75 ideas
| 5333 | Philosophy needs wisdom about who we are, as well as how we ought to be [Flanagan] |
| 5334 | We resist science partly because it can't provide ethical wisdom [Flanagan] |
| 9331 | How do we determine which of the sentences containing a term comprise its definition? [Horwich] |
| 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] |
| 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] |
| 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] |
| 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] |
| 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] |
| 9333 | A priori belief is not necessarily a priori justification, or a priori knowledge [Horwich] |
| 9342 | Understanding needs a priori commitment [Horwich] |
| 9332 | Meaning is generated by a priori commitment to truth, not the other way around [Horwich] |
| 9341 | Meanings and concepts cannot give a priori knowledge, because they may be unacceptable [Horwich] |
| 9334 | If we stipulate the meaning of 'number' to make Hume's Principle true, we first need Hume's Principle [Horwich] |
| 9339 | A priori knowledge (e.g. classical logic) may derive from the innate structure of our minds [Horwich] |
| 5340 | Explanation does not entail prediction [Flanagan] |
| 5346 | In the 17th century a collisionlike view of causation made mental causation implausible [Flanagan] |
| 5341 | Only you can have your subjective experiences because only you are hooked up to your nervous system [Flanagan] |
| 5351 | We only have a sense of our self as continuous, not as exactly the same [Flanagan] |
| 5353 | The self is an abstraction which magnifies important aspects of autobiography [Flanagan] |
| 5354 | We are not born with a self; we develop a self through living [Flanagan] |
| 5349 | For Buddhists a fixed self is a morally dangerous illusion [Flanagan] |
| 5338 | Normal free will claims control of what I do, but a stronger view claims control of thought and feeling [Flanagan] |
| 5344 | Free will is held to give us a whole list of desirable capacities for living [Flanagan] |
| 5332 | People believe they have free will that circumvents natural law, but only an incorporeal mind could do this [Flanagan] |
| 5345 | We only think of ourselves as having free will because we first thought of God that way [Flanagan] |
| 5343 | People largely came to believe in dualism because it made human agents free [Flanagan] |
| 5347 | Behaviourism notoriously has nothing to say about mental causation [Flanagan] |
| 5339 | Cars and bodies obey principles of causation, without us knowing any 'strict laws' about them [Flanagan] |
| 5342 | Physicalism doesn't deny that the essence of an experience is more than its neural realiser [Flanagan] |
| 5335 | Emotions are usually very apt, rather than being non-rational and fickle [Flanagan] |
| 5348 | Intellectualism admires the 'principled actor', non-intellectualism admires the 'good character' [Flanagan] |
| 5355 | Cognitivists think morals are discovered by reason [Flanagan] |
| 5336 | Ethics is the science of the conditions that lead to human flourishing [Flanagan] |
| 5350 | The Hindu doctrine of reincarnation only appeared in the eighth century CE [Flanagan] |
| 5352 | The idea of the soul gets some support from the scientific belief in essential 'natural kinds' [Flanagan] |