32 ideas
| 5750 | Consistency is modal, saying propositions are consistent if they could be true together [Melia] |
| Full Idea: Consistency is a modal notion: a set of propositions is consistent iff all the members of the set could be true together. | |
| From: Joseph Melia (Modality [2003], Ch.6) | |
| A reaction: This shows why Kantian ethics, for example, needs a metaphysical underpinning. Maybe Kant should have believed in the reality of Leibnizian possible worlds? An account of reason requires an account of necessity and possibility. |
| 19504 | My modus ponens might be your modus tollens [Pritchard,D] |
| Full Idea: One philosopher's modus ponens is another philosopher's modus tollens. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], 3.§2) | |
| A reaction: [Anyone know the originator of this nice thought?] You say A is true, and A proves B, so B is true. I reply that if A proves something as daft as B, then so much the worse for A. Ain't it the truth? |
| 5737 | Predicate logic has connectives, quantifiers, variables, predicates, equality, names and brackets [Melia] |
| Full Idea: First-order predicate language has four connectives, two quantifiers, variables, predicates, equality, names, and brackets. | |
| From: Joseph Melia (Modality [2003], Ch.2) | |
| A reaction: Look up the reference for the details! The spirit of logic is seen in this basic framework, and the main interest is in the ontological commitment of the items on the list. The list is either known a priori, or it is merely conventional. |
| 5744 | First-order predicate calculus is extensional logic, but quantified modal logic is intensional (hence dubious) [Melia] |
| Full Idea: First-order predicate calculus is an extensional logic, while quantified modal logic is intensional (which has grave problems of interpretation, according to Quine). | |
| From: Joseph Melia (Modality [2003], Ch.3) | |
| A reaction: The battle is over ontology. Quine wants the ontology to stick with the values of the variables (i.e. the items in the real world that are quantified over in the extension). The rival view arises from attempts to explain necessity and counterfactuals. |
| 5740 | Second-order logic needs second-order variables and quantification into predicate position [Melia] |
| Full Idea: Permitting quantification into predicate position and adding second-order variables leads to second-order logic. | |
| From: Joseph Melia (Modality [2003], Ch.2) | |
| A reaction: Often expressed by saying that we now quantify over predicates and relations, rather than just objects. Depends on your metaphysical commitments. |
| 5741 | If every model that makes premises true also makes conclusion true, the argument is valid [Melia] |
| Full Idea: In first-order predicate calculus validity is defined thus: an argument is valid iff every model that makes the premises of the argument true also makes the conclusion of the argument true. | |
| From: Joseph Melia (Modality [2003], Ch.2) | |
| A reaction: See Melia Ch. 2 for an explanation of a 'model'. Traditional views of validity tend to say that if the premises are true the conclusion has to be true (necessarily), but this introduces the modal term 'necessarily', which is controversial. |
| 5735 | Maybe names and predicates can capture any fact [Melia] |
| Full Idea: Some philosophers think that any fact can be captured in a language containing only names and predicates. | |
| From: Joseph Melia (Modality [2003], Ch.2) | |
| A reaction: The problem case Melia is discussing is modal facts, such as 'x is possible'. It is hard to see how 'possible' could be an ordinary predicate, but then McGinn claims that 'existence' is, and that there are some predicates with unusual characters. |
| 5736 | No sort of plain language or levels of logic can express modal facts properly [Melia] |
| Full Idea: Some philosophers say that modal facts cannot be expressed either by name/predicate language, or by first-order predicate calculus, or even by second-order logic. | |
| From: Joseph Melia (Modality [2003], Ch.2) | |
| A reaction: If 'possible' were a predicate, none of this paraphernalia would be needed. If possible worlds are accepted, then the quantifiers of first-order predicate calculus will do the job. If neither of these will do, there seems to be a problem. |
| 5746 | The Identity of Indiscernibles is contentious for qualities, and trivial for non-qualities [Melia] |
| Full Idea: If the Identity of Indiscernibles is referring to qualitative properties, such as 'being red' or 'having mass', it is contentious; if it is referring to non-qualitative properties, such as 'member of set s' or 'brother of a', it is true but trivial. | |
| From: Joseph Melia (Modality [2003], Ch.3 n 11) | |
| A reaction: I would say 'false' rather than 'contentious'. No one has ever offered a way of distinguishing two electrons, but that doesn't mean there is just one (very busy) electron. The problem is that 'indiscernible' is only an epistemological concept. |
| 5738 | We may be sure that P is necessary, but is it necessarily necessary? [Melia] |
| Full Idea: We may have fairly firm beliefs as to whether or not P is necessary, but many of us find ourselves at a complete loss when wondering whether or not P is necessarily necessary. | |
| From: Joseph Melia (Modality [2003], Ch.2) | |
| A reaction: I think it is questions like this which are pushing philosophy back towards some sort of rationalism. See Idea 3651, for example. A regress of necessities would be mad, so necessity must be taken as self-evident (in itself, though maybe not to us). |
| 5732 | 'De re' modality is about things themselves, 'de dicto' modality is about propositions [Melia] |
| Full Idea: In cases of 'de re' modality, it is a particular thing that has the property essentially or accidentally; where the modality attaches to the proposition, it is 'de dicto' - it is the whole truth that all bachelors are unmarried that is necessary. | |
| From: Joseph Melia (Modality [2003], Ch.1) | |
| A reaction: This seems to me one of the most important distinctions in metaphysics (as practised by analytical philosophers, who like distinctions). The first type leads off into the ontology, the second type veers towards epistemology. |
| 5739 | Sometimes we want to specify in what ways a thing is possible [Melia] |
| Full Idea: Sometimes we want to count the ways in which something is possible, or say that there are many ways in which a certain thing is possible. | |
| From: Joseph Melia (Modality [2003], Ch.2) | |
| A reaction: This is a basic fact about talk of 'possibility'. It is not an all-or-nothing property of a situation. There can be 'faint' possibilities of things. The proximity of some possible worlds, especially those sharing our natural laws, is one answer. |
| 19503 | An improbable lottery win can occur in a nearby possible world [Pritchard,D] |
| Full Idea: Low probability events such as lottery wins can occur in nearby possible worlds. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], 2.n2) | |
| A reaction: This seems to ruin any chance of mapping probabilities and counterfactuals in the neat model of nested possible worlds (like an onion). [Lewis must have thought of this, surely? - postcards, please] |
| 5734 | Possible worlds make it possible to define necessity and counterfactuals without new primitives [Melia] |
| Full Idea: In modal logic the concepts of necessity and counterfactuals are not interdefinable, so the language needs two primitives to represent them, but with the machinery of possible worlds they are defined by what is the case in all worlds, or close worlds. | |
| From: Joseph Melia (Modality [2003], Ch.1) | |
| A reaction: If your motivation is to reduce ontology to the barest of minimums (which it was for David Lewis) then it is paradoxical that the existence of possible worlds may be the way to achieve it. I doubt, though, whether a commitment to their reality is needed. |
| 5742 | In possible worlds semantics the modal operators are treated as quantifiers [Melia] |
| Full Idea: The central idea in possible worlds semantics is that the modal operators are treated as quantifiers. | |
| From: Joseph Melia (Modality [2003], Ch.2) | |
| A reaction: It seems an essential requirement of metaphysics that an account be given of possibility and necessity, and it is also a good dream to keep the ontology simple. Commitment to possible worlds is the bizarre outcome of this dream. |
| 5743 | If possible worlds semantics is not realist about possible worlds, logic becomes merely formal [Melia] |
| Full Idea: It has proved difficult to justify possible worlds semantics without accepting possible worlds. Without a secure metaphysical underpinning, the results in logic are in danger of having nothing more than a formal significance. | |
| From: Joseph Melia (Modality [2003], Ch.2) | |
| A reaction: This makes nicely clear why Lewis's controversial modal realism has to be taken seriously. It appears that the key problem is truth, because that is needed to define validity, but you can't have truth without some sort of metaphysics. |
| 5749 | Possible worlds could be real as mathematics, propositions, properties, or like books [Melia] |
| Full Idea: One can be a realist about possible worlds without adopting Lewis's extreme views; they might be abstract or mathematical entities; they might be sets of propositions or maximal uninstantiated properties; they might be like books or pictures. | |
| From: Joseph Melia (Modality [2003], Ch.6) | |
| A reaction: My intuition is that once you go down the road of realism about possible worlds, Lewis's full concrete realism looks at least as attractive as any of these options. You can discuss the 'average man' in an economic theory without realism. |
| 5751 | The truth of propositions at possible worlds are implied by the world, just as in books [Melia] |
| Full Idea: Propositions are true at possible worlds in much the same way as they are true at books: by being implied by the book. | |
| From: Joseph Melia (Modality [2003], Ch.7) | |
| A reaction: An intriguing way to introduce the view that possible worlds should be seen as like books. The truth-makers of propositions about the actual world are items in it, but the truth-makers in novels (say) are the conditions of the whole work as united. |
| 19505 | Moore begs the question, or just offers another view, or uses 'know' wrongly [Pritchard,D, by PG] |
| Full Idea: The three main objections to Moore's common-sense refutation of scepticism is that it either begs the question, or it just offers a rival view instead of a refutation, or it uses 'know' in a conversationally inappropriate way. | |
| From: report of Duncan Pritchard (Epistemological Disjunctivism [2012], 3.§2) by PG - Db (ideas) | |
| A reaction: [I deserve applause for summarising two pages of Pritchard's wordy stuff so neatly] |
| 19499 | We can have evidence for seeing a zebra, but no evidence for what is entailed by that [Pritchard,D] |
| Full Idea: The closure principle forces us to regard Zula as knowing that what she is looking at is not a cleverly disguised mule, and yet she doesn't appear to have any supporting evidence for this knowledge. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], 2.§3) | |
| A reaction: [Zula observes a zebra in the zoo] Entailment is a different type of justification from perception. If we add fallibilism to the mix, then fallibility can increase as we pursue a string of entailments. But proper logic, of course, should not be fallible. |
| 19500 | Favouring: an entailment will give better support for the first belief than reason to deny the second [Pritchard,D] |
| Full Idea: The Favouring Principle says that if S knows two things, and that the first entails the second, then S has better evidence in support of her belief in the first than she has for denying the second. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], 2.§3) | |
| A reaction: [his version is full of Greek letters, but who wants that stuff?] Pritchard concludes that if you believe in the closure principle then you should deny the favouring principle. |
| 19502 | Maybe knowledge just needs relevant discriminations among contrasting cases [Pritchard,D] |
| Full Idea: According to the 'contrastivist' proposal knowledge is to be understood as essentially involving discrimination, such that knowing a proposition boils down to having the relevant discriminatory capacities. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], 2.§6) | |
| A reaction: Pritchard says this isn't enough, and we must also to be aware of supporting favouring evidence. I would focus on the concept of coherence, even for simple perceptual knowledge. If I see a hawk in England, that's fine. What if I 'see' a vulture? |
| 19498 | Epistemic internalism usually says justification must be accessible by reflection [Pritchard,D] |
| Full Idea: Typically, internal epistemic conditions are characterised in terms of a reflective access requirement. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], 1.§6) | |
| A reaction: If your justification is straightforwardly visual, it is unclear what the difference would be between seeing the thing and having reflective access to the seeing. |
| 19506 | Externalism is better than internalism in dealing with radical scepticism [Pritchard,D] |
| Full Idea: Standard epistemic internalism faces an uphill struggle when it comes to dealing with radical scepticism, which points in favour of epistemic externalist neo-Mooreanism. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], 3.§3) | |
| A reaction: I incline towards internalism. I deal with scepticism by being a fallibilist, and adding 'but you never know' to every knowledge claim, and then getting on with life. |
| 19496 | Disjunctivism says perceptual justification must be both factual and known by the agent [Pritchard,D] |
| Full Idea: Slogan for disjunctivism: perceptual knowledge is paradigmatically constituted by a true belief whose epistemic support is both factive (i.e. it entails the truth of the propositions believed) and reflectively accessible to the agent. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], Intro) | |
| A reaction: I'm not a fan of externalism, but it could be that the factive bit achieves the knowledge, and then being able to use and answer for that knowledge may just be a bonus, and not an essential ingredient. |
| 19497 | Metaphysical disjunctivism says normal perceptions and hallucinations are different experiences [Pritchard,D] |
| Full Idea: Metaphysical disjunctivists hold that veridical perceptual experiences are not essentially the same as the experiences involved in corresponding cases involving illusion and (especially) hallucination. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], 1.§4) | |
| A reaction: Metaphysical disjunctivism concerns what the experiences are; epistemological justification concerns the criteria of justification. I think. I wish Pritchard would spell things out more clearly. Indeed, I wish all philosophers would. |
| 19495 | Epistemic externalism struggles to capture the idea of epistemic responsibility [Pritchard,D] |
| Full Idea: A fundamental difficulty for epistemic externalist positions is that it is hard on this view to capture any adequate notion of epistemic responsibility. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], Intro) | |
| A reaction: He never explains the 'responsibility', but I presume that would be like an expert witness in court, vouching for their knowledge. |
| 19501 | We assess error against background knowledge, but that is just what radical scepticism challenges [Pritchard,D] |
| Full Idea: When faced with an error-possibility we can appeal to background knowledge, as long as the error-possibility does not call into question this background knowledge. The same is not true when we focus on the radical sceptical hypothesis. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], 2.§5) | |
| A reaction: [reworded] Doubting everything simultaneously just looks like a mad project. If you doubt linguistic meaning, you can't even express your doubts. |
| 19507 | Radical scepticism is merely raised, and is not a response to worrying evidence [Pritchard,D] |
| Full Idea: Crucially, radical sceptical error-possibilities are never epistemically motivated, but are instead merely raised. | |
| From: Duncan Pritchard (Epistemological Disjunctivism [2012], 3.§5) | |
| A reaction: In 'The Matrix' someone sees a glitch in the software (a cat crossing a passageway), and that would have to be taken seriously. Otherwise it is a nice strategy to ask why the sceptic is raising this bizzare possibility, without evidence. |
| 5748 | We accept unverifiable propositions because of simplicity, utility, explanation and plausibility [Melia] |
| Full Idea: Many philosophers now concede that it is rational to accept a proposition not because we can directly verify it but because it is supported by considerations of simplicity, theoretical utility, explanatory power and/or intuitive plausibility. | |
| From: Joseph Melia (Modality [2003], Ch.5) | |
| A reaction: This suggests how the weakness of logical positivism may have led us to the concept of epistemic virtues (such as those listed), which are, of course, largely a matter of community consensus, just as the moral virtues are. |
| 1748 | 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 |
| 5989 | 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. |