Combining Philosophers

All the ideas for Roderick Firth, Susan A. Gelman and Volker Halbach

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90 ideas

1. Philosophy / F. Analytic Philosophy / 5. Linguistic Analysis
Analysis rests on natural language, but its ideal is a framework which revises language [Halbach]
     Full Idea: For me, although the enterprise of philosophical analysis is driven by natural language, its goal is not a linguistic analysis of English but rather an expressively strong framework that may at best be seen as a revision of English.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 12)
     A reaction: I agree, but the problem is that there are different ideals for the revision, which may be in conflict. Logicians, mathematicians, metaphysicians, scientists, moralists and aestheticians are queueing up to improve in their own way.
2. Reason / D. Definition / 2. Aims of Definition
An explicit definition enables the elimination of what is defined [Halbach]
     Full Idea: Explicit definitions allow for a complete elimination of the defined notion (at least in extensional contexts).
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 1)
     A reaction: If the context isn't extensional (concerning the things themselves) then we could define one description of it, but be unable to eliminate it under another description. Elimination is no the aim of an Aristotelian definition. Halbach refers to truth.
2. Reason / E. Argument / 3. Analogy
Don't trust analogies; they are no more than a guideline [Halbach]
     Full Idea: Arguments from analogy are to be distrusted: at best they can serve as heuristics.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 4)
3. Truth / A. Truth Problems / 1. Truth
Truth-value 'gluts' allow two truth values together; 'gaps' give a partial conception of truth [Halbach]
     Full Idea: Truth-value 'gluts' correspond to a so-called dialethic conception of truth; excluding gluts and admitting only 'gaps' leads to a conception of what is usually called 'partial' truth.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 15.2)
     A reaction: Talk of 'gaps' and 'gluts' seem to be the neatest way of categorising views of truth. I want a theory with no gaps or gluts.
Truth axioms prove objects exist, so truth doesn't seem to be a logical notion [Halbach]
     Full Idea: Two typed disquotation sentences, truth axioms of TB, suffice for proving that there at least two objects. Hence truth is not a logical notion if one expects logical notions to be ontologically neutral.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 21.2)
3. Truth / A. Truth Problems / 2. Defining Truth
Any definition of truth requires a metalanguage [Halbach]
     Full Idea: It is plain that the distinction between object and metalanguage is required for the definability of truth.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 11)
     A reaction: Halbach's axiomatic approach has given up on definability, and therefore it can seek to abandon the metalanguage and examine 'type-free' theories.
Truth definitions don't produce a good theory, because they go beyond your current language [Halbach]
     Full Idea: It is far from clear that a definition of truth can lead to a philosophically satisfactory theory of truth. Tarski's theorem on the undefinability of the truth predicate needs resources beyond those of the language for which it is being defined.
     From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1)
     A reaction: The idea is that you need a 'metalanguage' for the definition. If I say 'p' is a true sentence in language 'L', I am not making that observation from within language L. The dream is a theory confined to the object language.
Traditional definitions of truth often make it more obscure, rather than less [Halbach]
     Full Idea: A common complaint against traditional definitional theories of truth is that it is far from clear that the definiens is not more in need of clarification than the definiendum (that is, the notion of truth).
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 1)
     A reaction: He refers to concepts like 'correspondence', 'facts', 'coherence' or 'utility', which are said to be trickier to understand than 'true'. I suspect that philosophers like Halbach confuse 'clear' with 'precise'. Coherence is quite clear, but imprecise.
If people have big doubts about truth, a definition might give it more credibility [Halbach]
     Full Idea: If one were wondering whether truth should be considered a legitimate notion at all, a definition might be useful in dispersing doubts about its legitimacy.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 3)
     A reaction: Halbach is proposing to skip definitions, and try to give rules for using 'true' instead, but he doesn't rule out definitions. A definition of 'knowledge' or 'virtue' or 'democracy' might equally give those credibility.
3. Truth / F. Semantic Truth / 1. Tarski's Truth / c. Meta-language for truth
In semantic theories of truth, the predicate is in an object-language, and the definition in a metalanguage [Halbach]
     Full Idea: In semantic theories of truth (Tarski or Kripke), a truth predicate is defined for an object-language. This definition is carried out in a metalanguage, which is typically taken to include set theory or another strong theory or expressive language.
     From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1)
     A reaction: Presumably the metalanguage includes set theory because that connects it with mathematics, and enables it to be formally rigorous. Tarski showed, in his undefinability theorem, that the meta-language must have increased resources.
Semantic theories avoid Tarski's Theorem by sticking to a sublanguage [Halbach]
     Full Idea: In semantic theories (e.g.Tarski's or Kripke's), a definition evades Tarski's Theorem by restricting the possible instances in the schema T[φ]↔φ to sentences of a proper sublanguage of the language formulating the equivalences.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 1)
     A reaction: The schema says if it's true it's affirmable, and if it's affirmable it's true. The Liar Paradox is a key reason for imposing this restriction.
3. Truth / F. Semantic Truth / 2. Semantic Truth
Disquotational truth theories are short of deductive power [Halbach]
     Full Idea: The problem of restricted deductive power has haunted disquotational theories of truth (…because they can't prove generalisations).
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 19.5)
3. Truth / G. Axiomatic Truth / 1. Axiomatic Truth
Axiomatic theories of truth need a weak logical framework, and not a strong metatheory [Halbach]
     Full Idea: Axiomatic theories of truth can be presented within very weak logical frameworks which require very few resources, and avoid the need for a strong metalanguage and metatheory.
     From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1)
CT proves PA consistent, which PA can't do on its own, so CT is not conservative over PA [Halbach]
     Full Idea: Compositional Truth CT proves the consistency of Peano arithmetic, which is not provable in Peano arithmetic by Gödel's second incompleteness theorem. Hence the theory CT is not conservative over Peano arithmetic.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 8.6)
If truth is defined it can be eliminated, whereas axiomatic truth has various commitments [Halbach]
     Full Idea: If truth can be explicitly defined, it can be eliminated, whereas an axiomatized notion of truth may bring all kinds of commitments.
     From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1.3)
     A reaction: The general principle that anything which can be defined can be eliminated (in an abstract theory, presumably, not in nature!) raises interesting questions about how many true theories there are which are all equivalent to one another.
Axiomatic truth doesn't presuppose a truth-definition, though it could admit it at a later stage [Halbach]
     Full Idea: Choosing an axiomatic approach to truth might well be compatible with the view that truth is definable; the definability of truth is just not presupposed at the outset.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 1)
     A reaction: Is it possible that a successful axiomatisation is a successful definition?
The main semantic theories of truth are Kripke's theory, and revisions semantics [Halbach]
     Full Idea: Revision semantics is arguably the main competitor of Kripke's theory of truth among semantic truth theories. …In the former one may hope through revision to arrive at better and better models, ..sorting out unsuitable extensions of the truth predicate.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 14)
     A reaction: Halbach notes later that Kripke's theory (believe it or not) is considerably simpler than revision semantics.
To axiomatise Tarski's truth definition, we need a binary predicate for his 'satisfaction' [Halbach]
     Full Idea: If the clauses of Tarski's definition of truth are turned into axioms (as Davidson proposed) then a primitive binary predicate symbol for satisfaction is needed, as Tarski defined truth in terms of satisfaction. Standard language has a unary predicate.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 5.2)
Compositional Truth CT has the truth of a sentence depending of the semantic values of its constituents [Halbach]
     Full Idea: In the typed Compositional Truth theory CT, it is compositional because the truth of a sentence depends on the semantic values of the constituents of that sentence.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 8)
     A reaction: [axioms on p. 65 of Halbach]
Gödel numbering means a theory of truth can use Peano Arithmetic as its base theory [Halbach]
     Full Idea: Often syntactic objects are identified with their numerical codes. …Expressions of a countable formal language can be coded in the natural numbers. This allows a theory of truth to use Peano Arithmetic (with its results) as a base theory.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 2)
     A reaction: The numbering system is the famous device invented by Gödel for his great proof of incompleteness. This idea is a key to understanding modern analytic philosophy. It is the bridge which means philosophical theories can be treated mathematically.
Truth axioms need a base theory, because that is where truth issues arise [Halbach]
     Full Idea: Considering the truth axioms in the absence of a base theory is not very sensible because characteristically truth theoretic reasoning arises from the interplay of the truth axioms with the base theory.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 21.2)
     A reaction: The base theory usually seems to be either Peano arithmetic or set theory. We might say that introverted thought (e.g. in infants) has little use for truth; it is when you think about the world that truth becomes a worry.
We know a complete axiomatisation of truth is not feasible [Halbach]
     Full Idea: In the light of incompleteness phenomena, one should not expect a categorical axiomatisation of truth to be feasible, but this should not keep one from studying axiomatic theories of truth (or of arithmetic).
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 3)
     A reaction: This, of course, is because of Gödel's famous results. It is important to be aware in this field that there cannot be a dream of a final theory, so we are just seeing what can be learned about truth.
A theory is 'conservative' if it adds no new theorems to its base theory [Halbach, by PG]
     Full Idea: A truth theory is 'conservative' if the addition of the truth predicate does not add any new theorems to the base theory.
     From: report of Volker Halbach (Axiomatic Theories of Truth [2011], 6 Df 6.6) by PG - Db (ideas)
     A reaction: Halbach presents the definition more formally, and this is my attempt at getting it into plain English. Halbach uses Peano Arithmetic as his base theory, but set theory is also sometimes used.
The Tarski Biconditional theory TB is Peano Arithmetic, plus truth, plus all Tarski bi-conditionals [Halbach]
     Full Idea: The truth theory TB (Tarski Biconditional) is all the axioms of Peano Arithmetic, including all instances of the induction schema with the truth predicate, plus all the sentences of the form T[φ] ↔ φ.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 7)
     A reaction: The biconditional formula is the famous 'snow is white' iff snow is white. The truth of the named sentence is equivalent to asserting the sentence. This is a typed theory of truth, and it is conservative over PA.
Theories of truth are 'typed' (truth can't apply to sentences containing 'true'), or 'type-free' [Halbach]
     Full Idea: I sort theories of truth into the large families of 'typed' and 'type-free'. Roughly, typed theories prohibit a truth predicate's application to sentences with occurrences of that predicate, and one cannot prove the truth of sentences containing 'true'.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], II Intro)
     A reaction: The problem sentence the typed theories are terrified of is the Liar Sentence. Typing produces a hierarchy of languages, referring down to the languages below them.
Should axiomatic truth be 'conservative' - not proving anything apart from implications of the axioms? [Halbach]
     Full Idea: If truth is not explanatory, truth axioms should not allow proof of new theorems not involving the truth predicate. It is hence said that axiomatic truth should be 'conservative' - not implying further sentences beyond what the axioms can prove.
     From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1.3)
     A reaction: [compressed]
Instead of a truth definition, add a primitive truth predicate, and axioms for how it works [Halbach]
     Full Idea: The axiomatic approach does not presuppose that truth can be defined. Instead, a formal language is expanded by a new primitive predicate of truth, and axioms for that predicate are then laid down.
     From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1)
     A reaction: Idea 15647 explains why Halbach thinks the definition route is no good.
3. Truth / G. Axiomatic Truth / 2. FS Truth Axioms
Friedman-Sheard is type-free Compositional Truth, with two inference rules for truth [Halbach]
     Full Idea: The Friedman-Sheard truth system FS is based on compositional theory CT. The axioms of FS are obtained by relaxing the type restriction on the CT-axioms, and adding rules inferring sentences from their truth, and vice versa.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 15)
     A reaction: The rules are called NEC and CONEC by Halbach. The system FSN is FS without the two rules.
3. Truth / G. Axiomatic Truth / 3. KF Truth Axioms
The KF is much stronger deductively than FS, which relies on classical truth [Halbach]
     Full Idea: The Kripke-Feferman theory is relatively deductively very strong. In particular, it is much stronger than its competitor FS, which is based on a completely classical notion of truth.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 15.3)
The KF theory is useful, but it is not a theory containing its own truth predicate [Halbach]
     Full Idea: KF is useful for explicating Peano arithmetic, but it certainly does not come to close to being a theory that contains its own truth predicate.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 16)
     A reaction: Since it is a type-free theory, its main philosophical aspiration was to contain its own truth predicate, so that is bad news (for philosophers).
Kripke-Feferman theory KF axiomatises Kripke fixed-points, with Strong Kleene logic with gluts [Halbach]
     Full Idea: The Kripke-Feferman theory KF is an axiomatisation of the fixed points of an operator, that is, of a Kripkean fixed-point semantics with the Strong Kleene evaluation schema with truth-value gluts.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 15.1)
3. Truth / H. Deflationary Truth / 2. Deflationary Truth
Some say deflationism is axioms which are conservative over the base theory [Halbach]
     Full Idea: Some authors have tried to understand the deflationist claim that truth is not a substantial notion as the claim that a satisfactory axiomatisation of truth should be conservative over the base theory.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 8)
Deflationists say truth merely serves to express infinite conjunctions [Halbach]
     Full Idea: According to many deflationists, truth serves merely the purpose of expressing infinite conjunctions.
     From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1.3)
     A reaction: That is, it asserts sentences that are too numerous to express individually. It also seems, on a deflationist view, to serve for anaphoric reference to sentences, such as 'what she just said is true'.
Deflationism says truth is a disquotation device to express generalisations, adding no new knowledge [Halbach]
     Full Idea: There are two doctrines at the core of deflationism. The first says truth is a device of disquotation used to express generalisations, and the second says truth is a thin notion that contributes nothing to our knowledge of the world
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 21)
The main problem for deflationists is they can express generalisations, but not prove them [Halbach]
     Full Idea: The main criticism that deflationist theories based on the disquotation sentences or similar axioms have to meet was raised by Tarski: the disquotation sentences do not allow one to prove generalisations.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 7)
Deflationists say truth is just for expressing infinite conjunctions or generalisations [Halbach]
     Full Idea: Deflationists do not hold that truth is completely dispensable. They claim that truth serves the purpose of expressing infinite conjunctions or generalisations.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 7)
     A reaction: It is also of obvious value as a shorthand in ordinary conversation, but rigorous accounts can paraphrase that out. 'What he said is true'. 'Pick out the true sentences from p,q,r and s' seems to mean 'affirm some of them'. What does 'affirm' mean?
Compositional Truth CT proves generalisations, so is preferred in discussions of deflationism [Halbach]
     Full Idea: Compositional Truth CT and its variants has desirable generalisations among its logical consequences, so they seem to have ousted purely disquotational theories such as TB in the discussion on deflationism.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 8)
4. Formal Logic / E. Nonclassical Logics / 3. Many-Valued Logic
In Strong Kleene logic a disjunction just needs one disjunct to be true [Halbach]
     Full Idea: In Strong Kleene logic a disjunction of two sentences is true if at least one disjunct is true, even when the other disjunct lacks a truth value.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 18)
     A reaction: This sounds fine to me. 'Either I'm typing this or Homer had blue eyes' comes out true in any sensible system.
In Weak Kleene logic there are 'gaps', neither true nor false if one component lacks a truth value [Halbach]
     Full Idea: In Weak Kleene Logic, with truth-value gaps, a sentence is neither true nor false if one of its components lacks a truth value. A line of the truth table shows a gap if there is a gap anywhere in the line, and the other lines are classical.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 18)
     A reaction: This will presumably apply even if the connective is 'or', so a disjunction won't be true, even if one disjunct is true, when the other disjunct is unknown. 'Either 2+2=4 or Lot's wife was left-handed' sounds true to me. Odd.
4. Formal Logic / F. Set Theory ST / 1. Set Theory
To prove the consistency of set theory, we must go beyond set theory [Halbach]
     Full Idea: The consistency of set theory cannot be established without assumptions transcending set theory.
     From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 2.1)
Every attempt at formal rigour uses some set theory [Halbach]
     Full Idea: Almost any subject with any formal rigour employs some set theory.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 4.1)
     A reaction: This is partly because mathematics is often seen as founded in set theory, and formal rigour tends to be mathematical in character.
5. Theory of Logic / A. Overview of Logic / 6. Classical Logic
The underestimated costs of giving up classical logic are found in mathematical reasoning [Halbach]
     Full Idea: The costs of giving up classical logic are easily underestimated, …the price being paid in terms of mathematical reasoning.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 16.2)
     A reaction: No one cares much about such costs, until you say they are 'mathematical'. Presumably this is a message to Graham Priest and his pals.
5. Theory of Logic / C. Ontology of Logic / 1. Ontology of Logic
We can use truth instead of ontologically loaded second-order comprehension assumptions about properties [Halbach]
     Full Idea: The reduction of 2nd-order theories (of properties or sets) to axiomatic theories of truth may be conceived as a form of reductive nominalism, replacing existence assumptions (for comprehension axioms) by ontologically innocent truth assumptions.
     From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1.1)
     A reaction: I like this very much, as weeding properties out of logic (without weeding them out of the world). So-called properties in logic are too abundant, so there is a misfit with their role in science.
5. Theory of Logic / E. Structures of Logic / 7. Predicates in Logic
Instead of saying x has a property, we can say a formula is true of x - as long as we have 'true' [Halbach]
     Full Idea: Quantification over (certain) properties can be mimicked in a language with a truth predicate by quantifying over formulas. Instead of saying that Tom has the property of being a poor philosopher, we can say 'x is a poor philosopher' is true of Tom.
     From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1.1)
     A reaction: I love this, and think it is very important. He talks of 'mimicking' properties, but I see it as philosophers mistakenly attributing properties, when actually what they were doing is asserting truths involving certain predicates.
5. Theory of Logic / E. Structures of Logic / 8. Theories in Logic
A theory is some formulae and all of their consequences [Halbach]
     Full Idea: A theory is a set of formulae closed under first-order logical consequence.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 5.1)
5. Theory of Logic / K. Features of Logics / 3. Soundness
You cannot just say all of Peano arithmetic is true, as 'true' isn't part of the system [Halbach]
     Full Idea: One cannot just accept that all the theorems of Peano arithmetic are true when one accepts Peano arithmetic as the notion of truth is not available in the language of arithmetic.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 22.1)
     A reaction: This is given as the reason why Kreisel and Levy (1968) introduced 'reflection principles', which allow you to assert whatever has been proved (with no mention of truth). (I think. The waters are closing over my head).
Normally we only endorse a theory if we believe it to be sound [Halbach]
     Full Idea: If one endorses a theory, so one might argue, one should also take it to be sound.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 22.1)
Soundness must involve truth; the soundness of PA certainly needs it [Halbach]
     Full Idea: Soundness seems to be a notion essentially involving truth. At least I do not know how to fully express the soundness of Peano arithmetic without invoking a truth predicate.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 22.1)
     A reaction: I suppose you could use some alternative locution such as 'assertible' or 'cuddly'. Intuitionists seem a bit vague about the truth end of things.
5. Theory of Logic / L. Paradox / 1. Paradox
Many new paradoxes may await us when we study interactions between frameworks [Halbach]
     Full Idea: Paradoxes that arise from interaction of predicates such as truth, necessity, knowledge, future and past truths have receive little attention. There may be many unknown paradoxes lurking when we develop frameworks with these intensional notions.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 24.2)
     A reaction: Nice. This is a wonderful pointer to new research in the analytic tradition, in which formal problems will gradually iron out our metaphysical framework.
5. Theory of Logic / L. Paradox / 6. Paradoxes in Language / a. The Liar paradox
The liar paradox applies truth to a negated truth (but the conditional will serve equally) [Halbach]
     Full Idea: An essential feature of the liar paradox is the application of the truth predicate to a sentence with a negated occurrence of the truth predicate, though the negation can be avoided by using the conditional.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 19.3)
6. Mathematics / B. Foundations for Mathematics / 4. Axioms for Number / d. Peano arithmetic
The compactness theorem can prove nonstandard models of PA [Halbach]
     Full Idea: Nonstandard models of Peano arithmetic are models of PA that are not isomorphic to the standard model. Their existence can be established with the compactness theorem or the adequacy theorem of first-order logic.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 8.3)
The global reflection principle seems to express the soundness of Peano Arithmetic [Halbach]
     Full Idea: The global reflection principle ∀x(Sent(x) ∧ Bew[PA](x) → Tx) …seems to be the full statement of the soundness claim for Peano arithmetic, as it expresses that all theorems of Peano arithmetic are true.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 22.1)
     A reaction: That is, an extra principle must be introduced to express the soundness. PA is, of course, not complete.
6. Mathematics / B. Foundations for Mathematics / 6. Mathematics as Set Theory / a. Mathematics is set theory
To reduce PA to ZF, we represent the non-negative integers with von Neumann ordinals [Halbach]
     Full Idea: For the reduction of Peano Arithmetic to ZF set theory, usually the set of finite von Neumann ordinals is used to represent the non-negative integers.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 6)
     A reaction: Halbach makes it clear that this is just one mode of reduction, relative interpretability.
6. Mathematics / C. Sources of Mathematics / 6. Logicism / b. Type theory
Set theory was liberated early from types, and recent truth-theories are exploring type-free [Halbach]
     Full Idea: While set theory was liberated much earlier from type restrictions, interest in type-free theories of truth only developed more recently.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 4)
     A reaction: Tarski's theory of truth involves types (or hierarchies).
7. Existence / C. Structure of Existence / 2. Reduction
That Peano arithmetic is interpretable in ZF set theory is taken by philosophers as a reduction [Halbach]
     Full Idea: The observation that Peano arithmetic is relatively interpretable in ZF set theory is taken by many philosophers to be a reduction of numbers to sets.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 23)
     A reaction: Nice! Being able to express something in a different language is not the same as a reduction. Back to the drawing board. What do you really mean by a reduction? If we model something, we don't 'reduce' it to the model.
7. Existence / E. Categories / 2. Categorisation
Even fairly simple animals make judgements based on categories [Gelman]
     Full Idea: All organisms form categories: even mealworms have category-based preferences, and higher-order animals such as pigeons or octopi can display quite sophisticated categorical judgements.
     From: Susan A. Gelman (The Essential Child [2003], 01 'Prelims')
     A reaction: [She cites some 1980 research to support this] This comes as no surprise, as I take categorisation as almost definitive of what a mind is. My surmise is that some sort of 'labelling' system is at the heart of it (like Googlemail labels!).
Children accept real stable categories, with nonobvious potential that gives causal explanations [Gelman]
     Full Idea: By five children assume that a variety of categories have rich inductive potential, are stable over outward transformations, include crucial nonobvious properties, have innate potential, privilege causal features, can be explained causally, and are real.
     From: Susan A. Gelman (The Essential Child [2003], 06 'Intro')
     A reaction: This is Gelman's helpful summary of the findings of research on childhood essentialising, and says the case for this phenomenon is 'compelling'.
9. Objects / D. Essence of Objects / 1. Essences of Objects
In India, upper-castes essentialize caste more than lower-castes do [Gelman]
     Full Idea: The notion of caste in India is more essentialized among upper-caste than lower-caste individuals.
     From: Susan A. Gelman (The Essential Child [2003], 08 'Intro')
     A reaction: In a book defending fairly innate essentialism in the human race, Gelman offers this point as a warning that large cultural ingredients can be involved. Racism is the classic difficulty with essentialism.
Essentialism is either natural to us, or an accident of our culture, or a necessary result of language [Gelman]
     Full Idea: The two views contrasting with essentialism naturally emerging in childhood are the claim that essentialism is a historical accident emerging from Western philosophy, and that essentialism is an inherent consequence of naming things.
     From: Susan A. Gelman (The Essential Child [2003], 01 'Background')
     A reaction: Helpful. I take Idea 15682 to rule out the idea that it is just a feature of western culture. I can't conceive of early man surviving without essentialism. I don't think it rules out the naming view. Animals may do what emerges in us as full 'naming'.
Children's concepts include nonobvious features, like internal parts, functions and causes [Gelman]
     Full Idea: Children incorporate a variety of nonobvious features into their concepts, including internal parts, functions, causes, and ontological distinctions.
     From: Susan A. Gelman (The Essential Child [2003], 01 'Prelims')
     A reaction: This remark sums up the general thesis of her book, which she supports with a wealth of first-hand evidence. It supports my view, that the desire and need for explanation is at the root of essentialist concepts. It's hard wired in us.
9. Objects / D. Essence of Objects / 2. Types of Essence
Essentialism: real or representational? sortal, causal or ideal? real particulars, or placeholders? [Gelman]
     Full Idea: We map types of essentialism by asking is it in the world or in our representations, is it sortal or causal or ideal, and is it specific particulars or placeholders for the unknown?
     From: Susan A. Gelman (The Essential Child [2003], 01 'Prelims')
     A reaction: I am struck by the way that this practising experimental psychologist gets to ask questions and make distinctions much more extensively than most armchair philosophers on the subject. She focuses on the representational, causal, placeholder view.
9. Objects / D. Essence of Objects / 5. Essence as Kind
Essentialism says categories have a true hidden nature which gives an object its identity [Gelman]
     Full Idea: Essentialism is the view that categories have an underlying reality or true nature that one cannot observe directly but that gives an object its identity.
     From: Susan A. Gelman (The Essential Child [2003], 01 'Intro')
     A reaction: I think the introduction of categories here is a misunderstanding. Does an uncategorisable thing therefore have no identity (even though it has properties)? If categories give objects their identity, what gives categories their identity?
Sortals are needed for determining essence - the thing must be categorised first [Gelman]
     Full Idea: I suggest that sortals are likewise required for determining essence. One cannot answer the question 'What is the essence of this?' without supplying the sortal - of this 'what'.
     From: Susan A. Gelman (The Essential Child [2003], 01 'Prelims')
     A reaction: I remain baffled by this view. I take the category to be an inductive generalisation from other similar individuals. It can't get off the ground if you don't start with the individuals. Sortals are just a shorthand.
Kind (unlike individual) essentialism assumes preexisting natural categories [Gelman]
     Full Idea: With kind essentialism the person assumes that the world is divided up into preexisting natural categories. Individual essentialism seems not to require any such commitment to kind realism.
     From: Susan A. Gelman (The Essential Child [2003], 06 'Essentialism')
     A reaction: This pinpoints my difficulty: how do we decide whether some category or attributed essence is part of a preexisting natural kind? Some natural kinds are self-evident, like water (roughly), but others need subtle teasing out. How is the teasing done?
9. Objects / D. Essence of Objects / 7. Essence and Necessity / c. Essentials are necessary
Kinship is essence that comes in degrees, and age groups are essences that change over time [Gelman]
     Full Idea: Kinship is essentialized, but admits of degrees, ...and people can be essentialist even about categories they do not view as fixed over time, such as age groupings.
     From: Susan A. Gelman (The Essential Child [2003], 03 'Summary')
     A reaction: Given my notion of essence are necessarily explanatory, I embrace both of these points. Being very athletic comes in degrees, and changes over times.
9. Objects / D. Essence of Objects / 14. Knowledge of Essences
Essentialism comes from the cognitive need to categorise [Gelman]
     Full Idea: Essentialism has its source in the cognitive requirement of categorization in certain domains - particularly as they affect the young learner.
     From: Susan A. Gelman (The Essential Child [2003], 01 'Essentialist')
     A reaction: I think the phenomenon is better understood as part of the cognitive requirement to understand and explain. Categorisation is just one way to aid explanation. Children try to understand (essentially) a new animal without categorisation.
We found no evidence that mothers teach essentialism to their children [Gelman]
     Full Idea: We found no evidence that mothers teach essentialism to their children. ...Mothers teach children about kinds, not about essences, and mothers help children identify which categories are richly structured.
     From: Susan A. Gelman (The Essential Child [2003], 07 'Conclusions')
     A reaction: This is a psychologist who specialises in this topic. If you think essentialism is inculcated by a our culture, you will have to blame the fathers.
9. Objects / D. Essence of Objects / 15. Against Essentialism
Essentialism is useful for predictions, but it is not the actual structure of reality [Gelman]
     Full Idea: Essentialism is a reasoning heuristic that allows us to make fairly good predictions much of the time, but it should not be confused with the structure of reality.
     From: Susan A. Gelman (The Essential Child [2003], 11 'Discussion')
     A reaction: She particularly cites biology as the area where it might be inaccurate. I'm beginning to think that the operations of induction are the place to look for an good understanding of essentialism.
9. Objects / E. Objects over Time / 12. Origin as Essential
Peope favor historical paths over outward properties when determining what something is [Gelman]
     Full Idea: People favor historical paths over outward properties when determining what something is. ...An object looking like a knife is less likely to be called 'a knife' if it is described as having been created by accident.
     From: Susan A. Gelman (The Essential Child [2003], 06 'Essentialism')
     A reaction: I like this because it talks, suggestively, of 'historical paths' rather than of 'origin'. Thus we might judge a person's identity by their traumatic experience rather than by their birth. This doesn't challenge necessity of origin, but affects labels.
10. Modality / A. Necessity / 2. Nature of Necessity
Maybe necessity is a predicate, not the usual operator, to make it more like truth [Halbach]
     Full Idea: Should necessity be treated as a predicate rather than (as in modal logic) as a sentential operator? It is odd to assign different status to necessity and truth, hampering their interaction. That all necessities are true can't be expressed by an operator.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 24.2)
     A reaction: [compressed] Halbach and Horsten consistently treat truth as a predicate, but maybe truth is an operator. Making necessity a predicate and not an operator would be a huge upheaval in the world of modal logic. Nice move!
11. Knowledge Aims / A. Knowledge / 2. Understanding
There is intentional, mechanical, teleological, essentialist, vitalist and deontological understanding [Gelman]
     Full Idea: The modes of understanding (or modes of construal) which have been proposed are intentional, mechanical, teleological, essentialist, vitalist (perhaps), and deontological.
     From: Susan A. Gelman (The Essential Child [2003], 11 'Broadening')
     A reaction: She cites psychological research to support this, and calls it 'a relatively small number' of modes. Compare Aristotle's four modes of cause/explanation.
12. Knowledge Sources / B. Perception / 4. Sense Data / d. Sense-data problems
We are not conscious of pure liquidity, but of the liquidity of water [Firth]
     Full Idea: We are not conscious of liquidity, coldness, and solidity, but of the liquidity of water, the coldness of ice, and the solidity of rocks.
     From: Roderick Firth (Sense Data and the Percept Theory [1949]), quoted by Howard Robinson - Perception 1.7
     A reaction: A nice point, but it might not be entirely true in a blindfold test, where one might only report properties like 'sticky' or 'warm', without having any clear concept of the substance being experienced. Firth is proposing the 'percept theory'.
12. Knowledge Sources / E. Direct Knowledge / 4. Memory
Memories often conform to a theory, rather than being neutral [Gelman]
     Full Idea: Memory is notorious for conforming to theory (rather than memory being a neutral source of information).
     From: Susan A. Gelman (The Essential Child [2003], 09 'Theory')
     A reaction: This observation by a psychologist is music to sceptics about objectivity. Memory is so fundamental to our basic epistemology that it could even be the nature of thought itself.
14. Science / C. Induction / 1. Induction
Inductive success is rewarded with more induction [Gelman]
     Full Idea: Inductive success is rewarded with more induction.
     From: Susan A. Gelman (The Essential Child [2003], 11 'Broadening')
     A reaction: I love this one. Neat, accurate, and central to how we understand the world. I take inductive success to be stored as labels, concepts, categories, words and general truths, which are then our resource for further attempts.
14. Science / C. Induction / 3. Limits of Induction
Children overestimate the power of a single example [Gelman]
     Full Idea: We suggest that children overestimate the power of a single example.
     From: Susan A. Gelman (The Essential Child [2003], 06 'The role')
     A reaction: This conclusion arises from extensive psychological research. 'My grandma smoked, and she lived to be 97' - adults do this too. Wittgenstein says assuming other minds because of your own is induction from one example!
Children make errors in induction by focusing too much on categories [Gelman]
     Full Idea: Because of their narrow focus, children's sensitivity to categories as the basis of induction is a reasoning bias that, though useful much of the time, results in systematic errors.
     From: Susan A. Gelman (The Essential Child [2003], 06 'The role')
     A reaction: This is the bad sense of 'essentialism' which worries its opponents. Presumably, though, my favoured scientific essentialism will be 'scientific', and avoid this problem. The relation between categories and induction needs to be clear.
14. Science / D. Explanation / 1. Explanation / a. Explanation
People tend to be satisfied with shallow explanations [Gelman]
     Full Idea: People tend to be satisfied with rather shallow explanations.
     From: Susan A. Gelman (The Essential Child [2003], 06 'Is essentialism')
     A reaction: She cites some psychological research to support this. Pretty obvious really. I take the so-called 'scientific method' to be nothing more than ceasing to be satisfied with such shallowness.
18. Thought / A. Modes of Thought / 4. Folk Psychology
Folk essentialism rests on belief in natural kinds, in hidden properties, and on words indicating structures [Gelman]
     Full Idea: The three components of essentialism as a folk belief are the idea that certain categories are natural kinds, the idea that some unobservable property causes the way things are, and the idea that words reflect real structures.
     From: Susan A. Gelman (The Essential Child [2003], 01 'Prelims')
18. Thought / D. Concepts / 3. Ontology of Concepts / a. Concepts as representations
Labels may indicate categories which embody an essence [Gelman]
     Full Idea: Labels may signal categories that are believed to embody an essence.
     From: Susan A. Gelman (The Essential Child [2003], 02 'Privileged')
     A reaction: This is quoted by her, as a summary of a substantial body of research which she endorses. I cite it because it pinpoints my own view. I take 'labels' to be basic to minds, as organisers of thought, and this ties essences to labels. Satisfying picture.
18. Thought / D. Concepts / 4. Structure of Concepts / a. Conceptual structure
Causal properties are seen as more central to category concepts [Gelman]
     Full Idea: Properties that enter into causally meaningful links are better remembered and are treated as more central to the category than properties that are not causally meaningful.
     From: Susan A. Gelman (The Essential Child [2003], 05 'Causation2')
     A reaction: This is a summary of considerable psychological research. This account not only sounds plausible, but would fit better withy why we form concepts and categories in the first place. We are trying to relate to the causations of nature.
18. Thought / D. Concepts / 4. Structure of Concepts / d. Concepts as prototypes
Categories are characterized by distance from a prototype [Gelman]
     Full Idea: On prototype views, categories are characterized by distance from a prototype.
     From: Susan A. Gelman (The Essential Child [2003], 05 'Causation')
     A reaction: Gelman observes that this view makes no reference to any causal features of things. This cuts them off from using underlying essences in the process of categorisation and concept-formation. How do you spot a prototype, with no category?
18. Thought / D. Concepts / 4. Structure of Concepts / f. Theory theory of concepts
Theory-based concepts use rich models to show which similarities really matter [Gelman]
     Full Idea: Theory-based approaches to categories are a response to the limitations of mere similarities holding the category together, and require knowledge-rich explanatory models to say which features are more central to a concept.
     From: Susan A. Gelman (The Essential Child [2003], 05 'Causation1')
     A reaction: I see a promising account in linking theory theory to essentialism. For a physical object (or even for a process) infer a structure, and then identify what is most important in that structure. That gives you your stable, agreed concept.
18. Thought / D. Concepts / 5. Concepts and Language / c. Concepts without language
Prelinguistic infants acquire and use many categories [Gelman]
     Full Idea: Language does not appear to be necessary for forming categories, since prelinguistic infants acquire many categories, and even use categories to form inferences about unknown properties.
     From: Susan A. Gelman (The Essential Child [2003], 08 'Intro')
     A reaction: She cites lots of research in support of this claim. The idea may come as a surprise to some people, but not to me. I take it that categorisation is what a brain is for, including animal brains.
19. Language / D. Propositions / 4. Mental Propositions
We need propositions to ascribe the same beliefs to people with different languages [Halbach]
     Full Idea: Being able to ascribe the same proposition as a belief to persons who do not have a common language seems to be one of the main reasons to employ propositions.
     From: Volker Halbach (Axiomatic Theories of Truth [2011], 2)
     A reaction: Propositions concern beliefs, as well as sentence meanings. I would want to say that a dog and I could believe the same thing, and that is a non-linguistic reason to believe in propositions. Maybe 'translation' cuts out the proposition middleman?
26. Natural Theory / B. Natural Kinds / 3. Knowing Kinds
One sample of gold is enough, but one tree doesn't give the height of trees [Gelman]
     Full Idea: We can confidently determine the chemical composition of gold from just a single sample, but we cannot determine the height of trees from just a single tree.
     From: Susan A. Gelman (The Essential Child [2003], 06 'The role')
     A reaction: The tricky word here is 'confidently'. If you meet one Latvian who is nice, do you assume they are all nice? At what point do you decide gold etc. really are natural kinds, where one sample tells all? Evolution of species...
26. Natural Theory / B. Natural Kinds / 5. Reference to Natural Kinds
Nouns seem to invoke stable kinds more than predicates do [Gelman]
     Full Idea: Children judged personal characteristics as more stable when they were referred to by a noun ('She is a carrot eater') than by a verbal predicate ('She eats carrots whenever she can')
     From: Susan A. Gelman (The Essential Child [2003], 08 'Naming')
     A reaction: This fits with my feeling that 'labels' are the basis of how the mind works. The noun invokes a genuine category of thing, where a predicate attaches to some preselected category ('she'). Gelman says names encourage inductions.
26. Natural Theory / D. Laws of Nature / 8. Scientific Essentialism / a. Scientific essentialism
Essentialism encourages us to think about the world scientifically [Gelman]
     Full Idea: Essentialism encourages a 'scientific' mindset in thinking about the natural world, a belief that intensive study of a natural domain will yield ever more underlying properties.
     From: Susan A. Gelman (The Essential Child [2003], 11 'Intro')
     A reaction: Maybe scientists must be committed to essences, the way mathematicians must be committed to numbers? This idea spendidly opposes the doubts expressed by Popper.
Essentialism doesn't mean we know the essences [Gelman]
     Full Idea: Essentialism does not entail that people know what the essence is.
     From: Susan A. Gelman (The Essential Child [2003], 09 'Theory')
     A reaction: This is a fundamental and (I would say) fairly obvious point, but it needs to be made to the more passionate opponents of essentialism.
26. Natural Theory / D. Laws of Nature / 8. Scientific Essentialism / d. Knowing essences
Essentialism starts from richly structured categories, leading to a search for underlying properties [Gelman]
     Full Idea: If my speculations are correct, then essentialism starts out strictly as a belief that many categories are richly structured kinds, then additionally becomes a search for underlying inherent properties.
     From: Susan A. Gelman (The Essential Child [2003], 10 'Figuring')
     A reaction: This is her summary of extensive essentialist research among children. She favours the priority of kinds and categories. We actually change taxonomies on the basis of revisions in our accounts of essence. Science negotiates.
26. Natural Theory / D. Laws of Nature / 8. Scientific Essentialism / e. Anti scientific essentialism
A major objection to real essences is the essentialising of social categories like race, caste and occupation [Gelman]
     Full Idea: One major argument against the view that essences are real is the rampant essentializing of categories that are socially constructed (such as race, caste and occupation).
     From: Susan A. Gelman (The Essential Child [2003], 11 'Is essentialism')
     A reaction: You can't argue with that. It raises the question of whether the approach of scientific essentialism has any value in the social, rather than physical, sciences. We jokingly essentialise groups of people such as referees or Oxonians.