105 ideas
| 11912 | Substantive metaphysics says what a property is, not what a predicate means [Molnar] |
| 11920 | A real definition gives all the properties that constitute an identity [Molnar] |
| 15413 | With four tense operators, all complex tenses reduce to fourteen basic cases [Burgess] |
| 15415 | The temporal Barcan formulas fix what exists, which seems absurd [Burgess] |
| 15430 | Is classical logic a part of intuitionist logic, or vice versa? [Burgess] |
| 15431 | It is still unsettled whether standard intuitionist logic is complete [Burgess] |
| 15429 | Relevance logic's → is perhaps expressible by 'if A, then B, for that reason' [Burgess] |
| 15945 | Second-order set theory just adds a version of Replacement that quantifies over functions [Lavine] |
| 15914 | An 'upper bound' is the greatest member of a subset; there may be several of these, so there is a 'least' one [Lavine] |
| 15921 | Collections of things can't be too big, but collections by a rule seem unlimited in size [Lavine] |
| 15937 | Those who reject infinite collections also want to reject the Axiom of Choice [Lavine] |
| 15936 | The Power Set is just the collection of functions from one collection to another [Lavine] |
| 15899 | Replacement was immediately accepted, despite having very few implications [Lavine] |
| 15930 | Foundation says descending chains are of finite length, blocking circularity, or ungrounded sets [Lavine] |
| 15920 | Pure collections of things obey Choice, but collections defined by a rule may not [Lavine] |
| 15898 | The controversy was not about the Axiom of Choice, but about functions as arbitrary, or given by rules [Lavine] |
| 15919 | The 'logical' notion of class has some kind of definition or rule to characterise the class [Lavine] |
| 15900 | The iterative conception of set wasn't suggested until 1947 [Lavine] |
| 15931 | The iterative conception needs the Axiom of Infinity, to show how far we can iterate [Lavine] |
| 15932 | The iterative conception doesn't unify the axioms, and has had little impact on mathematical proofs [Lavine] |
| 15933 | Limitation of Size: if it's the same size as a set, it's a set; it uses Replacement [Lavine] |
| 15913 | A collection is 'well-ordered' if there is a least element, and all of its successors can be identified [Lavine] |
| 15404 | Technical people see logic as any formal system that can be studied, not a study of argument validity [Burgess] |
| 15405 | Classical logic neglects the non-mathematical, such as temporality or modality [Burgess] |
| 15427 | The Cut Rule expresses the classical idea that entailment is transitive [Burgess] |
| 15421 | Classical logic neglects counterfactuals, temporality and modality, because maths doesn't use them [Burgess] |
| 15926 | Second-order logic presupposes a set of relations already fixed by the first-order domain [Lavine] |
| 15403 | Philosophical logic is a branch of logic, and is now centred in computer science [Burgess] |
| 15934 | Mathematical proof by contradiction needs the law of excluded middle [Lavine] |
| 15407 | Formalising arguments favours lots of connectives; proving things favours having very few [Burgess] |
| 15424 | Asserting a disjunction from one disjunct seems odd, but can be sensible, and needed in maths [Burgess] |
| 15409 | All occurrences of variables in atomic formulas are free [Burgess] |
| 15414 | The denotation of a definite description is flexible, rather than rigid [Burgess] |
| 15406 | 'Induction' and 'recursion' on complexity prove by connecting a formula to its atomic components [Burgess] |
| 15425 | The sequent calculus makes it possible to have proof without transitivity of entailment [Burgess] |
| 15426 | We can build one expanding sequence, instead of a chain of deductions [Burgess] |
| 15408 | 'Tautologies' are valid formulas of classical sentential logic - or substitution instances in other logics [Burgess] |
| 15418 | Validity (for truth) and demonstrability (for proof) have correlates in satisfiability and consistency [Burgess] |
| 15412 | Models leave out meaning, and just focus on truth values [Burgess] |
| 15411 | We only need to study mathematical models, since all other models are isomorphic to these [Burgess] |
| 15416 | We aim to get the technical notion of truth in all models matching intuitive truth in all instances [Burgess] |
| 15428 | The Liar seems like a truth-value 'gap', but dialethists see it as a 'glut' [Burgess] |
| 15907 | Mathematics is nowadays (thanks to set theory) regarded as the study of structure, not of quantity [Lavine] |
| 15942 | Every rational number, unlike every natural number, is divisible by some other number [Lavine] |
| 15922 | For the real numbers to form a set, we need the Continuum Hypothesis to be true [Lavine] |
| 18250 | Cauchy gave a necessary condition for the convergence of a sequence [Lavine] |
| 15904 | The two sides of the Cut are, roughly, the bounding commensurable ratios [Lavine] |
| 15912 | Counting results in well-ordering, and well-ordering makes counting possible [Lavine] |
| 15949 | The theory of infinity must rest on our inability to distinguish between very large sizes [Lavine] |
| 15947 | The infinite is extrapolation from the experience of indefinitely large size [Lavine] |
| 15940 | The intuitionist endorses only the potential infinite [Lavine] |
| 15909 | 'Aleph-0' is cardinality of the naturals, 'aleph-1' the next cardinal, 'aleph-ω' the ω-th cardinal [Lavine] |
| 15915 | Ordinals are basic to Cantor's transfinite, to count the sets [Lavine] |
| 15917 | Paradox: the class of all ordinals is well-ordered, so must have an ordinal as type - giving a bigger ordinal [Lavine] |
| 15918 | Paradox: there is no largest cardinal, but the class of everything seems to be the largest [Lavine] |
| 10185 | Set theory is the standard background for modern mathematics [Burgess] |
| 15929 | Set theory will found all of mathematics - except for the notion of proof [Lavine] |
| 10184 | Structuralists take the name 'R' of the reals to be a variable ranging over structures, not a structure [Burgess] |
| 10189 | There is no one relation for the real number 2, as relations differ in different models [Burgess] |
| 10186 | If set theory is used to define 'structure', we can't define set theory structurally [Burgess] |
| 10187 | Abstract algebra concerns relations between models, not common features of all the models [Burgess] |
| 10188 | How can mathematical relations be either internal, or external, or intrinsic? [Burgess] |
| 15935 | Modern mathematics works up to isomorphism, and doesn't care what things 'really are' [Lavine] |
| 15928 | Intuitionism rejects set-theory to found mathematics [Lavine] |
| 11919 | Ontological dependence rests on essential connection, not necessary connection [Molnar] |
| 11929 | The three categories in ontology are objects, properties and relations [Molnar] |
| 11927 | Reflexive relations are syntactically polyadic but ontologically monadic [Molnar] |
| 11915 | If atomism is true, then all properties derive from ultimate properties [Molnar] |
| 11916 | 'Being physical' is a second-order property [Molnar] |
| 11956 | 'Categorical properties' are those which are not powers [Molnar] |
| 11928 | Are tropes transferable? If they are, that is a version of Platonism [Molnar] |
| 11933 | A power's type-identity is given by its definitive manifestation [Molnar] |
| 11932 | Powers have Directedness, Independence, Actuality, Intrinsicality and Objectivity [Molnar] |
| 11934 | The physical world has a feature very like mental intentionality [Molnar] |
| 11947 | Dispositions and external powers arise entirely from intrinsic powers in objects [Molnar] |
| 11952 | The Standard Model suggest that particles are entirely dispositional, and hence are powers [Molnar] |
| 11953 | Some powers are ungrounded, and others rest on them, and are derivative [Molnar] |
| 11943 | Dispositions can be causes, so they must be part of the actual world [Molnar] |
| 11939 | If powers only exist when actual, they seem to be nomadic, and indistinguishable from non-powers [Molnar] |
| 11914 | Platonic explanations of universals actually diminish our understanding [Molnar] |
| 11913 | For nominalists, predicate extensions are inexplicable facts [Molnar] |
| 11962 | Nominalists only accept first-order logic [Molnar] |
| 11917 | Structural properties are derivate properties [Molnar] |
| 11955 | There are no 'structural properties', as properties with parts [Molnar] |
| 11918 | The essence of a thing need not include everything that is necessarily true of it [Molnar] |
| 15420 | De re modality seems to apply to objects a concept intended for sentences [Burgess] |
| 15419 | General consensus is S5 for logical modality of validity, and S4 for proof [Burgess] |
| 15417 | Logical necessity has two sides - validity and demonstrability - which coincide in classical logic [Burgess] |
| 11963 | What is the truthmaker for a non-existent possible? [Molnar] |
| 15423 | It is doubtful whether the negation of a conditional has any clear meaning [Burgess] |
| 15422 | Three conditionals theories: Materialism (material conditional), Idealism (true=assertable), Nihilism (no truth) [Burgess] |
| 11951 | Hume allows interpolation, even though it and extrapolation are not actually valid [Molnar] |
| 11936 | The two ways proposed to distinguish mind are intentionality or consciousness [Molnar] |
| 11935 | Physical powers like solubility and charge also have directedness [Molnar] |
| 11944 | Rule occasionalism says God's actions follow laws, not miracles [Molnar] |
| 11960 | Singular causation is prior to general causation; each aspirin produces the aspirin generalization [Molnar] |
| 11937 | We should analyse causation in terms of powers, not vice versa [Molnar] |
| 11954 | We should analyse causation in terms of powers [Molnar] |
| 11961 | Causal dependence explains counterfactual dependence, not vice versa [Molnar] |
| 11959 | Science works when we assume natural kinds have essences - because it is true [Molnar] |
| 9448 | Location in space and time are non-power properties [Molnar, by Mumford] |
| 11930 | One essential property of a muon doesn't entail the others [Molnar] |
| 11957 | It is contingent which kinds and powers exist in the world [Molnar] |
| 11921 | The laws of nature depend on the powers, not the other way round [Molnar] |
| 11931 | Energy fields are discontinuous at the very small [Molnar] |