer a conditional, if the consequent can be deduced from the antecedent [Hart,WD] |
13502 | ∃y... is read as 'There exists an individual, call it y, such that...', and not 'There exists a y such that...' [Hart,WD] |
13456 | Set theory articulates the concept of order (through relations) [Hart,WD] |
13497 | Nowadays ZFC and NBG are the set theories; types are dead, and NF is only useful for the whole universe [Hart,WD] |
13443 | ∈ relates across layers, while ⊆ relates within layers [Hart,WD] |
13442 | Without the empty set we could not form a∩b without checking that a and b meet [Hart,WD] |
13493 | In the modern view, foundation is the heart of the way to do set theory [Hart,WD] |
13495 | Foundation Axiom: an nonempty set has a member disjoint from it [Hart,WD] |
13461 | We can choose from finite and evident sets, but not from infinite opaque ones [Hart,WD] |
13462 | With the Axiom of Choice every set can be well-ordered [Hart,WD] |
13516 | If we accept that V=L, it seems to settle all the open questions of set theory [Hart,WD] |
13441 | Naïve set theory has trouble with comprehension, the claim that every predicate has an extension [Hart,WD] |
13494 | The iterative conception may not be necessary, and may have fixed points or infinitely descending chains [Hart,WD] |
13457 | A 'partial ordering' is irreflexive and transitive; the sets are ordered, but not the subsets [Hart,WD] |
13458 | A partial ordering becomes 'total' if any two members of its field are comparable [Hart,WD] |
13490 | Von Neumann defines α<β as α∈β [Hart,WD] |
13460 | 'Well-ordering' must have a least member, so it does the natural numbers but not the integers [Hart,WD] |
13481 | Maybe sets should be rethought in terms of the even more basic categories [Hart,WD] |
14780 | Only study logic if you think your own reasoning is deficient [Peirce] |
19237 | Deduction is true when the premises facts necessarily make the conclusion fact true [Peirce] |
19256 | Our research always hopes that reality embodies the logic we are employing [Peirce] |
14783 | Logic, unlike mathematics, is not hypothetical; it asserts categorical ends from hypothetical means [Peirce] |
21493 | Pure mathematics deals only with hypotheses, of which the reality does not matter [Peirce] |
19102 | Bivalence is a regulative assumption of enquiry - not a law of logic [Peirce, by Misak] |
19238 | The logic of relatives relies on objects built of any relations (rather than on classes) [Peirce] |
13506 | The universal quantifier can't really mean 'all', because there is no universal set [Hart,WD] |
13513 | Models are ways the world might be from a first-order point of view [Hart,WD] |
13505 | Model theory studies how set theory can model sets of sentences [Hart,WD] |
13511 | Model theory is mostly confined to first-order theories [Hart,WD] |
13512 | Modern model theory begins with the proof of Los's Conjecture in 1962 [Hart,WD] |
13496 | First-order logic is 'compact': consequences of a set are consequences of a finite subset [Hart,WD] |
13484 | Berry's Paradox: we succeed in referring to a number, with a term which says we can't do that [Hart,WD] |
13482 | The Burali-Forti paradox is a crisis for Cantor's ordinals [Hart,WD] |
13507 | The machinery used to solve the Liar can be rejigged to produce a new Liar [Hart,WD] |
9117 | The smallest heap has four objects: three on the bottom, one on the top [Hart,WD, by Sorensen] |
13459 | The less-than relation < well-orders, and partially orders, and totally orders the ordinal numbers [Hart,WD] |
13463 | There are at least as many infinite cardinals as transfinite ordinals (because they will map) [Hart,WD] |
13491 | The axiom of infinity with separation gives a least limit ordinal ω [Hart,WD] |
13492 | Von Neumann's ordinals generalise into the transfinite better, because Zermelo's ω is a singleton [Hart,WD] |
13446 | 19th century arithmetization of analysis isolated the real numbers from geometry [Hart,WD] |
14775 | Numbers are just names devised for counting [Peirce] |
13509 | We can establish truths about infinite numbers by means of induction [Hart,WD] |
13474 | Euclid has a unique parallel, spherical geometry has none, and saddle geometry has several [Hart,WD] |
14776 | That two two-eyed people must have four eyes is a statement about numbers, not a fact [Peirce] |
14788 | Mathematics is close to logic, but is even more abstract [Peirce] |
13471 | Mathematics makes existence claims, but philosophers usually say those are never analytic [Hart,WD] |
19226 | We now know that mathematics only studies hypotheses, not facts [Peirce] |
13488 | Mass words do not have plurals, or numerical adjectives, or use 'fewer' [Hart,WD] |
21492 | Realism is basic to the scientific method [Peirce] |
19240 | Realism is the belief that there is something in the being of things corresponding to our reasoning [Peirce] |
19239 | There may be no reality; it's just our one desperate hope of knowing anything [Peirce] |
10352 | The real is the idea in which the community ultimately settles down [Peirce] |
6949 | If someone doubted reality, they would not actually feel dissatisfaction [Peirce] |
14778 | Facts are hard unmoved things, unaffected by what people may think of them [Peirce] |
13498 | Peirce and others began the mapping out of relations [Peirce, by Hart,WD] |
21491 | Peirce's later realism about possibilities and generalities went beyond logical positivism [Peirce, by Atkin] |
14798 | All communication is vague, and is outside the principle of non-contradiction [Peirce] |
14797 | Vagueness is a neglected but important part of mathematical thought [Peirce] |
14786 | Some logical possibility concerns single propositions, but there is also compatibility between propositions [Peirce] |
19252 | Objective chance is the property of a distribution [Peirce] |
14804 | Is chance just unknown laws? But the laws operate the same, whatever chance occurs [Peirce] |
14303 | Truth-functional conditionals have a simple falsification, when A is true and B is false [Peirce] |
19232 | In ordinary language a conditional statement assumes that the antecedent is true [Peirce] |
16376 | The possible can only be general, and the force of actuality is needed to produce a particular [Peirce] |
19089 | Our whole conception of an object is its possible practical consequences [Peirce] |
7660 | We are aware of beliefs, they appease our doubts, and they are rules of action, or habits [Peirce] |
6940 | The feeling of belief shows a habit which will determine our actions [Peirce] |
6943 | A mere question does not stimulate a struggle for belief; there must be a real doubt [Peirce] |
6941 | We are entirely satisfied with a firm belief, even if it is false [Peirce] |
6942 | We want true beliefs, but obviously we think our beliefs are true [Peirce] |
19223 | We act on 'full belief' in a crisis, but 'opinion' only operates for trivial actions [Peirce] |
14781 | A 'belief' is a habit which determines how our imagination and actions proceed [Peirce] |
19107 | Inquiry is not standing on bedrock facts, but standing in hope on a shifting bog [Peirce] |
14770 | Reasoning is based on statistical induction, so it can't achieve certainty or precision [Peirce] |
14768 | Infallibility in science is just a joke [Peirce] |
13480 | Fregean self-evidence is an intrinsic property of basic truths, rules and definitions [Hart,WD] |
14774 | Innate truths are very uncertain and full of error, so they certainly have exceptions [Peirce] |
13476 | The failure of key assumptions in geometry, mereology and set theory throw doubt on the a priori [Hart,WD] |
14789 | Experience is indeed our only source of knowledge, provided we include inner experience [Peirce] |
19253 | We talk of 'association by resemblance' but that is wrong: the association constitutes the resemblance [Peirce] |
14765 | Association of ideas is the best philosophical idea of the prescientific age [Peirce] |
14794 | Instead of seeking Truth, we should seek belief that is beyond doubt [Peirce] |
14795 | Pragmatism is a way of establishing meanings, not a theory of metaphysics or a set of truths [Peirce] |
14785 | The world is one of experience, but experiences are always located among our ideas [Peirce] |
14772 | If we decide an idea is inspired, we still can't be sure we have got the idea right [Peirce] |
14773 | A truth is hard for us to understand if it rests on nothing but inspiration [Peirce] |
14771 | Only reason can establish whether some deliverance of revelation really is inspired [Peirce] |
6598 | We need our beliefs to be determined by some external inhuman permanency [Peirce] |
19224 | Scientists will give up any conclusion, if experience opposes it [Peirce] |
6944 | Demonstration does not rest on first principles of reason or sensation, but on freedom from actual doubt [Peirce] |
6948 | Doubts should be satisfied by some external permanency upon which thinking has no effect [Peirce] |
6945 | Once doubt ceases, there is no point in continuing to argue [Peirce] |
19243 | If each inference slightly reduced our certainty, science would soon be in trouble [Peirce] |
19225 | I classify science by level of abstraction; principles derive from above, and data from below [Peirce] |
14766 | Duns Scotus offers perhaps the best logic and metaphysics for modern physical science [Peirce] |
19234 | 'Induction' doesn't capture Greek 'epagoge', which is singulars in a mass producing the general [Peirce] |
19236 | Induction can never prove that laws have no exceptions [Peirce] |
19251 | The worst fallacy in induction is generalising one recondite property from a sample [Peirce] |
19235 | How does induction get started? [Peirce] |
14790 | 'Abduction' is beginning a hypothesis, particularly if it includes preference of one explanation over others [Peirce] |
14791 | Abduction involves original suggestions, and not just the testing involved in induction [Peirce] |
19222 | Men often answer inner 'whys' by treating unconscious instincts as if they were reasons [Peirce] |
19220 | We may think animals reason very little, but they hardly ever make mistakes! [Peirce] |
14769 | Only imagination can connect phenomena together in a rational way [Peirce] |
19255 | Generalisation is the great law of mind [Peirce] |
19242 | Generalization is the true end of life [Peirce] |
19249 | 'Know yourself' is not introspection; it is grasping how others see you [Peirce] |
14802 | Physical and psychical laws of mind are either independent, or derived in one or other direction [Peirce] |
19257 | Whatever is First must be sentient [Peirce] |
19248 | Reasoning involves observation, experiment, and habituation [Peirce] |
19221 | Everybody overrates their own reasoning, so it is clearly superficial [Peirce] |
14792 | A 'conception', the rational implication of a word, lies in its bearing upon the conduct of life [Peirce] |
13475 | The Fregean concept of GREEN is a function assigning true to green things, and false to the rest [Hart,WD] |
14793 | The definition of a concept is just its experimental implications [Peirce] |
19087 | The meaning or purport of a symbol is all the rational conduct it would lead to [Peirce] |
14906 | Non-positivist verificationism says only take a hypothesis seriously if it is scientifically based and testable [Ladyman/Ross on Peirce] |
7634 | Icons resemble their subject, an index is a natural sign, and symbols are conventional [Peirce, by Maund] |
19233 | Indexicals are unusual words, because they stimulate the hearer to look around [Peirce] |
14784 | Ethics is the science of aims [Peirce] |
14805 | Is there any such thing as death among the lower organisms? [Peirce] |
19230 | People should follow what lies before them, and is within their power [Peirce] |
19245 | We are not inspired by other people's knowledge; a sense of our ignorance motivates study [Peirce] |
19244 | Chemists rely on a single experiment to establish a fact; repetition is pointless [Peirce] |
6939 | What is true of one piece of copper is true of another (unlike brass) [Peirce] |
14800 | The world is full of variety, but laws seem to produce uniformity [Peirce] |
19254 | Our laws of nature may be the result of evolution [Peirce] |
14806 | If the world is just mechanical, its whole specification has no more explanation than mere chance [Peirce] |
14803 | The more precise the observations, the less reliable appear to be the laws of nature [Peirce] |
6938 | Natural selection might well fill an animal's mind with pleasing thoughts rather than true ones [Peirce] |
14801 | Darwinian evolution is chance, with the destruction of bad results [Peirce] |
6946 | If death is annihilation, belief in heaven is a cheap pleasure with no disappointment [Peirce] |
1513 | The Egyptians were the first to say the soul is immortal and reincarnated [Herodotus] |