Combining Texts

All the ideas for 'fragments/reports', 'Being and Time' and 'Philosophy of Mathematics'

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88 ideas

1. Philosophy / H. Continental Philosophy / 2. Phenomenology
Being-in-the-world is projection to possibilities, thrownness among them, and fallenness within them [Heidegger, by Caputo]
     Full Idea: Being-in-the-world is a phenomenon of 'care' with a tripartite structure: a) projection towards its possibilities, b) thrownness among those possibilities, so Dasein is not free, and c) fallenness among worldly possibilities, to neglect of its own.
     From: report of Martin Heidegger (Being and Time [1927]) by John D. Caputo - Heidegger p.227
     A reaction: Sounds a bit Californian to me. Just living among the world's possibilities is evidently a bad thing, because you could be concentrating on yourself and your own development instead?
Pheomenology seeks things themselves, without empty theories, problems and concepts [Heidegger]
     Full Idea: 'Phenomenology' can be formulated as 'To the things themselves!' It is opposed to all free-floating constructions and accidental findings, and to conceptions which only seem to have been demonstrated. It is opposed to traditiona' pseudo-problems.
     From: Martin Heidegger (Being and Time [1927], Intro II.07)
     A reaction: It sounds as if we are invited to look at the world the way a dog might look at it. I am not at all clear what it to be gained from this approach.
2. Reason / A. Nature of Reason / 2. Logos
'Logos' really means 'making something manifest' [Heidegger, by Polt]
     Full Idea: Heidegger concludes that 'logos' essentially means 'making something manifest'.
     From: report of Martin Heidegger (Being and Time [1927], 56/33) by Richard Polt - Heidegger: an introduction 3.§7
     A reaction: It would at least seem to involve revealing the truth of something, though truth doesn't seem to be central to Heidegger's thought. 'Logos' is often translated as 'an account', as well as a 'reason', so Heidegger may be right.
2. Reason / D. Definition / 8. Impredicative Definition
Impredicative definitions are wrong, because they change the set that is being defined? [Bostock]
     Full Idea: Poincaré suggested that what is wrong with an impredicative definition is that it allows the set defined to alter its composition as more sets are added to the theory.
     From: David Bostock (Philosophy of Mathematics [2009], 8.3)
3. Truth / A. Truth Problems / 9. Rejecting Truth
Heidegger says truth is historical, and never absolute [Heidegger, by Polt]
     Full Idea: Heidegger is a relentless enemy of ahistorical, absolutist concepts of truth.
     From: report of Martin Heidegger (Being and Time [1927]) by Richard Polt - Heidegger: an introduction 1
     A reaction: I presume that if truth is not absolute then it must be relative, but Polt is a little coy about saying so. For me, anyone who says truth is relative doesn't understand the concept, and is talking about something else.
4. Formal Logic / E. Nonclassical Logics / 2. Intuitionist Logic
Classical interdefinitions of logical constants and quantifiers is impossible in intuitionism [Bostock]
     Full Idea: None of the classical ways of defining one logical constant in terms of others is available in intuitionist logic (and this includes the two quantifiers).
     From: David Bostock (Philosophy of Mathematics [2009], 7.2)
4. Formal Logic / F. Set Theory ST / 1. Set Theory
There is no single agreed structure for set theory [Bostock]
     Full Idea: There is so far no agreed set of axioms for set theory which is categorical, i.e. which does pick just one structure.
     From: David Bostock (Philosophy of Mathematics [2009], 6.4)
     A reaction: This contrasts with Peano Arithmetic, which is categorical in its second-order version.
4. Formal Logic / F. Set Theory ST / 3. Types of Set / a. Types of set
A 'proper class' cannot be a member of anything [Bostock]
     Full Idea: A 'proper class' cannot be a member of anything, neither of a set nor of another proper class.
     From: David Bostock (Philosophy of Mathematics [2009], 5.4)
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / a. Axioms for sets
We could add axioms to make sets either as small or as large as possible [Bostock]
     Full Idea: We could add the axiom that all sets are constructible (V = L), making the universe of sets as small as possible, or add the axiom that there is a supercompact cardinal (SC), making the universe as large as we no know how to.
     From: David Bostock (Philosophy of Mathematics [2009], 6.4)
     A reaction: Bostock says most mathematicians reject the first option, and are undecided about the second option.
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / j. Axiom of Choice IX
The Axiom of Choice relies on reference to sets that we are unable to describe [Bostock]
     Full Idea: The usual accounts of ZF are not restricted to subsets that we can describe, and that is what justifies the axiom of choice.
     From: David Bostock (Philosophy of Mathematics [2009], 8.4 n36)
     A reaction: This contrasts interestingly with predicativism, which says we can only discuss things which we can describe or define. Something like verificationism hovers in the background.
4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / f. Limitation of Size
Replacement enforces a 'limitation of size' test for the existence of sets [Bostock]
     Full Idea: The Axiom of Replacement (or the Axiom of Subsets, 'Aussonderung', Fraenkel 1922) in effect enforces the idea that 'limitation of size' is a crucial factor when deciding whether a proposed set or does not not exist.
     From: David Bostock (Philosophy of Mathematics [2009], 5.4)
5. Theory of Logic / A. Overview of Logic / 5. First-Order Logic
First-order logic is not decidable: there is no test of whether any formula is valid [Bostock]
     Full Idea: First-order logic is not decidable. That is, there is no test which can be applied to any arbitrary formula of that logic and which will tell one whether the formula is or is not valid (as proved by Church in 1936).
     From: David Bostock (Philosophy of Mathematics [2009], 5.5)
The completeness of first-order logic implies its compactness [Bostock]
     Full Idea: From the fact that the usual rules for first-level logic are complete (as proved by Gödel 1930), it follows that this logic is 'compact'.
     From: David Bostock (Philosophy of Mathematics [2009], 5.5)
     A reaction: The point is that the completeness requires finite proofs.
5. Theory of Logic / G. Quantification / 4. Substitutional Quantification
Substitutional quantification is just standard if all objects in the domain have a name [Bostock]
     Full Idea: Substitutional quantification and quantification understood in the usual 'ontological' way will coincide when every object in the (ontological) domain has a name.
     From: David Bostock (Philosophy of Mathematics [2009], 7.3 n23)
5. Theory of Logic / H. Proof Systems / 4. Natural Deduction
The Deduction Theorem is what licenses a system of natural deduction [Bostock]
     Full Idea: The Deduction Theorem is what licenses a system of 'natural deduction' in the first place.
     From: David Bostock (Philosophy of Mathematics [2009], 7.2)
5. Theory of Logic / L. Paradox / 4. Paradoxes in Logic / c. Berry's paradox
Berry's Paradox considers the meaning of 'The least number not named by this name' [Bostock]
     Full Idea: Berry's Paradox can be put in this form, by considering the alleged name 'The least number not named by this name'.
     From: David Bostock (Philosophy of Mathematics [2009], 8.1)
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / b. Types of number
Each addition changes the ordinality but not the cardinality, prior to aleph-1 [Bostock]
     Full Idea: If you add to the ordinals you produce many different ordinals, each measuring the length of the sequence of ordinals less than it. They each have cardinality aleph-0. The cardinality eventually increases, but we can't say where this break comes.
     From: David Bostock (Philosophy of Mathematics [2009], 4.5)
ω + 1 is a new ordinal, but its cardinality is unchanged [Bostock]
     Full Idea: If we add ω onto the end of 0,1,2,3,4..., it then has a different length, of ω+1. It has a different ordinal (since it can't be matched with its first part), but the same cardinal (since adding 1 makes no difference).
     From: David Bostock (Philosophy of Mathematics [2009], 4.5)
     A reaction: [compressed] The ordinals and cardinals coincide up to ω, but this is the point at which they come apart.
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / c. Priority of numbers
A cardinal is the earliest ordinal that has that number of predecessors [Bostock]
     Full Idea: It is the usual procedure these days to identify a cardinal number with the earliest ordinal number that has that number of predecessors.
     From: David Bostock (Philosophy of Mathematics [2009], 4.5)
     A reaction: This sounds circular, since you need to know the cardinal in order to decide which ordinal is the one you want, but, hey, what do I know?
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / f. Cardinal numbers
Aleph-1 is the first ordinal that exceeds aleph-0 [Bostock]
     Full Idea: The cardinal aleph-1 is identified with the first ordinal to have more than aleph-0 members, and so on.
     From: David Bostock (Philosophy of Mathematics [2009], 5.4)
     A reaction: That is, the succeeding infinite ordinals all have the same cardinal number of members (aleph-0), until the new total is triggered (at the number of the reals). This is Continuum Hypothesis territory.
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / g. Real numbers
Instead of by cuts or series convergence, real numbers could be defined by axioms [Bostock]
     Full Idea: In addition to cuts, or converging series, Cantor suggests we can simply lay down a set of axioms for the real numbers, and this can be done without any explicit mention of the rational numbers [note: the axioms are those for a complete ordered field].
     From: David Bostock (Philosophy of Mathematics [2009], 4.4)
     A reaction: It is interesting when axioms are best, and when not. Set theory depends entirely on axioms. Horsten and Halbach are now exploring treating truth as axiomatic. You don't give the 'nature' of the thing - just rules for its operation.
The number of reals is the number of subsets of the natural numbers [Bostock]
     Full Idea: It is not difficult to show that the number of the real numbers is the same as the number of all the subsets of the natural numbers.
     From: David Bostock (Philosophy of Mathematics [2009], 4.5)
     A reaction: The Continuum Hypothesis is that this is the next infinite number after the number of natural numbers. Why can't there be a number which is 'most' of the subsets of the natural numbers?
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / i. Reals from cuts
For Eudoxus cuts in rationals are unique, but not every cut makes a real number [Bostock]
     Full Idea: As Eudoxus claimed, two distinct real numbers cannot both make the same cut in the rationals, for any two real numbers must be separated by a rational number. He did not say, though, that for every such cut there is a real number that makes it.
     From: David Bostock (Philosophy of Mathematics [2009], 4.4)
     A reaction: This is in Bostock's discussion of Dedekind's cuts. It seems that every cut is guaranteed to produce a real. Fine challenges the later assumption.
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / k. Infinitesimals
Infinitesimals are not actually contradictory, because they can be non-standard real numbers [Bostock]
     Full Idea: Non-standard natural numbers will yield non-standard rational and real numbers. These will include reciprocals which will be closer to 0 than any standard real number. These are like 'infinitesimals', so that notion is not actually a contradiction.
     From: David Bostock (Philosophy of Mathematics [2009], 5.5)
6. Mathematics / B. Foundations for Mathematics / 3. Axioms for Geometry
Modern axioms of geometry do not need the real numbers [Bostock]
     Full Idea: A modern axiomatisation of geometry, such as Hilbert's (1899), does not need to claim the existence of real numbers anywhere in its axioms.
     From: David Bostock (Philosophy of Mathematics [2009], 9.B.5.ii)
     A reaction: This is despite the fact that geometry is reduced to algebra, and the real numbers are the equivalent of continuous lines. Bostock votes for a Greek theory of proportion in this role.
6. Mathematics / B. Foundations for Mathematics / 4. Axioms for Number / d. Peano arithmetic
The Peano Axioms describe a unique structure [Bostock]
     Full Idea: The Peano Axioms are categorical, meaning that they describe a unique structure.
     From: David Bostock (Philosophy of Mathematics [2009], 4.4 n20)
     A reaction: So if you think there is nothing more to the natural numbers than their structure, then the Peano Axioms give the essence of arithmetic. If you think that 'objects' must exist to generate a structure, there must be more to the numbers.
6. Mathematics / B. Foundations for Mathematics / 5. Definitions of Number / d. Hume's Principle
Hume's Principle is a definition with existential claims, and won't explain numbers [Bostock]
     Full Idea: Hume's Principle will not do as an implicit definition because it makes a positive claim about the size of the universe (which no mere definition can do), and because it does not by itself explain what the numbers are.
     From: David Bostock (Philosophy of Mathematics [2009], 9.A.2)
Many things will satisfy Hume's Principle, so there are many interpretations of it [Bostock]
     Full Idea: Hume's Principle gives a criterion of identity for numbers, but it is obvious that many other things satisfy that criterion. The simplest example is probably the numerals (in any notation, decimal, binary etc.), giving many different interpretations.
     From: David Bostock (Philosophy of Mathematics [2009], 9.A.2)
There are many criteria for the identity of numbers [Bostock]
     Full Idea: There is not just one way of giving a criterion of identity for numbers.
     From: David Bostock (Philosophy of Mathematics [2009], 9.A.2)
6. Mathematics / B. Foundations for Mathematics / 5. Definitions of Number / e. Caesar problem
Frege makes numbers sets to solve the Caesar problem, but maybe Caesar is a set! [Bostock]
     Full Idea: The Julius Caesar problem was one reason that led Frege to give an explicit definition of numbers as special sets. He does not appear to notice that the same problem affects his Axiom V for introducing sets (whether Caesar is or is not a set).
     From: David Bostock (Philosophy of Mathematics [2009], 9.A.2)
     A reaction: The Julius Caesar problem is a sceptical acid that eats into everything in philosophy of mathematics. You give all sorts of wonderful accounts of numbers, but at what point do you know that you now have a number, and not something else?
6. Mathematics / B. Foundations for Mathematics / 7. Mathematical Structuralism / e. Structuralism critique
Numbers can't be positions, if nothing decides what position a given number has [Bostock]
     Full Idea: There is no ground for saying that a number IS a position, if the truth is that there is nothing to determine which number is which position.
     From: David Bostock (Philosophy of Mathematics [2009], 6.4)
     A reaction: If numbers lose touch with the empirical ability to count physical objects, they drift off into a mad world where they crumble away.
Structuralism falsely assumes relations to other numbers are numbers' only properties [Bostock]
     Full Idea: Structuralism begins from a false premise, namely that numbers have no properties other than their relations to other numbers.
     From: David Bostock (Philosophy of Mathematics [2009], 6.5)
     A reaction: Well said. Describing anything purely relationally strikes me as doomed, because you have to say why those things relate in those ways.
6. Mathematics / C. Sources of Mathematics / 3. Mathematical Nominalism
Nominalism about mathematics is either reductionist, or fictionalist [Bostock]
     Full Idea: Nominalism has two main versions, one which tries to 'reduce' the objects of mathematics to something simpler (Russell and Wittgenstein), and another which claims that such objects are mere 'fictions' which have no reality (Field).
     From: David Bostock (Philosophy of Mathematics [2009], 9)
Nominalism as based on application of numbers is no good, because there are too many applications [Bostock]
     Full Idea: The style of nominalism which aims to reduce statements about numbers to statements about their applications does not work for the natural numbers, because they have many applications, and it is arbitrary to choose just one of them.
     From: David Bostock (Philosophy of Mathematics [2009], 9.B.5.iii)
6. Mathematics / C. Sources of Mathematics / 4. Mathematical Empiricism / b. Indispensability of mathematics
Actual measurement could never require the precision of the real numbers [Bostock]
     Full Idea: We all know that in practice no physical measurement can be 100 per cent accurate, and so it cannot require the existence of a genuinely irrational number, rather than some of the rational numbers close to it.
     From: David Bostock (Philosophy of Mathematics [2009], 9.A.3)
6. Mathematics / C. Sources of Mathematics / 5. Numbers as Adjectival
Ordinals are mainly used adjectively, as in 'the first', 'the second'... [Bostock]
     Full Idea: The basic use of the ordinal numbers is their use as ordinal adjectives, in phrases such as 'the first', 'the second' and so on.
     From: David Bostock (Philosophy of Mathematics [2009], 9.5.iii)
     A reaction: That is because ordinals seem to attach to particulars, whereas cardinals seem to attach to groups. Then you say 'three is greater than four', it is not clear which type you are talking about.
6. Mathematics / C. Sources of Mathematics / 6. Logicism / b. Type theory
Simple type theory has 'levels', but ramified type theory has 'orders' [Bostock]
     Full Idea: The simple theory of types distinguishes sets into different 'levels', but this is quite different from the distinction into 'orders' which is imposed by the ramified theory.
     From: David Bostock (Philosophy of Mathematics [2009], 8.1)
     A reaction: The ramified theory has both levels and orders (p.235). Russell's terminology is, apparently, inconsistent.
6. Mathematics / C. Sources of Mathematics / 6. Logicism / c. Neo-logicism
Neo-logicists agree that HP introduces number, but also claim that it suffices for the job [Bostock]
     Full Idea: The neo-logicists take up Frege's claim that Hume's Principle introduces a new concept (of a number), but unlike Frege they go on to claim that it by itself gives a complete account of that concept.
     From: David Bostock (Philosophy of Mathematics [2009], 9.A.2)
     A reaction: So the big difference between Frege and neo-logicists is the Julius Caesar problem.
Neo-logicists meet the Caesar problem by saying Hume's Principle is unique to number [Bostock]
     Full Idea: The response of neo-logicists to the Julius Caesar problem is to strengthen Hume's Principle in the hope of ensuring that only numbers will satisfy it. They say the criterion of identity provided by HP is essential to number, and not to anything else.
     From: David Bostock (Philosophy of Mathematics [2009], 9.A.2)
6. Mathematics / C. Sources of Mathematics / 6. Logicism / d. Logicism critique
If Hume's Principle is the whole story, that implies structuralism [Bostock]
     Full Idea: If Hume's Principle is all we are given, by way of explanation of what the numbers are, the only conclusion to draw would seem to be the structuralists' conclusion, ...studying all systems that satisfy that principle.
     From: David Bostock (Philosophy of Mathematics [2009], 9.A.2)
     A reaction: Any approach that implies a set of matching interpretations will always imply structuralism. To avoid it, you need to pin the target down uniquely.
Many crucial logicist definitions are in fact impredicative [Bostock]
     Full Idea: Many of the crucial definitions in the logicist programme are in fact impredicative.
     From: David Bostock (Philosophy of Mathematics [2009], 8.2)
Treating numbers as objects doesn't seem like logic, since arithmetic fixes their totality [Bostock]
     Full Idea: If logic is neutral on the number of objects there are, then logicists can't construe numbers as objects, for arithmetic is certainly not neutral on the number of numbers there are. They must be treated in some other way, perhaps as numerical quantifiers.
     From: David Bostock (Philosophy of Mathematics [2009], 5.5)
6. Mathematics / C. Sources of Mathematics / 9. Fictional Mathematics
Higher cardinalities in sets are just fairy stories [Bostock]
     Full Idea: In its higher reaches, which posit sets of huge cardinalities, set theory is just a fairy story.
     From: David Bostock (Philosophy of Mathematics [2009], 9.5.iii)
     A reaction: You can't say the higher reaches are fairy stories but the lower reaches aren't, if the higher is directly derived from the lower. The empty set and the singleton are fairy stories too. Bostock says the axiom of infinity triggers the fairy stories.
A fairy tale may give predictions, but only a true theory can give explanations [Bostock]
     Full Idea: A common view is that although a fairy tale may provide very useful predictions, it cannot provide explanations for why things happen as they do. In order to do that a theory must also be true (or, at least, an approximation to the truth).
     From: David Bostock (Philosophy of Mathematics [2009], 9.B.5)
     A reaction: Of course, fictionalism offers an explanation of mathematics as a whole, but not of the details (except as the implications of the initial fictional assumptions).
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / c. Conceptualism
The best version of conceptualism is predicativism [Bostock]
     Full Idea: In my personal opinion, predicativism is the best version of conceptualism that we have yet discovered.
     From: David Bostock (Philosophy of Mathematics [2009], 8.4)
     A reaction: Since conceptualism is a major player in the field, this makes predicativism a very important view. I won't vote Predicativist quite yet, but I'm tempted.
Conceptualism fails to grasp mathematical properties, infinity, and objective truth values [Bostock]
     Full Idea: Three simple objections to conceptualism in mathematics are that we do not ascribe mathematical properties to our ideas, that our ideas are presumably finite, and we don't think mathematics lacks truthvalue before we thought of it.
     From: David Bostock (Philosophy of Mathematics [2009], 8.4)
     A reaction: [compressed; Bostock refers back to his Ch 2] Plus Idea 18134. On the whole I sympathise with conceptualism, so I will not allow myself to be impressed by any of these objections. (So, what's actually wrong with them.....?).
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / d. Predicativism
If abstracta only exist if they are expressible, there can only be denumerably many of them [Bostock]
     Full Idea: If an abstract object exists only when there is some suitable way of expressing it, then there are at most denumerably many abstract objects.
     From: David Bostock (Philosophy of Mathematics [2009], 8.2)
     A reaction: Fine by me. What an odd view, to think there are uncountably many abstract objects in existence, only a countable portion of which will ever be expressed! [ah! most people agree with me, p.243-4]
Predicativism makes theories of huge cardinals impossible [Bostock]
     Full Idea: Classical mathematicians say predicative mathematics omits areas of great interest, all concerning non-denumerable real numbers, such as claims about huge cardinals. There cannot be a predicative version of this theory.
     From: David Bostock (Philosophy of Mathematics [2009], 8.3)
     A reaction: I'm not sure that anyone will really miss huge cardinals if they are prohibited, though cryptography seems to flirt with such things. Are we ever allowed to say that some entity conjured up by mathematicians is actually impossible?
If mathematics rests on science, predicativism may be the best approach [Bostock]
     Full Idea: It has been claimed that only predicative mathematics has a justification through its usefulness to science (an empiricist approach).
     From: David Bostock (Philosophy of Mathematics [2009], 8.3)
     A reaction: [compressed. Quine is the obvious candidate] I suppose predicativism gives your theory roots, whereas impredicativism is playing an abstract game.
If we can only think of what we can describe, predicativism may be implied [Bostock]
     Full Idea: If we accept the initial idea that we can think only of what we ourselves can describe, then something like the theory of predicativism quite naturally results
     From: David Bostock (Philosophy of Mathematics [2009], 8.3)
     A reaction: I hate the idea that we can only talk of what falls under a sortal, but 'what we can describe' is much more plausible. Whether or not you agree with this approach (I'm pondering it), this makes predicativism important.
The usual definitions of identity and of natural numbers are impredicative [Bostock]
     Full Idea: The predicative approach cannot accept either the usual definition of identity or the usual definition of the natural numbers, for both of these definitions are impredicative.
     From: David Bostock (Philosophy of Mathematics [2009], 8.3)
     A reaction: [Bostock 237-8 gives details]
The predicativity restriction makes a difference with the real numbers [Bostock]
     Full Idea: It is with the real numbers that the restrictions imposed by predicativity begin to make a real difference.
     From: David Bostock (Philosophy of Mathematics [2009], 8.3)
7. Existence / A. Nature of Existence / 3. Being / a. Nature of Being
Reducing being to the study of beings too readily accepts the modern scientific view [Heidegger, by May]
     Full Idea: Continental philosophers, following Heidegger, see in the attempt to reduce the question of being to that of beings a symptom of an age that is too ready to accept the terms in which science conceives the world.
     From: report of Martin Heidegger (Being and Time [1927]) by Todd May - Gilles Deleuze 1.04
     A reaction: Interesting. I take the idea that this is a failing of the modern age to be ridiculous, since I take it to be the key metaphysical move made by Aristotle. Neverthless, Aristotle is closely in tune with modern science. For 'beings', read 'objects'.
For us, Being is constituted by awareness of other sorts of Being [Heidegger]
     Full Idea: We are Dasein - the entity who possesses - as constitutive for its understanding of existence - an understanding of the Being of all entities of a character other than its own.
     From: Martin Heidegger (Being and Time [1927], 34/13), quoted by Richard Polt - Heidegger: an introduction 3.§4
     A reaction: This seems to connect to the emerging 'externalist' view of mind that comes with the external view of content coming from Purnam's Twin Earth idea.
7. Existence / A. Nature of Existence / 3. Being / h. Dasein (being human)
Heidegger turns to 'Being' to affirm the uniqueness of humans in the world [Heidegger, by Gray]
     Full Idea: Heidegger turns to 'Being' for the same reason that Christians turn to God - to affirm the unique place of humans in the world.
     From: report of Martin Heidegger (Being and Time [1927]) by John Gray - Straw Dogs 2.4
     A reaction: This is the first remark I have encountered that makes sense of Heidegger's Being to me! It places Heidegger as a modernist philosopher, trying to grapple with the decline of religion. I'll stick with Bertrand Russell on that.
Dasein is a mode of Being distinguished by concern for its own Being [Heidegger]
     Full Idea: Dasein is an entity which does not just occur among other entities. Rather it is ontically distinguished by the fact that, in its very Being, that Being is an issue for it.
     From: Martin Heidegger (Being and Time [1927], Intro I.04)
     A reaction: How do you distinguish the Being of normal humans from the Being of someone in a deep coma, who has no existential issues? Has that Dasein ceased to be? Why does angst create a new mode of Being, but flying doesn't?
Dasein is ahead of itself in the world, and alongside encountered entities [Heidegger]
     Full Idea: The formal existential totality of Dasein's ontological structural whole is: the Being of Dasein means ahead-of-itself-Being-already-in-(the-world) as Being-alongside (entities encountered within-the-world).
     From: Martin Heidegger (Being and Time [1927], I.6 41)
     A reaction: If you find that thought really illuminating, you are probably on the wrong website. However, the thought that we exist 'ahead of ourselves' might be a fruitful line for existentialists to explore.
In company with others one's Dasein dissolves, and even the others themselves dissolve [Heidegger]
     Full Idea: This being-with-one-another dissolves one's own Dasein completely into the kind of being of 'the others', in such a way, indeed, that the others, as distinguishable and explicit, vanish more and more.
     From: Martin Heidegger (Being and Time [1927], p.164), quoted by Mark Wrathall - Heidegger: how to read 5
     A reaction: He seems to be describing the psychology of someone who joins a small crowd which gradually increases in size. I take this relation to others to be the basic existential dilemma, of retaining individual authenticity within a community.
'Dasein' expresses not 'what' the entity is, but its being [Heidegger]
     Full Idea: When we designate this entity with the term 'Dasein' we are expressing not its 'what' (as if it were a table, house, or tree) but its being.
     From: Martin Heidegger (Being and Time [1927], p.297), quoted by Kevin Aho - Existentialism: an introduction 2 'Phenomenology'
     A reaction: Presumably analytic discussions of persons try to be too objective. Heidegger is trying to capture the thought at the heart of Kierkegaard's existentialism. Objectivity and subjectivity are never in conflict. Is there really a different mode of existence?
The word 'dasein' is used to mean 'the manner of Being which man possesses', and also the human creature [Heidegger, by Cooper,DE]
     Full Idea: Heidegger borrows a common German word 'dasein', meaning 'being' or 'existence', to refer both to 'the manner of Being which... man... possesses', and to the creature which possesses it.
     From: report of Martin Heidegger (Being and Time [1927], p.32) by David E. Cooper - Heidegger Ch.3
     A reaction: This just strikes me as an elementary ontological mistake. Because something has startling properties it doesn't follow that we have a different type of Being. Magnets don't have a different type of being from ordinary iron.
'Dasein' is Being which is laid claim to, and which matters to its owner [Heidegger, by Cooper,DE]
     Full Idea: We each of us not only have Dasein (our kind of Being), but we can lay claim to it. Also the Dasein of a thing 'is an issue for it' - we care about the kinds of creatures we can make ourselves into.
     From: report of Martin Heidegger (Being and Time [1927], p.67) by David E. Cooper - Heidegger Ch.3
     A reaction: Heidegger says other more puzzling things about Dasein. The second half of the idea is what makes Heidegger an existentialist, and an inspiration for Sartre.
Dasein is being which can understand itself, and possess itself in a way allowing authenticity [Heidegger]
     Full Idea: Dasein is an entity which, in its very being, comports itself understandingly towards that being. ...Mineness belongs to an existent Dasein, and belongs to it as the condition which makes authenticity and inauthenticity possible.
     From: Martin Heidegger (Being and Time [1927], p.78), quoted by Mark Wrathall - Heidegger: how to read 1
     A reaction: He might eventually persuade me that Dasein is so different from mere material being that it deserves a category of its own. But a reductive account of mind is also a reductive account of being.
7. Existence / A. Nature of Existence / 6. Criterion for Existence
Ontology is possible only as phenomenology [Heidegger]
     Full Idea: Ontology is possible only as phenomenology.
     From: Martin Heidegger (Being and Time [1927], p.31), quoted by Dale Jacquette - Ontology Ch.1
     A reaction: Jacquette argues against this claim. The idea seems to be the ultimate extension of Kant, and it is not a big move to say that the only real phenomenology we can discuss is our semantics. Wrong, wrong, wrong.
7. Existence / D. Theories of Reality / 3. Reality
Readiness-to-hand defines things in themselves ontologically [Heidegger]
     Full Idea: Readiness-to-hand is the way in which entities as they are 'in themselves' are defined ontologico-categorially.
     From: Martin Heidegger (Being and Time [1927], I.3.15)
     A reaction: I assume this is a direct reference to the problem idealists had with the thing-in-itself. It seems that the reality of a thing consists of the strengthened relationship it has with Dasein, which sounds fairly idealist to me.
9. Objects / D. Essence of Objects / 1. Essences of Objects
Heidegger seeks a non-traditional concept of essence as 'essential unfolding' [Heidegger, by Polt]
     Full Idea: Heidegger tries to develop a non-traditional concept of essence as 'essential unfolding' ('wesen' as a verb).
     From: report of Martin Heidegger (Being and Time [1927], I.4.27) by Richard Polt - Heidegger: an introduction 3.§25-7
11. Knowledge Aims / A. Knowledge / 2. Understanding
Propositions don't provide understanding, because the understanding must come first [Heidegger, by Polt]
     Full Idea: Propositions are not a good clue to the essence of understanding, because we must already understand things before we formulate propositions about them.
     From: report of Martin Heidegger (Being and Time [1927], I.5.31) by Richard Polt - Heidegger: an introduction 3.§31-3
     A reaction: I like this, because I think the most important aspects of our thought and understanding are entirely non-verbal - even in cases where they seem to be highly specific and verbal. We don't understand ourselves at all!
11. Knowledge Aims / B. Certain Knowledge / 5. Cogito Critique
If we posit 'I' as the starting point, we miss the mind's phenomenal content [Heidegger]
     Full Idea: One of our first tasks will be to prove that if we posit an 'I' or subject as that which is proximally given, we shall completely miss the phenomenal content of Dasein.
     From: Martin Heidegger (Being and Time [1927], I.1.10)
     A reaction: Descartes had thrown doubt on the informativeness of the phenomena, so presumably your phenomenologist is not interested in whether they reveal any truth. So why are unreliable phenomena of any interest?
11. Knowledge Aims / C. Knowing Reality / 1. Perceptual Realism / b. Direct realism
Our relationship to a hammer strengthens when we use [Heidegger]
     Full Idea: The less we stare at the hammer-Thing, and the more we seize hold of it and use it, the more primordial does our relationship to it become. ...The kind of Being which equipment possesses... we call 'readiness-to-hand' [Zuhandenheit].
     From: Martin Heidegger (Being and Time [1927], I.3.15)
     A reaction: This example would be well at home in the writings of the pragmatists. It is also an important example for existentialists. In analytic philosophy we might say the experience combines perception with direct exerience of causation.
12. Knowledge Sources / B. Perception / 4. Sense Data / d. Sense-data problems
There are no raw sense-data - our experiences are of the sound or colour of something [Heidegger]
     Full Idea: We always take a noise as the sound of something; we always take a hue as the color of something. We simply do not experience raw, uninterpreted sense-data - these are the inventions of philosophers.
     From: Martin Heidegger (Being and Time [1927], 207/163-4), quoted by Richard Polt - Heidegger: an introduction 3.§31-3
     A reaction: This is something like the modern view of sense-data as promoted by John McDowell, rather than the experiential atoms of Russell and Moore. Experience is holistic, but that doesn't mean we can't analyse it into components.
12. Knowledge Sources / B. Perception / 5. Interpretation
Perceived objects always appear in a context [Heidegger]
     Full Idea: The perceptual 'something' is always in the middle of something else, it always forms part of a 'field'.
     From: Martin Heidegger (Being and Time [1927], p.4), quoted by Kevin Aho - Existentialism: an introduction 3 'Perceptual'
     A reaction: Sounds like our knowledge of electrons. Nice point. Standard analytic discussions of perceiving a glass always treat it in isolation, when it is on an expensive table near a brandy bottle. Or near a hammer.
13. Knowledge Criteria / D. Scepticism / 6. Scepticism Critique
The scandal of philosophy is expecting to prove reality when the prover's Being is vague [Heidegger]
     Full Idea: The 'scandal of philosophy' is not that this proof [of external things] has yet to be given, but that such proofs are expected and attempted again and again. ...The kind of Being of the entity which does the proving has not been made definite enough.
     From: Martin Heidegger (Being and Time [1927], I.6.43a)
     A reaction: The 'scandal' was a remark of Kant's. Presumably Heidegger's exploration of Dasein aims to establish the Being of the prover sufficiently to solve this problem (via phenomenology).
15. Nature of Minds / A. Nature of Mind / 1. Mind / b. Purpose of mind
Having thoughts and feelings need engagement in the world [Heidegger, by Wrathall]
     Full Idea: Heidegger argues that having thoughts and feelings is only possible for entity that is actually engaged in the world.
     From: report of Martin Heidegger (Being and Time [1927]) by Mark Wrathall - Heidegger: how to read 1
     A reaction: This seems to be an a priori exclusion of the possibility of a brain in a vat. I guess the ancestor of this idea is Schopenhauer.
15. Nature of Minds / A. Nature of Mind / 4. Other Minds / c. Knowing other minds
Dasein finds itself already amongst others [Heidegger, by Caputo]
     Full Idea: The world is a world shared with others, so that far from being a solipsistic ego ...Dasein finds itself already amongst others.
     From: report of Martin Heidegger (Being and Time [1927]) by John D. Caputo - Heidegger p.226
     A reaction: Phenomenologists don't seem bothered about the problem of knowing other minds. If you take something for granted, it ceases to be a problem to be solved!
If we work and play with other people, they are bound to be 'Dasein', intelligent agents [Heidegger, by Cooper,DE]
     Full Idea: How do I know that other people have minds? The question is a bad one. Precisely because I encounter them at work, play and the like, it is guaranteed that they, too, are Dasein, intelligent agents.
     From: report of Martin Heidegger (Being and Time [1927], p.153-) by David E. Cooper - Heidegger Ch.3
     A reaction: I've seen film of someone playing peek-a-boo with a bonobo ape, so presumably they have Dasein. It might be easier for the AI community to aim at building a robot with Dasein, than one which was simply conscious.
15. Nature of Minds / A. Nature of Mind / 6. Anti-Individualism
When Dasein grasps something it exists externally alongside the thing [Heidegger]
     Full Idea: When Dasein directs itself towards something and grasps it, it does not somehow first get out of an inner sphere in which it has been proximally encapsulated, but its primary kind of Being is such that it is always 'outside' alongside entities.
     From: Martin Heidegger (Being and Time [1927], I.2.13)
     A reaction: This is the first plausible fruit of phenomenology I have been able to discover. Analysing the passive mind is not very promising, but seeing what happens when we become more proactive is revealing.
16. Persons / C. Self-Awareness / 2. Knowing the Self
There is an everyday self, and an authentic self, when it is grasped in its own way [Heidegger]
     Full Idea: The self of everyday Dasein is the they-self [das Man-selbst], which we distinguish from the authentic self - that is, from the Self which has been taken hold of in its own way.
     From: Martin Heidegger (Being and Time [1927], I.4.27)
     A reaction: To a novice this sounds like a requirement for increased self-consciousness during daily activity. 'Be a good animal, true to your animal self' said one of Lawrence's characters.
16. Persons / E. Rejecting the Self / 4. Denial of the Self
Everyone is other, and no one is himself [Heidegger]
     Full Idea: Everyone is other, and no one is himself.
     From: Martin Heidegger (Being and Time [1927], p.165), quoted by Rüdiger Safranski - Nietzsche: a philosophical biography 09
     A reaction: Safranski describes this as the idea of 'structural self-evasion'. He detects the same idea in Nietzsche's 'Daybreak'.
18. Thought / A. Modes of Thought / 3. Emotions / c. Role of emotions
Moods are more fundamentally revealing than theories - as when fear reveals a threat [Heidegger, by Polt]
     Full Idea: For Heidegger moods are disclosive; they show us things in a more fundamental way than theoretical propositions ever can. For example, fear reveals something as a threat.
     From: report of Martin Heidegger (Being and Time [1927], I.5.30) by Richard Polt - Heidegger: an introduction 3.§30
     A reaction: Most modern students of emotion seem to agree. Even though they may not have specific content, it is always possible to consider the underlying cause of the mood.
19. Language / F. Communication / 2. Assertion
In logic a proposition means the same when it is and when it is not asserted [Bostock]
     Full Idea: In Modus Ponens where the first premise is 'P' and the second 'P→Q', in the first premise P is asserted but in the second it is not. Yet it must mean the same in both premises, or it would be guilty of the fallacy of equivocation.
     From: David Bostock (Philosophy of Mathematics [2009], 7.2)
     A reaction: This is Geach's thought (leading to an objection to expressivism in ethics, that P means the same even if it is not expressed).
22. Metaethics / B. Value / 1. Nature of Value / b. Fact and value
We do not add value to naked things; its involvement is disclosed in understanding it [Heidegger]
     Full Idea: We do not throw a 'signification' over some naked thing which is present-at-hand, we do not stick a value on it; but when something is encountered as such, the thing in question has an involvement which is disclosed in our understanding of the world.
     From: Martin Heidegger (Being and Time [1927], p.190-1), quoted by George Dickie - The Myth of the Aesthetic Attitude 3 'Undoing'
     A reaction: Analytic philosophy and science have tried to dismantle experience, and Heidegger wants to put it back together. I would say there is a big difference between encountering a thing (which is a bit facty), and understanding it (which is more valuey).
23. Ethics / F. Existentialism / 1. Existentialism
Dasein has the potential to be itself, but must be shown this in the midst of ordinariness [Heidegger]
     Full Idea: Because Dasein is lost in the 'they', it must first find itself. It must be 'shown' to itself in its possible authenticity. In terms of its possibility, Dasein is already a potentiality-for-Being-its-self, but it needs to have this potentiality attested.
     From: Martin Heidegger (Being and Time [1927], II.2.54)
     A reaction: I wish there was some criterion for knowing when you are being yourself and when you are not.
23. Ethics / F. Existentialism / 3. Angst
Anxiety reveals the possibility and individuality of Dasein [Heidegger]
     Full Idea: Anxiety discloses Dasein as Being-possible, and indeed as the only kind of thing which it can be of its own accord as something individualised in individualisation.
     From: Martin Heidegger (Being and Time [1927], I.6.40)
     A reaction: Is sounds like insecurity, as a sort of trauma that shocks one into self-realisation. The idea means very little to me personally.
Anxiety about death frees me to live my own life [Heidegger, by Wrathall]
     Full Idea: For Heidegger, as a consequence of my anxiety in the face of death, I am set free to live my life as my own rather than doing things merely because others expect me to do them.
     From: report of Martin Heidegger (Being and Time [1927]) by Mark Wrathall - Heidegger: how to read 7
     A reaction: Contrary to Epicurus, Heidegger thinks anxiety about death is a good thing. The point is, I suppose, that we all die alone, and people who are very socially contrained need to face up to death in order to grasp their autonomy.
Anxiety is the uncanniness felt when constantly fleeing from asserting one's own freedom [Heidegger, by Caputo]
     Full Idea: Anxiety [angst] is the disturbing sense of uncanniness by which Dasein is overtaken (thrownness) when it discovers there is nothing other than its own freedom to sustain its projects (projection), and from which Dasein constantly takes flight (falling).
     From: report of Martin Heidegger (Being and Time [1927]) by John D. Caputo - Heidegger p.227
     A reaction: This seems to be Kierkegaard's idea, unamended. In my experience anxiety only comes when I am forced into making decisions by worldly situations. An 'existential crisis' is a sort of blankness appearing where a future life was supposed to be.
23. Ethics / F. Existentialism / 5. Existence-Essence
Being what it is (essentia) must be conceived in terms of Being (existence) [Heidegger]
     Full Idea: Dasein's Being-what-it-is (essentia) must….be conceived in terms of its Being (existentia).
     From: Martin Heidegger (Being and Time [1927], 67/42), quoted by Richard Polt - Heidegger: an introduction 3.§2
     A reaction: This seems to be the origin of Sartre's famous slogan 'existence before essence'. It seems to be a rebellion against Husserl's quest for essences.
23. Ethics / F. Existentialism / 6. Authentic Self
Heidegger says we must either choose an inauthentic hero, or choose yourself as hero [Heidegger, by Critchley]
     Full Idea: Heidegger says you must choose your hero; either you choose 'das Man', the inauthentic life, or you choose yourself - the point being that you have to choose yourself as your hero in order to be authentic.
     From: report of Martin Heidegger (Being and Time [1927]) by Simon Critchley - Impossible Objects: interviews 5
     A reaction: If Nietzsche's 'Ecce Homo' is the model for choosing yourself as hero, I am not too sure about this idea. Needing a hero seems awfully German and romantic. Ein Heldenleben. Be your own anit-hero (like a standup comedian)?
26. Natural Theory / A. Speculations on Nature / 5. Infinite in Nature
Archelaus was the first person to say that the universe is boundless [Archelaus, by Diog. Laertius]
     Full Idea: Archelaus was the first person to say that the universe is boundless.
     From: report of Archelaus (fragments/reports [c.450 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.Ar.3
27. Natural Reality / G. Biology / 3. Evolution
Archelaus said life began in a primeval slime [Archelaus, by Schofield]
     Full Idea: Archelaus wrote that life on Earth began in a primeval slime.
     From: report of Archelaus (fragments/reports [c.450 BCE]) by Malcolm Schofield - Archelaus
     A reaction: This sounds like a fairly clearcut assertion of the production of life by evolution. Darwin's contribution was to propose the mechanism for achieving it. We should honour the name of Archelaus for this idea.