Combining Texts

All the ideas for 'Content Preservation', 'On Liberty' and 'Introducing the Philosophy of Mathematics'

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67 ideas

2. Reason / D. Definition / 8. Impredicative Definition
An 'impredicative' definition seems circular, because it uses the term being defined [Friend]
     Full Idea: An 'impredicative' definition is one that uses the terms being defined in order to give the definition; in some way the definition is then circular.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], Glossary)
     A reaction: There has been a big controversy in the philosophy of mathematics over these. Shapiro gives the definition of 'village idiot' (which probably mentions 'village') as an example.
2. Reason / D. Definition / 10. Stipulative Definition
Classical definitions attempt to refer, but intuitionist/constructivist definitions actually create objects [Friend]
     Full Idea: In classical logic definitions are thought of as revealing our attempts to refer to objects, ...but for intuitionist or constructivist logics, if our definitions do not uniquely characterize an object, we are not entitled to discuss the object.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.4)
     A reaction: In defining a chess piece we are obviously creating. In defining a 'tree' we are trying to respond to fact, but the borderlines are vague. Philosophical life would be easier if we were allowed a mixture of creation and fact - so let's have that.
2. Reason / E. Argument / 5. Reductio ad Absurdum
Reductio ad absurdum proves an idea by showing that its denial produces contradiction [Friend]
     Full Idea: Reductio ad absurdum arguments are ones that start by denying what one wants to prove. We then prove a contradiction from this 'denied' idea and more reasonable ideas in one's theory, showing that we were wrong in denying what we wanted to prove.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.3)
     A reaction: This is a mathematical definition, which rests on logical contradiction, but in ordinary life (and philosophy) it would be enough to show that denial led to absurdity, rather than actual contradiction.
3. Truth / A. Truth Problems / 8. Subjective Truth
Anti-realists see truth as our servant, and epistemically contrained [Friend]
     Full Idea: For the anti-realist, truth belongs to us, it is our servant, and as such, it must be 'epistemically constrained'.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 5.1)
     A reaction: Put as clearly as this, it strikes me as being utterly and spectacularly wrong, a complete failure to grasp the elementary meaning of a concept etc. etc. If we aren't the servants of truth then we jolly we ought to be. Truth is above us.
4. Formal Logic / B. Propositional Logic PL / 3. Truth Tables
In classical/realist logic the connectives are defined by truth-tables [Friend]
     Full Idea: In the classical or realist view of logic the meaning of abstract symbols for logical connectives is given by the truth-tables for the symbol.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007])
     A reaction: Presumably this is realist because it connects them to 'truth', but only if that involves a fairly 'realist' view of truth. You could, of course, translate 'true' and 'false' in the table to empty (formalist) symbols such a 0 and 1. Logic is electronics.
4. Formal Logic / E. Nonclassical Logics / 2. Intuitionist Logic
Double negation elimination is not valid in intuitionist logic [Friend]
     Full Idea: In intuitionist logic, if we do not know that we do not know A, it does not follow that we know A, so the inference (and, in general, double negation elimination) is not intuitionistically valid.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 5.2)
     A reaction: That inference had better not be valid in any logic! I am unaware of not knowing the birthday of someone I have never heard of. Propositional attitudes such as 'know' are notoriously difficult to explain in formal logic.
4. Formal Logic / E. Nonclassical Logics / 6. Free Logic
Free logic was developed for fictional or non-existent objects [Friend]
     Full Idea: Free logic is especially designed to help regiment our reasoning about fictional objects, or nonexistent objects of some sort.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 3.7)
     A reaction: This makes it sound marginal, but I wonder whether existential commitment shouldn't be eliminated from all logic. Why do fictional objects need a different logic? What logic should we use for Robin Hood, if we aren't sure whether or not he is real?
4. Formal Logic / F. Set Theory ST / 2. Mechanics of Set Theory / b. Terminology of ST
A 'proper subset' of A contains only members of A, but not all of them [Friend]
     Full Idea: A 'subset' of A is a set containing only members of A, and a 'proper subset' is one that does not contain all the members of A. Note that the empty set is a subset of every set, but it is not a member of every set.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.5)
     A reaction: Is it the same empty set in each case? 'No pens' is a subset of 'pens', but is it a subset of 'paper'? Idea 8219 should be borne in mind when discussing such things, though I am not saying I agree with it.
A 'powerset' is all the subsets of a set [Friend]
     Full Idea: The 'powerset' of a set is a set made up of all the subsets of a set. For example, the powerset of {3,7,9} is {null, {3}, {7}, {9}, {3,7}, {3,9}, {7,9}, {3,7,9}}. Taking the powerset of an infinite set gets us from one infinite cardinality to the next.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.5)
     A reaction: Note that the null (empty) set occurs once, but not in the combinations. I begin to have queasy sympathies with the constructivist view of mathematics at this point, since no one has the time, space or energy to 'take' an infinite powerset.
4. Formal Logic / F. Set Theory ST / 3. Types of Set / b. Empty (Null) Set
Set theory makes a minimum ontological claim, that the empty set exists [Friend]
     Full Idea: As a realist choice of what is basic in mathematics, set theory is rather clever, because it only makes a very simple ontological claim: that, independent of us, there exists the empty set. The whole hierarchy of finite and infinite sets then follows.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.3)
     A reaction: Even so, for non-logicians the existence of the empty set is rather counterintuitive. "There was nobody on the road, so I overtook him". See Ideas 7035 and 8322. You might work back to the empty set, but how do you start from it?
4. Formal Logic / F. Set Theory ST / 3. Types of Set / d. Infinite Sets
Infinite sets correspond one-to-one with a subset [Friend]
     Full Idea: Two sets are the same size if they can be placed in one-to-one correspondence. But even numbers have one-to-one correspondence with the natural numbers. So a set is infinite if it has one-one correspondence with a proper subset.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.5)
     A reaction: Dedekind's definition. We can match 1 with 2, 2 with 4, 3 with 6, 4 with 8, etc. Logicians seem happy to give as a definition anything which fixes the target uniquely, even if it doesn't give the essence. See Frege on 0 and 1, Ideas 8653/4.
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / a. Axioms for sets
Major set theories differ in their axioms, and also over the additional axioms of choice and infinity [Friend]
     Full Idea: Zermelo-Fraenkel and Gödel-Bernays set theory differ over the notions of ordinal construction and over the notion of class, among other things. Then there are optional axioms which can be attached, such as the axiom of choice and the axiom of infinity.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.6)
     A reaction: This summarises the reasons why we cannot just talk about 'set theory' as if it was a single concept. The philosophical interest I would take to be found in disentangling the ontological commitments of each version.
5. Theory of Logic / D. Assumptions for Logic / 2. Excluded Middle
The law of excluded middle is syntactic; it just says A or not-A, not whether they are true or false [Friend]
     Full Idea: The law of excluded middle is purely syntactic: it says for any well-formed formula A, either A or not-A. It is not a semantic law; it does not say that either A is true or A is false. The semantic version (true or false) is the law of bivalence.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 5.2)
     A reaction: No wonder these two are confusing, sufficiently so for a lot of professional philosophers to blur the distinction. Presumably the 'or' is exclusive. So A-and-not-A is a contradiction; but how do you explain a contradiction without mentioning truth?
5. Theory of Logic / G. Quantification / 7. Unorthodox Quantification
Intuitionists read the universal quantifier as "we have a procedure for checking every..." [Friend]
     Full Idea: In the intuitionist version of quantification, the universal quantifier (normally read as "all") is understood as "we have a procedure for checking every" or "we have checked every".
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 5.5)
     A reaction: It seems better to describe this as 'verificationist' (or, as Dummett prefers, 'justificationist'). Intuition suggests an ability to 'see' beyond the evidence. It strikes me as bizarre to say that you can't discuss things you can't check.
5. Theory of Logic / L. Paradox / 5. Paradoxes in Set Theory / a. Set theory paradoxes
Paradoxes can be solved by talking more loosely of 'classes' instead of 'sets' [Friend]
     Full Idea: The realist meets the Burali-Forti paradox by saying that all the ordinals are a 'class', not a set. A proper class is what we discuss when we say "all" the so-and-sos when they cannot be reached by normal set-construction. Grammar is their only limit.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.3)
     A reaction: This strategy would be useful for Class Nominalism, which tries to define properties in terms of classes, but gets tangled in paradoxes. But why bother with strict sets if easy-going classes will do just as well? Descartes's Dream: everything is rational.
5. Theory of Logic / L. Paradox / 5. Paradoxes in Set Theory / c. Burali-Forti's paradox
The Burali-Forti paradox asks whether the set of all ordinals is itself an ordinal [Friend]
     Full Idea: The Burali-Forti paradox says that if ordinals are defined by 'gathering' all their predecessors with the empty set, then is the set of all ordinals an ordinal? It is created the same way, so it should be a further member of this 'complete' set!
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.3)
     A reaction: This is an example (along with Russell's more famous paradox) of the problems that began to appear in set theory in the early twentieth century. See Idea 8675 for a modern solution.
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / b. Types of number
The 'integers' are the positive and negative natural numbers, plus zero [Friend]
     Full Idea: The set of 'integers' is all of the negative natural numbers, and zero, together with the positive natural numbers.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.5)
     A reaction: Zero always looks like a misfit at this party. Credit and debit explain positive and negative nicely, but what is the difference between having no money, and money being irrelevant? I can be 'broke', but can the North Pole be broke?
The 'rational' numbers are those representable as fractions [Friend]
     Full Idea: The 'rational' numbers are all those that can be represented in the form m/n (i.e. as fractions), where m and n are natural numbers different from zero.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.5)
     A reaction: Pythagoreans needed numbers to stop there, in order to represent the whole of reality numerically. See irrational numbers for the ensuing disaster. How can a universe with a finite number of particles contain numbers that are not 'rational'?
A number is 'irrational' if it cannot be represented as a fraction [Friend]
     Full Idea: A number is 'irrational' just in case it cannot be represented as a fraction. An irrational number has an infinite non-repeating decimal expansion. Famous examples are pi and e.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.5)
     A reaction: There must be an infinite number of irrational numbers. You could, for example, take the expansion of pi, and change just one digit to produce a new irrational number, and pi has an infinity of digits to tinker with.
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / c. Priority of numbers
The natural numbers are primitive, and the ordinals are up one level of abstraction [Friend]
     Full Idea: The natural numbers are quite primitive, and are what we first learn about. The order of objects (the 'ordinals') is one level of abstraction up from the natural numbers: we impose an order on objects.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.4)
     A reaction: Note the talk of 'levels of abstraction'. So is there a first level of abstraction? Dedekind disagrees with Friend (Idea 7524). I would say that natural numbers are abstracted from something, but I'm not sure what. See Structuralism in maths.
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / f. Cardinal numbers
Cardinal numbers answer 'how many?', with the order being irrelevant [Friend]
     Full Idea: The 'cardinal' numbers answer the question 'How many?'; the order of presentation of the objects being counted as immaterial. Def: the cardinality of a set is the number of members of the set.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.5)
     A reaction: If one asks whether cardinals or ordinals are logically prior (see Ideas 7524 and 8661), I am inclined to answer 'neither'. Presenting them as answers to the questions 'how many?' and 'which comes first?' is illuminating.
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / g. Real numbers
The 'real' numbers (rationals and irrationals combined) is the Continuum, which has no gaps [Friend]
     Full Idea: The set of 'real' numbers, which consists of the rational numbers and the irrational numbers together, represents "the continuum", since it is like a smooth line which has no gaps (unlike the rational numbers, which have the irrationals missing).
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.5)
     A reaction: The Continuum is the perfect abstract object, because a series of abstractions has arrived at a vast limit in its nature. It still has dizzying infinities contained within it, and at either end of the line. It makes you feel humble.
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / h. Ordinal infinity
Raising omega to successive powers of omega reveal an infinity of infinities [Friend]
     Full Idea: After the multiples of omega, we can successively raise omega to powers of omega, and after that is done an infinite number of times we arrive at a new limit ordinal, which is called 'epsilon'. We have an infinite number of infinite ordinals.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.4)
     A reaction: When most people are dumbstruck by the idea of a single infinity, Cantor unleashes an infinity of infinities, which must be the highest into the stratosphere of abstract thought that any human being has ever gone.
The first limit ordinal is omega (greater, but without predecessor), and the second is twice-omega [Friend]
     Full Idea: The first 'limit ordinal' is called 'omega', which is ordinal because it is greater than other numbers, but it has no immediate predecessor. But it has successors, and after all of those we come to twice-omega, which is the next limit ordinal.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.4)
     A reaction: This is the gateway to Cantor's paradise of infinities, which Hilbert loved and defended. Who could resist the pleasure of being totally boggled (like Aristotle) by a concept such as infinity, only to have someone draw a map of it? See 8663 for sequel.
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / j. Infinite divisibility
Between any two rational numbers there is an infinite number of rational numbers [Friend]
     Full Idea: Since between any two rational numbers there is an infinite number of rational numbers, we could consider that we have infinity in three dimensions: positive numbers, negative numbers, and the 'depth' of infinite numbers between any rational numbers.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 1.5)
     A reaction: This is before we even reach Cantor's staggering infinities (Ideas 8662 and 8663), which presumably reside at the outer reaches of all three of these dimensions of infinity. The 'deep' infinities come from fractions with huge denominators.
6. Mathematics / B. Foundations for Mathematics / 1. Foundations for Mathematics
Is mathematics based on sets, types, categories, models or topology? [Friend]
     Full Idea: Successful competing founding disciplines in mathematics include: the various set theories, type theory, category theory, model theory and topology.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.3)
     A reaction: Or none of the above? Set theories are very popular. Type theory is, apparently, discredited. Shapiro has a version of structuralism based on model theory (which sound promising). Topology is the one that intrigues me...
6. Mathematics / B. Foundations for Mathematics / 6. Mathematics as Set Theory / a. Mathematics is set theory
Most mathematical theories can be translated into the language of set theory [Friend]
     Full Idea: Most of mathematics can be faithfully redescribed by classical (realist) set theory. More precisely, we can translate other mathematical theories - such as group theory, analysis, calculus, arithmetic, geometry and so on - into the language of set theory.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.3)
     A reaction: This is why most mathematicians seem to regard set theory as foundational. We could also translate football matches into the language of atomic physics.
6. Mathematics / B. Foundations for Mathematics / 7. Mathematical Structuralism / a. Structuralism
The number 8 in isolation from the other numbers is of no interest [Friend]
     Full Idea: There is no interest for the mathematician in studying the number 8 in isolation from the other numbers.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 4.4)
     A reaction: This is a crucial and simple point (arising during a discussion of Shapiro's structuralism). Most things are interesting in themselves, as well as for their relationships, but mathematical 'objects' just are relationships.
In structuralism the number 8 is not quite the same in different structures, only equivalent [Friend]
     Full Idea: Structuralists give a historical account of why the 'same' number occupies different structures. Numbers are equivalent rather than identical. 8 is the immediate predecessor of 9 in the whole numbers, but in the rationals 9 has no predecessor.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 4.4)
     A reaction: I don't become a different person if I move from a detached house to a terraced house. This suggests that 8 can't be entirely defined by its relations, and yet it is hard to see what its intrinsic nature could be, apart from the units which compose it.
6. Mathematics / B. Foundations for Mathematics / 7. Mathematical Structuralism / b. Varieties of structuralism
Are structures 'ante rem' (before reality), or are they 'in re' (grounded in physics)? [Friend]
     Full Idea: Structuralists disagree over whether objects in structures are 'ante rem' (before reality, existing independently of whether the objects exist) or 'in re' (in reality, grounded in the real world, usually in our theories of physics).
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 4.4)
     A reaction: Shapiro holds the first view, Hellman and Resnik the second. The first view sounds too platonist and ontologically extravagant; the second sounds too contingent and limited. The correct account is somewhere in abstractions from the real.
6. Mathematics / B. Foundations for Mathematics / 7. Mathematical Structuralism / c. Nominalist structuralism
Structuralist says maths concerns concepts about base objects, not base objects themselves [Friend]
     Full Idea: According to the structuralist, mathematicians study the concepts (objects of study) such as variable, greater, real, add, similar, infinite set, which are one level of abstraction up from prima facie base objects such as numbers, shapes and lines.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 4.1)
     A reaction: This still seems to imply an ontology in which numbers, shapes and lines exist. I would have thought you could eliminate the 'base objects', and just say that the concepts are one level of abstraction up from the physical world.
Structuralism focuses on relations, predicates and functions, with objects being inessential [Friend]
     Full Idea: Structuralism says we study whole structures: objects together with their predicates, relations that bear between them, and functions that take us from one domain of objects to a range of other objects. The objects can even be eliminated.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 4.1)
     A reaction: The unity of object and predicate is a Quinean idea. The idea that objects are inessential is the dramatic move. To me the proposal has very strong intuitive appeal. 'Eight' is meaningless out of context. Ordinality precedes cardinality? Ideas 7524/8661.
6. Mathematics / B. Foundations for Mathematics / 7. Mathematical Structuralism / d. Platonist structuralism
'In re' structuralism says that the process of abstraction is pattern-spotting [Friend]
     Full Idea: In the 'in re' version of mathematical structuralism, pattern-spotting is the process of abstraction.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 4.4)
     A reaction: This might work for non-mathematical abstraction as well, if we are allowed to spot patterns within sensual experience, and patterns within abstractions. Properties are causal patterns in the world? No - properties cause patterns.
6. Mathematics / C. Sources of Mathematics / 1. Mathematical Platonism / b. Against mathematical platonism
The big problem for platonists is epistemic: how do we perceive, intuit, know or detect mathematical facts? [Friend]
     Full Idea: The main philosophical problem with the position of platonism or realism is the epistemic problem: of explaining what perception or intuition consists in; how it is possible that we should accurately detect whatever it is we are realists about.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.5)
     A reaction: The best bet, I suppose, is that the mind directly perceives concepts just as eyes perceive the physical (see Idea 8679), but it strikes me as implausible. If we have to come up with a special mental faculty for an area of knowledge, we are in trouble.
6. Mathematics / C. Sources of Mathematics / 4. Mathematical Empiricism / b. Indispensability of mathematics
Mathematics should be treated as true whenever it is indispensable to our best physical theory [Friend]
     Full Idea: Central to naturalism about mathematics are 'indispensability arguments', to the effect that some part of mathematics is indispensable to our best physical theory, and therefore we ought to take that part of mathematics to be true.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 6.1)
     A reaction: Quine and Putnam hold this view; Field challenges it. It has the odd consequence that the dispensable parts (if they can be identified!) do not need to be treated as true (even though they might follow logically from the dispensable parts!). Wrong!
6. Mathematics / C. Sources of Mathematics / 7. Formalism
Formalism is unconstrained, so cannot indicate importance, or directions for research [Friend]
     Full Idea: There are not enough constraints in the Formalist view of mathematics, so there is no way to select a direction for trying to develop mathematics. There is no part of mathematics that is more important than another.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 6.6)
     A reaction: One might reply that an area of maths could be 'important' if lots of other areas depended on it, and big developments would ripple big changes through the interior of the subject. Formalism does, though, seem to reduce maths to a game.
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / a. Constructivism
Constructivism rejects too much mathematics [Friend]
     Full Idea: Too much of mathematics is rejected by the constructivist.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 5.1)
     A reaction: This was Hilbert's view. This seems to be generally true of verificationism. My favourite example is that legitimate speculations can be labelled as meaningless.
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / b. Intuitionism
Intuitionists typically retain bivalence but reject the law of excluded middle [Friend]
     Full Idea: An intuitionist typically retains bivalence, but rejects the law of excluded middle.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 5.2)
     A reaction: The idea would be to say that only T and F are available as truth-values, but failing to be T does not ensure being F, but merely not-T. 'Unproven' is not-T, but may not be F.
9. Objects / A. Existence of Objects / 2. Abstract Objects / a. Nature of abstracta
Structuralists call a mathematical 'object' simply a 'place in a structure' [Friend]
     Full Idea: What the mathematician labels an 'object' in her discipline, is called 'a place in a structure' by the structuralist.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 4.5)
     A reaction: This is a strategy for dispersing the idea of an object in the world of thought, parallel to attempts to eliminate them from physical ontology (e.g. Idea 614).
13. Knowledge Criteria / C. External Justification / 1. External Justification
Subjects may be unaware of their epistemic 'entitlements', unlike their 'justifications' [Burge]
     Full Idea: I call 'entitlement' (as opposed to justification) the epistemic rights or warrants that need not be understood by or even be accessible to the subject.
     From: Tyler Burge (Content Preservation [1993]), quoted by Paul Boghossian - Analyticity Reconsidered §III
     A reaction: I espouse a coherentism that has both internal and external components, and is mediated socially. In Burge's sense, animals will sometimes have 'entitlement'. I prefer, though, not to call this 'knowledge'. 'Entitled true belief' is good.
17. Mind and Body / E. Mind as Physical / 2. Reduction of Mind
Studying biology presumes the laws of chemistry, and it could never contradict them [Friend]
     Full Idea: In the hierarchy of reduction, when we investigate questions in biology, we have to assume the laws of chemistry but not of economics. We could never find a law of biology that contradicted something in physics or in chemistry.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 3.1)
     A reaction: This spells out the idea that there is a direction of dependence between aspects of the world, though we should be cautious of talking about 'levels' (see Idea 7003). We cannot choose the direction in which reduction must go.
18. Thought / D. Concepts / 1. Concepts / a. Nature of concepts
Concepts can be presented extensionally (as objects) or intensionally (as a characterization) [Friend]
     Full Idea: The extensional presentation of a concept is just a list of the objects falling under the concept. In contrast, an intensional presentation of a concept gives a characterization of the concept, which allows us to pick out which objects fall under it.
     From: Michèle Friend (Introducing the Philosophy of Mathematics [2007], 3.4)
     A reaction: Logicians seem to favour the extensional view, because (in the standard view) sets are defined simply by their members, so concepts can be explained using sets. I take this to be a mistake. The intensional view seems obviously prior.
22. Metaethics / A. Ethics Foundations / 1. Nature of Ethics / g. Moral responsibility
It is a crime for someone with a violent disposition to get drunk [Mill]
     Full Idea: The making himself drunk, in a person whom drunkenness excites to do harm to others, is a crime against others.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: This principle (based on knowing your own dispositions) is a very good account of the ethics drunkenness. We have a moral duty to know and remember our own dispositions. Violent people should avoid arguments as well as alcohol.
23. Ethics / E. Utilitarianism / 1. Utilitarianism
Ethics rests on utility, which is the permanent progressive interests of people [Mill]
     Full Idea: I regard utility as the ultimate appeal on all ethical questions; but it must be utility in the largest sense, grounded on the permanent interests of a man as a progressive being.
     From: John Stuart Mill (On Liberty [1857], Ch.1)
     A reaction: Mill, writing in praise of personal liberty, is desperate to introduce a paternalistic element into his politics, and the 'maximisation of happiness' will justify such paternalism, while his basic liberal principle (Idea 7211) won't. Mill's Dilemma.
24. Political Theory / A. Basis of a State / 3. Natural Values / a. Natural freedom
Individuals have sovereignty over their own bodies and minds [Mill]
     Full Idea: Over himself, over his own body and mind, the individual is sovereign.
     From: John Stuart Mill (On Liberty [1857], Ch.1)
     A reaction: If I should not even think about evil deeds, then neither should you. I would prevent you if I could. I would prevent you from drinking yourself to death, if I could. It is just that intrusions into private lives leads to greater trouble.
24. Political Theory / B. Nature of a State / 2. State Legitimacy / d. General will
The will of the people is that of the largest or most active part of the people [Mill]
     Full Idea: The will of the people practically means the will of the most numerous or the most active part of the people.
     From: John Stuart Mill (On Liberty [1857], Ch.1)
     A reaction: Hence the nicely coined modern phrase 'the silent majority', on whose behalf certain politicians, usually conservative, offer to speak. It is unlikely that the silent majority are actually deeply opposed to the views of the very active part.
24. Political Theory / C. Ruling a State / 2. Leaders / c. Despotism
It is evil to give a government any more power than is necessary [Mill]
     Full Idea: Government interference should be restricted because of the great evil of adding unnecessarily to its power.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: This would need justification, because it might be replied that individuals should not have unnecessary power either. The main problem is that governments have armies, police and money.
24. Political Theory / C. Ruling a State / 3. Government / a. Government
Individuals often do things better than governments [Mill]
     Full Idea: Government power should be restricted because things are often done better by individuals.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: This contains some truth, but it is obvious that innumerable things can be done better by governments, and also (and more importantly) that innumerable other good things might be done by governments which individuals can't be bothered to do.
24. Political Theory / C. Ruling a State / 4. Changing the State / b. Devolution
Aim for the maximum dissemination of power consistent with efficiency [Mill]
     Full Idea: The safest practical ideal is to aim for the greatest dissemination of power consistent with efficiency.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: This is a very nice principle, which I would think desirable within an institution as well as on the scale of the state. I am becoming a fan of Mill's politics. I still say that freedom is an overrated virtue, so efficiency must be underrated.
24. Political Theory / D. Ideologies / 4. Social Utilitarianism
Maximise happiness by an area of strict privacy, and an area of utilitarian interventions [Mill, by Wolff,J]
     Full Idea: For Mill the greatest happiness will be achieved by giving people a private sphere of interests where no intervention is permitted, while allowing a public sphere where intervention is possible, but only on utilitarian grounds.
     From: report of John Stuart Mill (On Liberty [1857]) by Jonathan Wolff - An Introduction to Political Philosophy (Rev) 4 'Liberty'
     A reaction: This is probably standard liberal practice nowadays. Freely consenting adult sexual activity is agreed to be wholly private. At least some lip-service is paid to increasing happiness when government intervenes.
24. Political Theory / D. Ideologies / 5. Democracy / a. Nature of democracy
People who transact their own business will also have the initiative to control their government [Mill]
     Full Idea: A people accustomed to transacting their own business is certain to be free; it will never let itself be enslaved by any man or body of men because these are able to seize and pull the reins of the central administration.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: He makes reference to Americans. This is an important idea, because it shows that democratic control is not just a matter of elections (which can be abolished or suborned), but is also a characteristic of a certain way of life.
24. Political Theory / D. Ideologies / 6. Liberalism / a. Liberalism basics
Prevention of harm to others is the only justification for exercising power over people [Mill]
     Full Idea: The only purpose for which power can be rightfully exercised over any member of a civilised community, against his will, is to prevent harm to others; his own good, either physical or moral, is not a sufficient warrant.
     From: John Stuart Mill (On Liberty [1857], Ch.1)
     A reaction: This is the key idea in Mill's liberalism, though he goes on to offer some qualifications of this absolute prohibition. I don't disagree with this principle, but there may be a lot more indirect harm than we realise (eg. in allowing liberal sex or drugs).
24. Political Theory / D. Ideologies / 6. Liberalism / b. Liberal individualism
The worth of a State, in the long run, is the worth of the individuals composing it [Mill]
     Full Idea: The worth of a State, in the long run, is the worth of the individuals composing it.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: This is a key idea of liberalism, opposed to any idea that we should abandon our own value to that of our state. I agree, but communitarians can subscribe to this too, while disagreeing that maximum freedom is the strategy to follow.
24. Political Theory / D. Ideologies / 6. Liberalism / d. Liberal freedom
The main argument for freedom is that interference with it is usually misguided [Mill]
     Full Idea: The strongest of all the arguments against the interference of the public with purely personal conduct is that, when it does interfere, the odds are that it interferes wrongly, and in the wrong place.
     From: John Stuart Mill (On Liberty [1857], Ch.4)
     A reaction: This is also a well known objection to capital punishment. Generalised, well established, legal interferences are perhaps more likely to get it right than ad hoc decisions about individuals by individual officials.
25. Social Practice / A. Freedoms / 3. Free speech
Liberty arises at the point where people can freely and equally discuss things [Mill]
     Full Idea: Liberty, as a principle, has no application to any state of things anterior to the time when mankind have become capable of being improved by free and equal discussion.
     From: John Stuart Mill (On Liberty [1857], Ch.1)
     A reaction: There is a Victorian (and Enlightenment) optimism here which a glimpse of the freedoms of the early twenty-first century might dampen. I doubt if Mill expected British tabloid newspapers, or porn on cable TV. Education and freedom connect.
25. Social Practice / A. Freedoms / 5. Freedom of lifestyle
Utilitarianism values liberty, but guides us on which ones we should have or not have [Mill, by Wolff,J]
     Full Idea: Utilitarianism provides an account of what liberties we should and should not have. Mill argues we should be free to compete in trade, but not to use another's property without consent. Thus he sets limits to liberty, while paying it great respect.
     From: report of John Stuart Mill (On Liberty [1857]) by Jonathan Wolff - An Introduction to Political Philosophy (Rev) 4 'Intrinsic'
Mill defends freedom as increasing happiness, but maybe it is an intrinsic good [Wolff,J on Mill]
     Full Idea: Mill has presented liberty as instrumentally valuable, as a way of achieving the greatest possible happiness in society. But perhaps he should have argued that liberty is an intrinsic good, good in itself.
     From: comment on John Stuart Mill (On Liberty [1857]) by Jonathan Wolff - An Introduction to Political Philosophy (Rev) 4 'Intrinsic'
     A reaction: If freedom is intrinsically good, does this leave us (as Wolff warned earlier) unable to defend its value? Freedom isn't an intrinsic good for infants, so why should it be so for adults? Good because it brings happiness, or fulfils our nature?
True freedom is pursuing our own good, while not impeding others [Mill]
     Full Idea: The only freedom which deserves the name, is that of pursuing our own good in our own way, so long as we do not attempt to deprive others of theirs, or impede their efforts to obtain it.
     From: John Stuart Mill (On Liberty [1857], Ch.1)
     A reaction: This principle will probably lead up a Prisoner's Dilemma cul-de-sac. The only freedom which deserves the name is the collective agreed freedom of a whole community to live well, when citizens volunteer to restrict their individual freedoms.
Individuals are not accountable for actions which only concern themselves [Mill]
     Full Idea: My first maxim is that the individual is not accountable to society for his actions, in so far as these concern the interests of no person but himself.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: This is a key idea of liberalism, and one which communitarians have doubts about (because it is almost impossible to perform an action which is of no interest, in the short or long term, to others). I share these doubts.
Blocking entry to an unsafe bridge does not infringe liberty, since no one wants unsafe bridges [Mill]
     Full Idea: An official could turn a person back from an unsafe bridge without infringeing their liberty; for liberty consists in doing what one desires, and he does not desire to fall into the river.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: Seems fair enough, but it justifies paternalist interference. The tricky one is where the official and the citizen disagree over what the citizen 'truly' desires. Asking people may involve too much time, but it could also involve too much effort.
Pimping and running a gambling-house are on the border between toleration and restraint [Mill]
     Full Idea: A person being free to be a pimp, or to keep a gambling-house, lies on the exact boundary line between two principles, of toleration and of restraint.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: Nothing illuminates a philosopher's principles more than for them to specify cases that lie on their borderlines. Both professions seem, unfortunately, to lead people into worse activities, such as violent bullying, or theft. Tricky..
Restraint for its own sake is an evil [Mill]
     Full Idea: All restraint, qua restraint, is an evil.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: The ultimate justification for this is (presumably) utilitarian, but that would mean that there was nothing wrong with restraint if the person did not mind, or was not aware of the restraint. What is intrinsically wrong with restraint?
25. Social Practice / D. Justice / 3. Punishment / a. Right to punish
Society can punish actions which it believes to be prejudicial to others [Mill]
     Full Idea: My second maxim is that for actions that are prejudicial to the interests of others, the individual is accountable, and subject to social or legal punishment, if society believes that this is requisite for its protection.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: (wording compressed). The trouble with this would seem to be the possible disagreement between the individual and the society over whether the actions actually are prejudicial to others. It would justify a conservative society in being repressive.
25. Social Practice / E. Policies / 3. Welfare provision
Benefits performed by individuals, not by government, help also to educate them [Mill]
     Full Idea: It is often desirable that beneficial things should be done by individuals, rather than by the government, as a means to their own mental education.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: This raises the important danger, which even those on the political left must acknowledge, of the 'nanny state'. It offers a nicely paternalistic, and even patronising reason for giving people freedom, just as a parent might to a child.
25. Social Practice / E. Policies / 5. Education / a. Aims of education
We need individual opinions and conduct, and State education is a means to prevent that [Mill]
     Full Idea: Individuality of character, and diversity in opinions and modes of conduct, involves diversity of education; a general State education is a mere contrivance for moulding people to be exactly like one another.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: This strikes me as being particularly true with the advent in Britain of the National Curriculum in the early 1990s. However, if there is a pressure towards conformity in state education, private education is dominated by class and money.
25. Social Practice / F. Life Issues / 3. Abortion
It is a crime to create a being who lacks the ordinary chances of a desirable existence [Mill]
     Full Idea: To bestow a life on someone which may be either a curse or a blessing, unless the being on whom it is to be bestowed will have at least the ordinary chances of a desirable existence, is a crime against that being.
     From: John Stuart Mill (On Liberty [1857], Ch.5)
     A reaction: This is the standard utilitarian attitude to engendering people. I think I have to agree. It is no argument against this to say that we value people with poor life prospects, once they have arrived. Altruism towards children may disguise selfish parents.
29. Religion / B. Monotheistic Religion / 4. Christianity / a. Christianity
The ethics of the Gospel has been supplemented by barbarous Old Testament values [Mill]
     Full Idea: To extract from the Gospel a body of ethical doctrine, has never been possible withouth eking it out from the Old Testament, that is, from a system elaborate indeed, but in many respects barbarous, and intended only for a barbarous people.
     From: John Stuart Mill (On Liberty [1857], Ch.2)
     A reaction: 'Barbarous' has a quaint Victorian ring to it, but his point is that the surviving teachings of Jesus are very thin and generalised. Christians would do better to expand their implications, than to borrow from the Old Testament.