114 ideas
| 23890 | For Plato true wisdom is supernatural [Plato, by Weil] |
| 3060 | Plato never mentions Democritus, and wished to burn his books [Plato, by Diog. Laertius] |
| 16227 | Philosophers are good at denying the obvious [Hawley] |
| 23891 | Two contradictories force us to find a relation which will correlate them [Plato, by Weil] |
| 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] |
| 16216 | Part of the sense of a proper name is a criterion of the thing's identity [Hawley] |
| 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] |
| 16211 | A homogeneous rotating disc should be undetectable according to Humean supervenience [Hawley] |
| 16219 | Non-linguistic things cannot be indeterminate, because they don't have truth-values at all [Hawley] |
| 16223 | Maybe for the world to be vague, it must be vague in its foundations? [Hawley] |
| 16226 | Epistemic vagueness seems right in the case of persons [Hawley] |
| 16208 | Supervaluation refers to one vaguely specified thing, through satisfaction by everything in some range [Hawley] |
| 16221 | Supervaluationism takes what the truth-value would have been if indecision was resolved [Hawley] |
| 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] |
| 14502 | Plato's idea of 'structure' tends to be mathematically expressed [Plato, by Koslicki] |
| 16230 | Maybe the only properties are basic ones like charge, mass and spin [Hawley] |
| 3039 | When Diogenes said he could only see objects but not their forms, Plato said it was because he had eyes but no intellect [Plato, by Diog. Laertius] |
| 20906 | Platonists argue for the indivisible triangle-in-itself [Plato, by Aristotle] |
| 17948 | Plato's Forms meant that the sophists only taught the appearance of wisdom and virtue [Plato, by Nehamas] |
| 556 | If there is one Form for both the Form and its participants, they must have something in common [Aristotle on Plato] |
| 563 | If gods are like men, they are just eternal men; similarly, Forms must differ from particulars [Aristotle on Plato] |
| 557 | A Form is a cause of things only in the way that white mixed with white is a cause [Aristotle on Plato] |
| 565 | The Forms cannot be changeless if they are in changing things [Aristotle on Plato] |
| 16232 | An object is 'natural' if its stages are linked by certain non-supervenient relations [Hawley] |
| 9607 | The greatest discovery in human thought is Plato's discovery of abstract objects [Brown,JR on Plato] |
| 13263 | We can grasp whole things in science, because they have a mathematics and a teleology [Plato, by Koslicki] |
| 13261 | Plato sees an object's structure as expressible in mathematics [Plato, by Koslicki] |
| 13265 | Plato was less concerned than Aristotle with the source of unity in a complex object [Plato, by Koslicki] |
| 593 | Plato's holds that there are three substances: Forms, mathematical entities, and perceptible bodies [Plato, by Aristotle] |
| 16200 | Are sortals spatially maximal - so no cat part is allowed to be a cat? [Hawley] |
| 16237 | The modal features of statue and lump are disputed; when does it stop being that statue? [Hawley] |
| 16238 | Perdurantists can adopt counterpart theory, to explain modal differences of identical part-sums [Hawley] |
| 16220 | Vagueness is either in our knowledge, in our talk, or in reality [Hawley] |
| 16222 | Indeterminacy in objects and in properties are not distinct cases [Hawley] |
| 16228 | The constitution theory is endurantism plus more than one object in a place [Hawley] |
| 16229 | Constitution theory needs sortal properties like 'being a sweater' to distinguish it from its thread [Hawley] |
| 14492 | If the constitution view says thread and sweater are two things, why do we talk of one thing? [Hawley] |
| 13260 | Plato says wholes are either containers, or they're atomic, or they don't exist [Plato, by Koslicki] |
| 11237 | Only universals have essence [Plato, by Politis] |
| 11238 | Plato and Aristotle take essence to make a thing what it is [Plato, by Politis] |
| 16193 | 'Adverbialism' explains change by saying an object has-at-some-time a given property [Hawley] |
| 16195 | Presentism solves the change problem: the green banana ceases, so can't 'relate' to the yellow one [Hawley] |
| 16202 | The problem of change arises if there must be 'identity' of a thing over time [Hawley] |
| 16192 | Endurance theory can relate properties to times, or timed instantiations to properties [Hawley] |
| 16196 | Endurance is a sophisticated theory, covering properties, instantiation and time [Hawley] |
| 16197 | How does perdurance theory explain our concern for our own future selves? [Hawley] |
| 16191 | Perdurance needs an atemporal perspective, to say that the object 'has' different temporal parts [Hawley] |
| 16199 | If an object is the sum of all of its temporal parts, its mass is staggeringly large! [Hawley] |
| 16201 | Perdurance says things are sums of stages; Stage Theory says each stage is the thing [Hawley] |
| 16240 | If a life is essentially the sum of its temporal parts, it couldn't be shorter or longer than it was? [Hawley] |
| 16203 | Stage Theory seems to miss out the link between stages of the same object [Hawley] |
| 16204 | Stage Theory says every stage is a distinct object, which gives too many objects [Hawley] |
| 16212 | An isolated stage can't be a banana (which involves suitable relations to other stages) [Hawley] |
| 16213 | Stages of one thing are related by extrinsic counterfactual and causal relations [Hawley] |
| 16206 | Stages must be as fine-grained in length as change itself, so any change is a new stage [Hawley] |
| 16205 | The stages of Stage Theory seem too thin to populate the world, or to be referred to [Hawley] |
| 13702 | The identity of indiscernibles is necessarily true, if being a member of some set counts as a property [Sider] |
| 16225 | If two things might be identical, there can't be something true of one and false of the other [Hawley] |
| 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] |
| 16239 | To decide whether something is a counterpart, we need to specify a relevant sortal concept [Hawley] |
| 13719 | Barcan Formula problem: there might have been a ghost, despite nothing existing which could be a ghost [Sider] |
| 17085 | A good explanation totally rules out the opposite explanation (so Forms are required) [Plato, by Ruben] |
| 16218 | On any theory of self, it is hard to explain why we should care about our future selves [Hawley] |
| 1651 | Plato wanted to somehow control and purify the passions [Vlastos on Plato] |
| 3324 | Plato's whole philosophy may be based on being duped by reification - a figure of speech [Benardete,JA on Plato] |
| 7503 | Plato never refers to examining the conscience [Plato, by Foucault] |
| 2173 | As religion and convention collapsed, Plato sought morals not just in knowledge, but in the soul [Williams,B on Plato] |
| 9274 | Plato's legacy to European thought was the Good, the Beautiful and the True [Plato, by Gray] |
| 94 | Pleasure is better with the addition of intelligence, so pleasure is not the good [Plato, by Aristotle] |
| 17947 | Plato decided that the virtuous and happy life was the philosophical life [Plato, by Nehamas] |
| 6015 | Plato, unusually, said that theoretical and practical wisdom are inseparable [Plato, by Kraut] |
| 2912 | Plato is boring [Nietzsche on Plato] |
| 16215 | Causation is nothing more than the counterfactuals it grounds? [Hawley] |
| 1526 | Almost everyone except Plato thinks that time could not have been generated [Plato, by Aristotle] |
| 16207 | Time could be discrete (like integers) or dense (rationals) or continuous (reals) [Hawley] |