94 ideas
| 23966 | The personal view can still be objective, so I call sciences 'impersonal', rather than objective [Goldie] |
| 22271 | Aristotle was the first to use schematic letters in logic [Aristotle, by Potter] |
| 11060 | Aristotelian syllogisms are three-part, subject-predicate, existentially committed, with laws of thought [Aristotle, by Hanna] |
| 18909 | Aristotelian sentences are made up by one of four 'formative' connectors [Aristotle, by Engelbretsen] |
| 8080 | Aristotelian identified 256 possible syllogisms, saying that 19 are valid [Aristotle, by Devlin] |
| 13912 | Aristotle replaced Plato's noun-verb form with unions of pairs of terms by one of four 'copulae' [Aristotle, by Engelbretsen/Sayward] |
| 8071 | Aristotle listed nineteen valid syllogisms (though a few of them were wrong) [Aristotle, by Devlin] |
| 13819 | Aristotle's said some Fs are G or some Fs are not G, forgetting that there might be no Fs [Bostock on Aristotle] |
| 13689 | 'Theorems' are formulas provable from no premises at all [Sider] |
| 13705 | Truth tables assume truth functionality, and are just pictures of truth functions [Sider] |
| 13706 | Intuitively, deontic accessibility seems not to be reflexive, but to be serial [Sider] |
| 13710 | In D we add that 'what is necessary is possible'; then tautologies are possible, and contradictions not necessary [Sider] |
| 13711 | System B introduces iterated modalities [Sider] |
| 13708 | S5 is the strongest system, since it has the most valid formulas, because it is easy to be S5-valid [Sider] |
| 9403 | There are three different deductions for actual terms, necessary terms and possible terms [Aristotle] |
| 13712 | Epistemic accessibility is reflexive, and allows positive and negative introspection (KK and K¬K) [Sider] |
| 13714 | We can treat modal worlds as different times [Sider] |
| 13720 | Converse Barcan Formula: □∀αφ→∀α□φ [Sider] |
| 13718 | The Barcan Formula ∀x□Fx→□∀xFx may be a defect in modal logic [Sider] |
| 13723 | System B is needed to prove the Barcan Formula [Sider] |
| 13715 | You can employ intuitionist logic without intuitionism about mathematics [Sider] |
| 13678 | The most popular account of logical consequence is the semantic or model-theoretic one [Sider] |
| 13679 | Maybe logical consequence is more a matter of provability than of truth-preservation [Sider] |
| 13682 | Maybe logical consequence is impossibility of the premises being true and the consequent false [Sider] |
| 13680 | Maybe logical consequence is a primitive notion [Sider] |
| 11148 | Deduction is when we suppose one thing, and another necessarily follows [Aristotle] |
| 13722 | A 'theorem' is an axiom, or the last line of a legitimate proof [Sider] |
| 18896 | Aristotle places terms at opposite ends, joined by a quantified copula [Aristotle, by Sommers] |
| 13696 | When a variable is 'free' of the quantifier, the result seems incapable of truth or falsity [Sider] |
| 13700 | A 'total' function must always produce an output for a given domain [Sider] |
| 3300 | Aristotle's logic is based on the subject/predicate distinction, which leads him to substances and properties [Aristotle, by Benardete,JA] |
| 13703 | λ can treat 'is cold and hungry' as a single predicate [Sider] |
| 11149 | Affirming/denying sentences are universal, particular, or indeterminate [Aristotle] |
| 8079 | Aristotelian logic has two quantifiers of the subject ('all' and 'some') [Aristotle, by Devlin] |
| 13688 | Good axioms should be indisputable logical truths [Sider] |
| 13687 | No assumptions in axiomatic proofs, so no conditional proof or reductio [Sider] |
| 13690 | Proof by induction 'on the length of the formula' deconstructs a formula into its accepted atoms [Sider] |
| 13691 | Induction has a 'base case', then an 'inductive hypothesis', and then the 'inductive step' [Sider] |
| 13685 | Natural deduction helpfully allows reasoning with assumptions [Sider] |
| 13686 | We can build proofs just from conclusions, rather than from plain formulae [Sider] |
| 13697 | Valuations in PC assign truth values to formulas relative to variable assignments [Sider] |
| 13684 | The semantical notion of a logical truth is validity, being true in all interpretations [Sider] |
| 13704 | It is hard to say which are the logical truths in modal logic, especially for iterated modal operators [Sider] |
| 13724 | In model theory, first define truth, then validity as truth in all models, and consequence as truth-preservation [Sider] |
| 13698 | In a complete logic you can avoid axiomatic proofs, by using models to show consequences [Sider] |
| 13699 | Compactness surprisingly says that no contradictions can emerge when the set goes infinite [Sider] |
| 13701 | A single second-order sentence validates all of arithmetic - but this can't be proved axiomatically [Sider] |
| 13692 | A 'precisification' of a trivalent interpretation reduces it to a bivalent interpretation [Sider] |
| 13695 | Supervaluational logic is classical, except when it adds the 'Definitely' operator [Sider] |
| 13693 | A 'supervaluation' assigns further Ts and Fs, if they have been assigned in every precisification [Sider] |
| 13694 | We can 'sharpen' vague terms, and then define truth as true-on-all-sharpenings [Sider] |
| 13683 | A relation is a feature of multiple objects taken together [Sider] |
| 13702 | The identity of indiscernibles is necessarily true, if being a member of some set counts as a property [Sider] |
| 13721 | 'Strong' necessity in all possible worlds; 'weak' necessity in the worlds where the relevant objects exist [Sider] |
| 14641 | A deduction is necessary if the major (but not the minor) premise is also necessary [Aristotle] |
| 13707 | Maybe metaphysical accessibility is intransitive, if a world in which I am a frog is impossible [Sider] |
| 13709 | Logical truths must be necessary if anything is [Sider] |
| 13716 | 'If B hadn't shot L someone else would have' if false; 'If B didn't shoot L, someone else did' is true [Sider] |
| 13717 | Transworld identity is not a problem in de dicto sentences, which needn't identify an individual [Sider] |
| 13719 | Barcan Formula problem: there might have been a ghost, despite nothing existing which could be a ghost [Sider] |
| 24005 | We know other's emotions by explanation, contagion, empathy, imagination, or sympathy [Goldie] |
| 24006 | Empathy and imagining don't ensure sympathy, and sympathy doesn't need them [Goldie] |
| 18911 | Linguistic terms form a hierarchy, with higher terms predicable of increasing numbers of things [Aristotle, by Engelbretsen] |
| 23978 | 'Having an emotion' differs from 'being emotional' [Goldie] |
| 23973 | Unlike moods, emotions have specific objects, though the difference is a matter of degree [Goldie] |
| 23974 | Emotional intentionality as belief and desire misses out the necessity of feelings [Goldie] |
| 23972 | A long lasting and evolving emotion is still seen as a single emotion, such as love [Goldie] |
| 23992 | Some Aborigines have fifteen different words for types of fear [Goldie] |
| 23979 | Emotional responses can reveal to us our values, which might otherwise remain hidden [Goldie] |
| 23976 | If we have a 'feeling towards' an object, that gives the recognition a different content [Goldie] |
| 23977 | When actions are performed 'out of' emotion, they appear to be quite different [Goldie] |
| 23980 | It is best to see emotions holistically, as embedded in a person's life narrative [Goldie] |
| 23982 | If emotions are 'towards' things, they can't be bodily feelings, which lack aboutness [Goldie] |
| 24001 | Moods can focus as emotions, and emotions can blur into moods [Goldie] |
| 23968 | If reasons are seen impersonally (as just causal), then feelings are an irrelevant extra [Goldie] |
| 23969 | We have feelings of which we are hardly aware towards things in the world [Goldie] |
| 23984 | An emotion needs episodes of feeling, but not continuously [Goldie] |
| 23970 | Emotions are not avocado pears, with a rigid core and changeable surface [Goldie] |
| 23985 | A basic emotion is the foundation of a hierarchy, such as anger for types of annoyance [Goldie] |
| 23986 | Early Chinese basic emotions: joy, anger, sadness, fear, love, disliking, and liking [Goldie] |
| 23991 | Cross-cultural studies of facial expressions suggests seven basic emotions [Goldie] |
| 23967 | Some emotions are direct responses, and neither rational nor irrational [Goldie] |
| 23971 | Emotional thought is not rational, but it can be intelligible [Goldie] |
| 23975 | Learning an evaluative property like 'dangerous' is also learning an emotion [Goldie] |
| 23983 | We call emotions 'passions' because they are not as controlled as we would like [Goldie] |
| 23999 | Emotional control is hard, but we are responsible for our emotions over long time periods [Goldie] |
| 23994 | Emotions are not easily changed, as new knowledge makes little difference, and akrasia is possible [Goldie] |
| 23998 | Emotional control is less concerned with emotional incidents, and more with emotional tendencies [Goldie] |
| 23995 | Akrasia can be either overruling our deliberation, or failing to deliberate [Goldie] |
| 24000 | Justifying reasons say you were right; excusing reasons say your act was explicable [Goldie] |
| 24003 | Character traits are both possession of and lack of dispositions [Goldie] |
| 24002 | We over-estimate the role of character traits when explaining behaviour [Goldie] |
| 24004 | Psychologists suggest we are muddled about traits, and maybe they should be abandoned [Goldie] |
| 23993 | Our capabilities did not all evolve during the hunter gathering period [Goldie] |