86 ideas
23350 | A wise philosophers uses reason to cautiously judge each aspect of living [Epictetus] |
23355 | The task of philosophy is to establish standards, as occurs with weights and measures [Epictetus] |
21394 | Philosophy is knowing each logos, how they fit together, and what follows from them [Epictetus] |
20876 | Philosophy investigates the causes of disagreements, and seeks a standard for settling them [Epictetus] |
23344 | Reason itself must be compounded from some of our impressions [Epictetus] |
23343 | Because reason performs all analysis, we should analyse reason - but how? [Epictetus] |
9355 | One sort of circularity presupposes a premise, the other presupposes a rule being used [Braithwaite, by Devitt] |
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] |
13710 | In D we add that 'what is necessary is possible'; then tautologies are possible, and contradictions not necessary [Sider] |
13706 | Intuitively, deontic accessibility seems not to be reflexive, but to be serial [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] |
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] |
13680 | Maybe logical consequence is a primitive notion [Sider] |
13679 | Maybe logical consequence is more a matter of provability than of truth-preservation [Sider] |
13678 | The most popular account of logical consequence is the semantic or model-theoretic one [Sider] |
13682 | Maybe logical consequence is impossibility of the premises being true and the consequent false [Sider] |
13722 | A 'theorem' is an axiom, or the last line of a legitimate proof [Sider] |
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] |
13703 | λ can treat 'is cold and hungry' as a single predicate [Sider] |
13687 | No assumptions in axiomatic proofs, so no conditional proof or reductio [Sider] |
13688 | Good axioms should be indisputable logical truths [Sider] |
13691 | Induction has a 'base case', then an 'inductive hypothesis', and then the 'inductive step' [Sider] |
13690 | Proof by induction 'on the length of the formula' deconstructs a formula into its accepted atoms [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] |
13693 | A 'supervaluation' assigns further Ts and Fs, if they have been assigned in every precisification [Sider] |
13695 | Supervaluational logic is classical, except when it adds the 'Definitely' operator [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] |
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] |
23359 | We can't believe apparent falsehoods, or deny apparent truths [Epictetus] |
23356 | Self-evidence is most obvious when people who deny a proposition still have to use it [Epictetus] |
23330 | Freedom is making all things happen by choice, without constraint [Epictetus] |
23342 | Freedom is acting by choice, with no constraint possible [Epictetus] |
23329 | We make progress when we improve and naturalise our choices, asserting their freedom [Epictetus] |
23332 | Zeus gave me a nature which is free (like himself) from all compulsion [Epictetus] |
23331 | Not even Zeus can control what I choose [Epictetus] |
23338 | You can fetter my leg, but not even Zeus can control my power of choice [Epictetus] |
20875 | If we could foresee the future, we should collaborate with disease and death [Epictetus] |
23347 | If I know I am fated to be ill, I should want to be ill [Epictetus] |
23325 | Epictetus developed a notion of will as the source of our responsibility [Epictetus, by Frede,M] |
20873 | Tragedies are versified sufferings of people impressed by externals [Epictetus] |
23364 | Homer wrote to show that the most blessed men can be ruined by poor judgement [Epictetus] |
23340 | We consist of animal bodies and god-like reason [Epictetus] |
23358 | Every species produces exceptional beings, and we must just accept their nature [Epictetus] |
23339 | I will die as becomes a person returning what he does not own [Epictetus] |
23345 | Don't be frightened of pain or death; only be frightened of fearing them [Epictetus] |
23357 | Knowledge of what is good leads to love; only the wise, who distinguish good from evil, can love [Epictetus] |
23363 | The evil for everything is what is contrary to its nature [Epictetus] |
23328 | The essences of good and evil are in dispositions to choose [Epictetus] |
23362 | All human ills result from failure to apply preconceptions to particular cases [Epictetus] |
23353 | We have a natural sense of honour [Epictetus] |
23354 | If someone harms themselves in harming me, then I harm myself by returning the harm [Epictetus] |
23324 | In the Discourses choice [prohairesis] defines our character and behaviour [Epictetus, by Frede,M] |
23361 | Health is only a good when it is used well [Epictetus] |
23346 | A person is as naturally a part of a city as a foot is part of the body [Epictetus] |
23351 | We are citizens of the universe, and principal parts of it [Epictetus] |
23352 | A citizen should only consider what is good for the whole society [Epictetus] |
20874 | A citizen is committed to ignore private advantage, and seek communal good [Epictetus] |
22604 | Punishing a criminal for moral ignorance is the same as punishing someone for being blind [Epictetus] |
23349 | Asses are born to carry human burdens, not as ends in themselves [Epictetus] |
23341 | God created humans as spectators and interpreters of God's works [Epictetus] |
23348 | Both god and the good bring benefits, so their true nature seems to be the same [Epictetus] |
23360 | Each of the four elements in you is entirely scattered after death [Epictetus] |