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Ideas of David J.Chalmers, by Text

[Australian, b.1966, Taught at the University of Indiana. Professor at Australian National University.]

1996 The Conscious Mind
p.7 Phenomenal consciousness is fundamental, with no possible nonphenomenal explanation
     Full Idea: In Chalmers's non-reductive theory, phenomenal consciousness is treated as a fundamental feature of the world, that cannot be explained in nonphenomenal terms. Theory is still possible, in the regularities of interaction.
     From: report of David J.Chalmers (The Conscious Mind [1996]) by U Kriegel / K Williford - Intro to 'Self-Representational Consciousness' n2
     A reaction: I can't make much sense of this view without a backing of panpsychism. How could a 'fundamental' feature of reality only begin to appear when life evolves on one particular planet? But 'panpsychism' is a warning of big misunderstandings. See Idea 2424.
p.21 Rationalist 2D semantics posits necessary relations between meaning, apriority, and possibility
     Full Idea: Chalmers seeks a rationalist interpretation of the 2D framework, situated in the tradition which posits a golden triangle of necessary constitutive relations between meaning, apriority, and possibility.
     From: report of David J.Chalmers (The Conscious Mind [1996]) by Laura Schroeter - Two-Dimensional Semantics 2.3.1
     A reaction: The first prize of the project is to get some sort of apriori knowledge about these crucial relations. I suppose the superduper prize is to get apriori knowledge of the possibilities of the world, but I wouldn't hold your breath waiting for that.
Intro p.-7 Hard Problem: why brains experience things
     Full Idea: The Hard Problem is: why is all this brain processing accompanied by an experienced inner life?
     From: David J.Chalmers (The Conscious Mind [1996], Intro)
     A reaction: The word 'accompanied' is interesting. A very epiphenomenal word! The answer to this neo-dualist question may be: if you do enough complex representational brain processing at high speed, it adds up to some which we call 'experience'.
1.1.3 p.17 Sometimes we don't notice our pains
     Full Idea: What of the fact that we speak of pains that last for a day, even though there are times that they are not conscious?
     From: David J.Chalmers (The Conscious Mind [1996], 1.1.3)
     A reaction: This is hardly proof that there are non-conscious pains. Otherwise we might say we have a pain even after it has left us for good (because it might return), which seems daft. Not a crucial issue. The word 'pain' has two uses…
1.1.3 p.19 We attribute beliefs to people in order to explain their behaviour
     Full Idea: Belief is something of an explanatory construct: we attribute beliefs to others largely in order to explain their behaviour.
     From: David J.Chalmers (The Conscious Mind [1996], 1.1.3)
1.1.5 p.28 Can we be aware but not conscious?
     Full Idea: Consciousness is always accompanied by awareness, but awareness as I have described it need not be accompanied by consciousness.
     From: David J.Chalmers (The Conscious Mind [1996], 1.1.5)
     A reaction: One should consult Chalmers, but he is stretching the English word 'awareness' rather far. This road leads to saying that thermostats are 'aware', and information is aware of its content, which is probably very wrong indeed. Compare Idea 2415.
1.2.1 p.33 Properties supervene if you can't have one without the other
     Full Idea: B-properties supervene on A-properties if no two possible situations are identical with respect to their A-properties while differing in their B-properties.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.1)
     A reaction: Personally I would have thought that if this condition is achieved, then we could go on to say B-properties supervene on A because A is causing them. We shouldn't be shy about this. Personally I think the Bs are necessary.
1.2.1 p.35 Logical supervenience is when one set of properties must be accompanied by another set
     Full Idea: B-properties logically supervene on A-properties if no two logically possible situations are identical with respect to their A-properties but distinct with respect to their B-properties.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.1)
     A reaction: This is the gap into which Chalmers wants to slip zombies. He's wrong. He thinks that because he can imagine Bs without As, that this makes their separation logically possible. No doubt he can imagine a bonfire on the moon.
1.2.1 p.36 Natural supervenience is when one set of properties is always accompanied by another set
     Full Idea: B-properties supervene naturally on A-properties if any two naturally possible situations with the same A-properties have the same B-properties.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.1)
     A reaction: Since it is hard to imagine a healthy working brain failing to produce consciousness, given the current laws of nature, almost everyone (except extreme dualists) must concede that they are naturally supervenient. I wonder why they are.
1.2.1 p.38 Zombies imply natural but not logical supervenience
     Full Idea: It seems logically possible that a creature physically identical to a conscious creature might have no conscious experiences (a zombie)…so conscious experience supervenes naturally but not logically on the physical.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.1)
     A reaction: "It seems possible" isn't much of an argument. This claim by Chalmers has been a great incentive to reassess what is or isn't possible. Can a brain lack consciousness? Can a tree fall over silently? Can cyanide stop poisoning us?
1.2.2 p.43 Reductive explanation is not the be-all and the end-all of explanation
     Full Idea: Reductive explanation is not the be-all and the end-all of explanation.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.2)
1.2.2 p.45 'Perception' means either an action or a mental state
     Full Idea: 'Perception' can be used to refer either to the act of perceiving, or the internal state that arises as a result.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.2)
1.2.3 p.48 Reduction requires logical supervenience
     Full Idea: Reductive explanation requires a logical supervenience relation.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.3)
     A reaction: Why can't you say that in another world there are zombies, but in this world the mind is explained by its natural supervenience on the brain (given the current natural laws)? Driving on the left in Britain is explained by current laws.
1.2.4 p.56 Kripke is often taken to be challenging a priori insights into necessity
     Full Idea: At various points in this book, I use a priori methods to gain insight into necessity; this is the sort of thing that Kripke's account is often taken to challenge.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.4)
     A reaction: Chalmers uses his 2-D approach to split off an a priori part from Kripke's a posterior part of our insight into necessity.
1.2.4 p.57 The 'primary intension' is non-empirical, and fixes extensions based on the actual-world reference
     Full Idea: The 'primary intension' of a concept is a function from worlds to extensions reflecting the way the actual-world reference is fixed, ...which is independent of empirical factors.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.4)
     A reaction: This bit is a priori because the concept picks out something, no matter what its essence turns out to be. I take it to be a priori because it is stipulative.
1.2.4 p.59 The 'secondary intension' is determined by rigidifying (as H2O) the 'water' picked out in the actual world
     Full Idea: The 'secondary intension' of 'water' picks out the water (H2O) in all worlds. ..It is determined by first evaluating the primary intension at the actual world, and then rigidifying it so that the same sort of thing is picked out in all possible worlds.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.4)
     A reaction: No wonder Soames calls 2-D semantics 'Byzantine'. If we don't actually do this psychologically, what exactly is Chalmers describing? Is this revisionary semantics - i.e. how we ought to do it if we want to talk about the world properly?
1.2.4 p.59 Meaning has split into primary ("watery stuff"), and secondary counterfactual meaning ("H2O")
     Full Idea: The single Fregean intension has fragmented into two: a primary intension ("watery stuff") that fixes reference in the actual world, and a secondary intension ("H2O") that picks out reference in counterfactual possible worlds.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.4)
     A reaction: No one actually performs this schizoid double operation, so this is theory disconnected from life. What is the role of 'H2O' in the actual world, and 'watery stuff' in the others?
1.2.4 p.60 Primary and secondary intensions are the a priori (actual) and a posteriori (counterfactual) aspects of meaning
     Full Idea: Primary intension picks out a referent in a world considered as actual; secondary considers it as counterfactual. ...(62) We can think of the primary and secondary intensions as the a priori and a posteriori aspects of meaning, respectively.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.4)
     A reaction: Primary intension is a priori because, it seems, it is stipulative ('water' means 'the watery stuff'), whereas the secondary intension (in counterfactual worlds) is empirical ('water' is used to refer to H2O/XYZ). We get internalism and externalism.
1.2.4 p.62 In two-dimensional semantics we have two aspects to truth in virtue of meaning
     Full Idea: Both the 'primary' and 'secondary' intension qualify as truths in virtue of meaning; they are simply true in virtue of different aspects of meaning.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.4)
     A reaction: This is the view of two-dimensional semantics, which has split Fregean sense into an a priori and an a posterior part. Chalmers is trying to hang onto the idea that we might see necessity as largely analytic.
1.2.4 p.63 Two-dimensional semantics gives a 'primary' and 'secondary' proposition for each statement
     Full Idea: If we see a proposition as a function from possible worlds to truth-values, then the two sets of truth-conditions yield two propositions associated with any statement. A 'primary' for those which express a truth, and 'secondary' for counterfactual truth.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.4)
     A reaction: This is where 2-D semantics becomes increasingly 'Byzantine'. Intuition and introspection don't seem to offer me two different propositions for every sentence I utter. I can't see this theory catching on, even if it is technically beautiful.
1.2.4 p.63 We have 'primary' truth-conditions for the actual world, and derived 'secondary' ones for counterfactual worlds
     Full Idea: 'Primary' truth-conditions tell us how the actual world has to be for an utterance of the statement to be true in that world; ....'secondary' truth-conditions give the truth-value in counterfactual worlds, given that the actual world turned out some way.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.4)
     A reaction: This is the reinterpretation of the truth-conditions account in terms of two-dimensional semantics. My first reaction is not very positive. Why can't we fix our references in counterfactual worlds, and then apply them to the actual (like inventions)?
1.2.4 p.68 Maybe logical possibility does imply conceivability - by an ideal mind
     Full Idea: If we understand conceivability as conceivability-in-principle (by a superbeing?) then it is plausible that logical possibility of a world implies conceivability of the world, so logical possibility of a statement implies its conceivability.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.4)
     A reaction: I see nothing incoherent in the possibility that there might be aspects of existence which are utterly inconceivable to any conscious mind. Infinity might be a start, if an 'infinite' mind were impossible.
1.2.5 p.82 Is intentionality just causal connections?
     Full Idea: Intentional properties should be analyzable in terms of causal connections to behaviour and the environment….so there is no separate ontological problem of intentionality.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.5)
     A reaction: There could only be no ontological problem if intentional states were purely physical. Everything is made of something (I presume).
1.2.5 p.85 Indexicals may not be objective, but they are a fact about the world as I see it
     Full Idea: Even if the indexical is not an objective fact about the world, it is a fact about the world as I find it, and it is the world as I find it that needs explanation.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.5)
     A reaction: Chalmers treats them as important, whereas the way he expresses it could make them eliminable, if the world seen by him is eliminable.
1.2.5 p.87 All facts are either physical, experiential, laws of nature, second-order final facts, or indexical facts about me
     Full Idea: Facts about the world are exhausted by physical facts, conscious experiences, laws of nature, a second-order that's-all fact, and perhaps an indexical fact about my location.
     From: David J.Chalmers (The Conscious Mind [1996], 1.2.5)
2.1 p.31 Physicalism says in any two physically indiscernible worlds the positive facts are the same
     Full Idea: Chalmers says that physicalism is true in a world w just in case every positive fact that obtains in w also obtains in any world physically indiscernible from w.
     From: report of David J.Chalmers (The Conscious Mind [1996], 2.1) by Karen Bennett - Supervenience
     A reaction: [Bennett summarises Chalmers' argument on pp.39-40] Chalmers says negative facts depend on the world's limits, which aren't part of the physical facts of the world. p.100 It seems possible to invert qualia
     Full Idea: It seems entirely coherent that experiences could be inverted while physical structure is duplicated exactly.
     From: David J.Chalmers (The Conscious Mind [1996],
     A reaction: Strange how what seems 'entirely coherent' to a leading philosopher strikes me as totally incoherent. I would have thought it was only coherent to a dualist. I don't believe God makes the physics on Thursday, and adds experiences on Friday. p.101 Nothing in physics even suggests consciousness
     Full Idea: Even if we knew every last detail about the physics of the universe, that information would not lead us to postulate the existence of conscious experience.
     From: David J.Chalmers (The Conscious Mind [1996],
     A reaction: I find this a very strange claim. Given that the biggest gap in our physical knowledge is that concerning the brain and consciousness, Chalmer is no position to say this. Why shouldn't a physical revelation suddenly make consciousness inevitable? p.103 Nothing external shows whether a mouse is conscious
     Full Idea: It is consistent with the physical facts about a mouse that it has conscious experiences, and it is consistent with the physical facts that it does not.
     From: David J.Chalmers (The Conscious Mind [1996],
     A reaction: No. It is consistent with our KNOWLEDGE of a mouse that it may or may not be conscious. I take this to be the key error of Chalmers, which led him to the mistaken idea that zombies are possible. The usual confusion of ontology and epistemology….
2.4.1 p.125 Perhaps consciousness is physically based, but not logically required by that base
     Full Idea: It remains plausible that consciousness arises from a physical basis, even though it is not entailed by that basis.
     From: David J.Chalmers (The Conscious Mind [1996], 2.4.1)
     A reaction: Personally I find this totally implausible. Since every other property or process in the known universe seems to be entailed by its physical basis, I don't expect the mind to be an exception.
2.4.1 p.130 H2O causes liquidity, but no one is a dualist about that
     Full Idea: Searle argues that H2O causes liquidity, but no one is a dualist about liquidity.
     From: David J.Chalmers (The Conscious Mind [1996], 2.4.1)
     A reaction: Good!
2.4.1 p.130 One can wrongly imagine two things being non-identical even though they are the same (morning/evening star)
     Full Idea: Just because one can imagine that A and B are not identical, it does not follow that A and B are not identical (think of the morning star and the evening star).
     From: David J.Chalmers (The Conscious Mind [1996], 2.4.1)
2.4.2 p.137 Metaphysical necessity is a bizarre, brute and inexplicable constraint on possibilities
     Full Idea: Strong metaphysical necessities will put constraints on the space of possible worlds that are brute and inexplicable. That's fine for our world, but bizarre for possible worlds. The realm of the possible has no room for such arbitrary constraint.
     From: David J.Chalmers (The Conscious Mind [1996], 2.4.2)
     A reaction: He would say this, given that he wants zombies to be possible, just because he thinks he can conceive of them. Presumably he thinks a raging bonfire with no flames is also possible. His objection here is weak.
2.4.2 p.137 Strong metaphysical necessity allows fewer possible worlds than logical necessity
     Full Idea: The hypothesized modality of 'strong' metaphysical necessity says there are fewer metaphysically possible worlds than there are logically possible worlds, and the a posteriori necessities can stem from factors independent of the semantics of terms.
     From: David J.Chalmers (The Conscious Mind [1996], 2.4.2)
     A reaction: Chalmers sets this up in order to reject it. He notes that it involves a big gap between conceivability and possibility. If a world is logically possible but metaphysically impossible, then it is impossible, surely?
2.4.2 p.137 How can we know the metaphysical impossibilities; the a posteriori only concerns this world
     Full Idea: If some worlds are metaphysically impossible, it seems that we could never know it. By assumption the information is not available a priori, and a posteriori information only tells us about our world.
     From: David J.Chalmers (The Conscious Mind [1996], 2.4.2)
     A reaction: You need essentialism to reply to this. If you discover the essence of something, you can predict its possibilities. You discover the natures of the powers and dispositions of actuality.
2.4.2 p.138 Presumably God can do anything which is logically possible
     Full Idea: Presumably it is in God's powers, when creating the world, to do anything that is logically possible.
     From: David J.Chalmers (The Conscious Mind [1996], 2.4.2)
     A reaction: I don't really understand why anyone would say that the only constraint on God is logic. Presumably no logic is breached if God places in object simultaneously in two spacetime locations, but it would be an impressive achievement.
2.4.4 p.156 Maybe dualist interaction is possible at the quantum level?
     Full Idea: The only form of interactionist dualism that has seemed even remotely tenable in the contemporary picture is one that exploits certain properties of quantum mechanics.
     From: David J.Chalmers (The Conscious Mind [1996], 2.4.4)
     A reaction: I think he is bluffing. No doubt quantum mechanics offers many intriguing possibilities, such as the interaction of many worlds within the mind, but I am not aware that anything non-physical is ever postulated. Physicists don't deal in the non-physical.
2.4.6 p.170 Supervenience makes interaction laws possible
     Full Idea: There is an objection to dualism that it cannot explain how the physical and the nonphysical interact, but the answer is simple on a natural supervenience framework - they interact by virtue of psychophysical laws (…which are as eternal as physics).
     From: David J.Chalmers (The Conscious Mind [1996], 2.4.6)
     A reaction: There are different sorts of laws. What Chalmers is hoping for would be a mere regularity, like the connection of cancer to smoking, but the objection is that the discovery of causal mechanisms, to give truly explanatory laws, is simply impossible.
2.5.2 p.177 Can we explain behaviour without consciousness?
     Full Idea: However the metaphysics of causation turns out, it seems relatively straightforward that a physical explanation of behaviour can be given that neither appeals to nor implies the existence of consciousness.
     From: David J.Chalmers (The Conscious Mind [1996], 2.5.2)
     A reaction: Chalmers needs this to support his idea that zombies are possible, but it strikes me as implausible. I find it inconceivable that our behaviour would be unchanged if we retained 'awareness' but lost consciousness. Try visiting an art gallery.
2.5.2 p.180 If I can have a zombie twin, my own behaviour doesn't need consciousness
     Full Idea: The explanation of my zombie twin's claims does not depend on consciousness, as there is none in his world. It follows that the explanation of my claims is also independent of the existence of consciousness.
     From: David J.Chalmers (The Conscious Mind [1996], 2.5.2)
     A reaction: Epiphenomenalism says my accounts of my consciousness are NOT because of my consciousness (which seems daft). Chalmers here gives a very good reason why we should not be a friend of philosophical zombies.
2.5.5 p.197 When distracted we can totally misjudge our own experiences
     Full Idea: If one is distracted one may make judgements about one's experiences that are quite false.
     From: David J.Chalmers (The Conscious Mind [1996], 2.5.5)
     A reaction: Of course, when one is distracted one can make mistakes about anything. This does imply that if there is indeed infallible knowledge to be had from introspection, it will at least require full concentration to achieve it. Cf Idea 8883.
3.6.3 p.227 In blindsight both qualia and intentionality are missing
     Full Idea: In blindsight, the information does not qualify as directly available for global control, and subjects are not truly aware of the information. The lack of experience corresponds directly to a lack of awareness.
     From: David J.Chalmers (The Conscious Mind [1996], 3.6.3)
     A reaction: Blindsight patients give correct answers about objects in their visual field, and you need 'global control' to speak the truth, even if you lack confidence in what you are saying. Philosophers should not be frightened of blindsight. Cf Idea 2391.
3.6.5 p.244 What turns awareness into consciousness?
     Full Idea: Given the necessity of awareness, any candidate for an underlying law will have the form "Awareness plus something gives rise to consciousness" (…but simplicity suggests leaving out the 'something').
     From: David J.Chalmers (The Conscious Mind [1996], 3.6.5)
     A reaction: You can't leave out the 'something' if you think awareness without consciousness is possible. The phenomenon of blindsight suggests that a whole extra brain area must come into play to produce the consciousness. It may not have a distinct ontology.
3.7.1 p.248 Does consciousness arise from fine-grained non-reductive functional organisation?
     Full Idea: I claim that conscious experience arises from fine-grained functional organisation….. we might call it 'non-reductive functionalism'.
     From: David J.Chalmers (The Conscious Mind [1996], 3.7.1)
     A reaction: This is Chalmers' final position. If consciousness is 'emergent' and cannot be reduced, what has fine-grained got to do with it? I take 'fine-grained' to be a hint at why the brain becomes conscious. Fine-grained functions cause something.
3.7.2 p.251 The Chinese Mind doesn't seem conscious, but then nor do brains from outside
     Full Idea: While it may be intuitively implausible that Block's 'mind' made of the population of China would give rise to conscious experience, it is equally intuitively implausible that a brain should give rise to experience.
     From: David J.Chalmers (The Conscious Mind [1996], 3.7.2)
     A reaction: This sounds like good support for functionalism, but I am more inclined to see it as a critique of 'intuition' as a route to truth where minds are concerned. Intuition isn't designed for that sort of work.
3.7.3 p.259 Why should qualia fade during silicon replacement?
     Full Idea: If parts of the brain are gradually replaced, perhaps by silicon chips, ...the most reasonable hypothesis is that qualia do not fade at all.
     From: David J.Chalmers (The Conscious Mind [1996], 3.7.3)
     A reaction: As it stands this could either assert dualism or functionalism. Personally I think the most reasonable hypothesis is that qualia would fade. Chalmers needs more imagination (or less?). What is it like to experience Alzheimer's Disease?
3.8.3 p.289 The structure of the retina has already simplified the colour information which hits it
     Full Idea: In vision three varieties of cones abstract out information according to the amount of light present in various overlapping wavelength ranges. Immediately, many distinctions present in the original light wave are lost.
     From: David J.Chalmers (The Conscious Mind [1996], 3.8.3)
3.8.4 p.295 Going down the scale, where would consciousness vanish?
     Full Idea: Moving down the scale from lizards to slugs, there doesn't seem much reason to suppose that phenomenology should wink out while a reasonably complex perceptual psychology persists….and if you move on down to thermostats, where would it wink out?
     From: David J.Chalmers (The Conscious Mind [1996], 3.8.4)
     A reaction: This doesn't seem much of an argument, particularly if its conclusion is that there is phenomenology in thermostats. When day changes into night, where does it 'wink out'? Are we to conclude that night doesn't exist, or that day doesn't exist?
3.8.4 p.297 It is odd if experience is a very recent development
     Full Idea: It would be odd for a fundamental property like experience to be instantiated for the first time only relatively late in the history of the universe, and even then only in occasional complex systems.
     From: David J.Chalmers (The Conscious Mind [1996], 3.8.4)
     A reaction: The assumption of this remark is that experience is 'fundamental', which seems to claim that it is a separate ontological category. Maybe, but experience doesn't seem to be a thing. 'Process' seems a better term, and that is not a novelty in the universe.
3.8.5 p.306 Why are minds homogeneous and brains fine-grained?
     Full Idea: The 'grain problem' for materialism was raised by Sellars: how could an experience be identical with a vast collection of physiological events, given the homogeneity of the former, and the fine-grainedness of the latter?
     From: David J.Chalmers (The Conscious Mind [1996], 3.8.5)
     A reaction: An interesting question, but it doesn't sound like a huge problem, given the number of connections in the brain. If the brain were expanded (as Leibniz suggested), the 'grains' might start to appear. We can't propose a 'deceived homunculus' to solve it.
4.9.4 p.323 Maybe the whole Chinese Room understands Chinese, though the person doesn't
     Full Idea: Opponents typically reply to Searle's argument by conceding that the person in the room does not understand Chinese, and arguing that the understanding should instead be attributed to the system consisting of the person and the pieces of paper.
     From: David J.Chalmers (The Conscious Mind [1996], 4.9.4)
     A reaction: Searle himself spotted this reply. It seems plausible to say that a book contains 'understanding', so the translation dictionary may have it. A good Room would cope with surprise questions.
n 2.20 p.364 Temperature (etc.) is agreed to be reducible, but it is multiply realisable
     Full Idea: Many physical phenomena that are often taken to be paradigms of reducibility (e.g. temperature) are in fact multiply realizable.
     From: David J.Chalmers (The Conscious Mind [1996], n 2.20)
     A reaction: So multiple realisability isn't such a big problem for physicalism. I take it, though, that all hot things have some physical type of event in common (a level of molecular energy). Finding the level of commonality is the challenge.
2002 Does Conceivability Entail Possibility?
p.129 Modal Rationalism: conceivability gives a priori access to modal truths
     Full Idea: Chalmers' 'modal rationalist' is one who identifies what is possible with what is conceivable; the central claim of the doctrine is that we have a priori access to modal truth.
     From: report of David J.Chalmers (Does Conceivability Entail Possibility? [2002]) by Robert C. Stalnaker - Mere Possibilities 5
     A reaction: A helpful clarification, as I can now see how hopelessly and utterly wrong Chalmers is (about almost everything), and I find my confidence in any sort of genuine a priori knowledge (except of conceptual relations) dwindling by the minute.
p.813 Evaluate primary possibility from some world, and secondary possibility from this world
     Full Idea: For Chalmers, that water is XYZ is 'primary possible' (a priori, or conceptually), because it is true in some world considered as actual. It is 'secondary impossible', when it is evaluated from the Earth as actual.
     From: report of David J.Chalmers (Does Conceivability Entail Possibility? [2002]) by Anand Vaidya - Understanding and Essence Intro
     A reaction: [compressed] This is Chalmers' account of how we can know possibility from conceivability, via his two-dimensional semantics (see alphabetical themes).
2004 Epistemic Two-Dimensional Semantics
p.165 p.24 A sentence is a priori if no possible way the world might actually be could make it false
     Full Idea: The Core Thesis for rationalist 2D semantics is that for any sentence S, S is apriori iff S has a necessary 1-intension. (That is, there is no possible way the world might be that, if it actually obtained, would make S false).
     From: David J.Chalmers (Epistemic Two-Dimensional Semantics [2004], p.165), quoted by Laura Schroeter - Two-Dimensional Semantics 2.3.2
     A reaction: [The parenthesis is by Schroeter] A '1-intension' is defined by a diagonal on a 2D semantic matrix. Chalmers defends conceivability as the guide to possibility. This is a very traditional view of the a priori, expressed in modern terms.
p.180-4 p.25 Truth in a scenario is the negation with that scenario being a priori incoherent
     Full Idea: The epistemic 1-intension for a sentence S is True at a scenario W iff (W and not-S) is a priori incoherent.
     From: David J.Chalmers (Epistemic Two-Dimensional Semantics [2004], p.180-4), quoted by Laura Schroeter - Two-Dimensional Semantics
     A reaction: See Two-Dimensional Semantics (in 'Language') and Chalmers for the background to this idea. I love the coherence view of justification, but get a bit nervous when people start defining truth in that way.
2006 Foundations of Two-Dimensional Semantics
p.108 'Water' is two-dimensionally inconstant, with different intensions in different worlds
     Full Idea: For Chalmers, 'water' is two-dimensionally inconstant, in that it has different secondary intensions relative to different worlds of utterance.
     From: report of David J.Chalmers (Foundations of Two-Dimensional Semantics [2006]) by Theodore Sider - Four Dimensionalism 7.2
     A reaction: In this way 'water' is regarded as being like an indexical (such as 'I'), which has a fixed meaning component, and a second component which varies with different utterances. Maybe.