18 ideas
| 18487 | We want to know what makes sentences true, rather than defining 'true' [McFetridge] |
| Full Idea: The generalisation 'What makes a (any) sentence true?' is not a request for definitions of 'true' (the concept), but rather requests for (partial) explanations of why certain particular sentences are true. | |
| From: Ian McFetridge (Truth, Correspondence, Explanation and Knowledge [1977], II) | |
| A reaction: McFetridge is responding to the shortcomings of Tarski's account of truth. The mystery seems to be why some of our representations of the world are 'successful', and others are not. |
| 14235 | Saying 'they can become a set' is a tautology, because reference to 'they' implies a collection [Cargile] |
| Full Idea: If the rule is asserted 'Given any well-determined objects, they can be collected into a set by an application of the 'set of' operation', then on the usual account of 'they' this is a tautology. Collection comes automatically with this form of reference. | |
| From: James Cargile (Paradoxes: Form and Predication [1979], p.115), quoted by Oliver,A/Smiley,T - What are Sets and What are they For? Intro | |
| A reaction: Is this a problem? Given they are well-determined (presumably implying countable) there just is a set of them. That's what set theory is, I thought. Of course, the iterative view talks of 'constructing' the sets, but the construction looks unstoppable. |
| 18488 | We normally explain natural events by citing further facts [McFetridge] |
| Full Idea: If one were asked 'What makes salt soluble in water?', the most natural answer would be something of the style 'The fact that it has such-and-such structure'. | |
| From: Ian McFetridge (Truth, Correspondence, Explanation and Knowledge [1977], II) | |
| A reaction: Personally I would want to talk about its 'powers' (dispositional properties), rather than its 'structure' (categorical properties). This defends facts, but you could easily paraphrase 'fact' out of this reply (as McFetridge realised). |
| 12184 | Logical necessity overrules all other necessities [McFetridge] |
| Full Idea: If it is logically necessary that if p then q, then there is no other sense of 'necessary' in which it is not necessary that if p then q. | |
| From: Ian McFetridge (Logical Necessity: Some Issues [1986], §1) | |
| A reaction: The thesis which McFetridge proposes to defend. The obvious rival would be metaphysical necessity, and the rival claim would presumably be that things are only logically necessary if that is entailed by a metaphysical necessity. Metaphysics drives logic. |
| 15083 | The fundamental case of logical necessity is the valid conclusion of an inference [McFetridge, by Hale] |
| Full Idea: McFetridge's conception of logical necessity is one which sees the concept as receiving its fundamental exemplification in the connection between the premiss and conclusion of a deductively valid inference. | |
| From: report of Ian McFetridge (Logical Necessity: Some Issues [1986]) by Bob Hale - Absolute Necessities 2 | |
| A reaction: This would mean that p could be logically necessary but false (if it was a valid argument from false premisses). What if it was a valid inference in a dodgy logical system (including 'tonk', for example)? |
| 15084 | In the McFetridge view, logical necessity means a consequent must be true if the antecedent is [McFetridge, by Hale] |
| Full Idea: McFetridge's view proves that if the conditional corresponding to a valid inference is logically necessary, then there is no sense in which it is possible that its antecedent be true but its consequent false. ..This result generalises to any statement. | |
| From: report of Ian McFetridge (Logical Necessity: Some Issues [1986]) by Bob Hale - Absolute Necessities 2 | |
| A reaction: I am becoming puzzled by Hale's assertion that logical necessity is 'absolute', while resting his case on a conditional. Are we interested in the necessity of the inference, or the necessity of the consequent? |
| 12180 | Logical necessity requires that a valid argument be necessary [McFetridge] |
| Full Idea: There will be a legitimate notion of 'logical' necessity only if there is a notion of necessity which attaches to the claim, concerning a deductively valid argument, that if the premisses are true then so is the conclusion. | |
| From: Ian McFetridge (Logical Necessity: Some Issues [1986], §1) | |
| A reaction: He quotes Aristotle's Idea 11148 in support. Is this resting a stronger idea on a weaker one? Or is it the wrong way round? We endorse validity because we see the necessity; we don't endorse necessity because we see 'validity'. |
| 12181 | Traditionally, logical necessity is the strongest, and entails any other necessities [McFetridge] |
| Full Idea: The traditional crucial assumption is that logical necessity is the strongest notion of necessity. If it is logically necessary that p, then it is necessary that p in any other use of the notion of necessity there may be (physically, practically etc.). | |
| From: Ian McFetridge (Logical Necessity: Some Issues [1986], §1) | |
| A reaction: Sounds right. We might say it is physically necessary simply because it is logically necessary, and even that it is metaphysically necessary because it is logically necessary (required by logic). Logical possibility is hence the weakest kind? |
| 12183 | It is only logical necessity if there is absolutely no sense in which it could be false [McFetridge] |
| Full Idea: Is there any sense in which, despite an ascription of necessity to p, it is held that not-p is possible? If there is, then the original claim then it was necessary is not a claim of 'logical' necessity (which is the strongest necessity). | |
| From: Ian McFetridge (Logical Necessity: Some Issues [1986], §1) | |
| A reaction: See Idea 12181, which leads up to this proposed "test" for logical necessity. McFetridge has already put epistemic ('for all I know') possibility to one side. □p→¬◊¬p is the standard reading of necessity. His word 'sense' bears the burden. |
| 12192 | The mark of logical necessity is deduction from any suppositions whatever [McFetridge] |
| Full Idea: The manifestation of the belief that a mode of inference is logically necessarily truth-preserving is the preparedness to employ that mode of inference in reasoning from any set of suppositions whatsoever. | |
| From: Ian McFetridge (Logical Necessity: Some Issues [1986], §4) | |
| A reaction: He rests this on the idea of 'cotenability' of the two sides of a counterfactual (in Mill, Goodman and Lewis). There seems, at first blush, to be a problem of the relevance of the presuppositions. |
| 12182 | We assert epistemic possibility without commitment to logical possibility [McFetridge] |
| Full Idea: Time- and person-relative epistemic possibility can be asserted even when logical possibility cannot, such as undecided mathematical propositions. 'It may be that p' just comes to 'For all I know, not-p'. | |
| From: Ian McFetridge (Logical Necessity: Some Issues [1986], §1) | |
| A reaction: If it is possible 'for all I know', then it could be actual for all I know, and if we accept that it might be actual, we could hardly deny that it is logically possible. Logical and epistemic possibilities of mathematical p stand or fall together. |
| 12187 | Objectual modal realists believe in possible worlds; non-objectual ones rest it on the actual world [McFetridge] |
| Full Idea: The 'objectual modal realist' holds that what makes modal beliefs true are certain modal objects, typically 'possible worlds'. ..The 'non-objectual modal realist' says modal judgements are made true by how things stand with respect to this world. | |
| From: Ian McFetridge (Logical Necessity: Some Issues [1986], §2) | |
| A reaction: I am an enthusiastic 'non-objectual modal realist'. I accept the argument that real possible worlds have no relevance to the actual world, and explain nothing (see Jubien). The possibilities reside in the 'powers' of this world. See Molnar on powers. |
| 12186 | Modal realists hold that necessities and possibilities are part of the totality of facts [McFetridge] |
| Full Idea: The 'modal realist' holds that part of the totality of what is the case, the totality of facts, are such things as that certain events could have happened, certain propositions are necessarily true, if this happened then that would have been the case. | |
| From: Ian McFetridge (Logical Necessity: Some Issues [1986], §2) | |
| A reaction: I am an enthusiastic modal realist. If the aim of philosophy is 'to understand' (and I take that to be the master idea of the subject) then no understanding is possible which excludes the possibilities and necessities in things. |
| 21275 | Unlike a stone, the parts of a watch are obviously assembled in order to show the time [Paley] |
| Full Idea: When we come to inspect a watch we perceive (what we could not discover in a stone) that its several parts are put together for a purpose, to produce motion, and that motion so regulated as to point out the hour of the day. | |
| From: William Paley (Natural Theology [1802], Ch 1) | |
| A reaction: Microscopic examination of the stone would have surprised Paley. Should we infer a geometer because the sun is spherical? Crytals look designed, but are explained by deeper chemistry. |
| 21276 | From the obvious purpose and structure of a watch we must infer that it was designed [Paley] |
| Full Idea: The inference is inevitable that the watch had a maker; that there must have existed, at some time, an artificer or artificers who formed it for the purpose which we find it actually to answer, who designed its use. | |
| From: William Paley (Natural Theology [1802], Ch 1) | |
| A reaction: It rather begs the question to refer to an ordered structure as a 'design'. Why do we think it is absurd to think the the 'purpose' of the sun is to benefit mankind? Suppose we found a freakish natural sundial in the woods. |
| 21277 | Even an imperfect machine can exhibit obvious design [Paley] |
| Full Idea: It is not necessary that a machine be perfect, in order to show with what design it was made. | |
| From: William Paley (Natural Theology [1802], Ch 1) | |
| A reaction: This encounters Hume's point that you will then have to infer that the designer contains similar imperfections. If you look at plagues, famines and mothers dying in childbirth (see Mill), you might wish the designer had never started. |
| 21278 | All the signs of design found in a watch are also found in nature [Paley] |
| Full Idea: Every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature. | |
| From: William Paley (Natural Theology [1802], Ch.3) | |
| A reaction: This is far from obvious. It was crucial to the watch analogy that we immediately see its one self-evident purpose. No one looks at nature and says 'Aha, I know what this is all for'. |
| 21357 | No organ shows purpose more obviously than the eyelid [Paley] |
| Full Idea: The eyelid defends the eye; it wipes it; it closes it in sleep. Are there, in any work of art whatever, purposes more evident than those which this organ fulfils? | |
| From: William Paley (Natural Theology [1802], p.24), quoted by Armand Marie LeRoi - The Lagoon: how Aristotle invented science 031 | |
| A reaction: Nice to have another example, in addition to the watch. He is not wholly wrong, because it is impossible to give an evolutionary account of the development of the eyelid without referring to some sort of teleological aspect. The eyelid has a function. |