26 ideas
| 19215 | Arguers often turn the opponent's modus ponens into their own modus tollens [Merricks] |
| Full Idea: There is a seasoned method of turning your opponent's modus ponens into your own modus tollens. | |
| From: Trenton Merricks (Propositions [2015], 5.VII) | |
| A reaction: That is, they say 'if he's coming he'll be hear by now, and he's definitely coming', to which you say 'I'm afraid he's not here, so he obviously isn't coming after all'. They say if-A-then-B, and A, so B. You say not-B, so you're wrong about A. |
| 19205 | 'Snow is white' only contingently expresses the proposition that snow is white [Merricks] |
| Full Idea: It is contingently true that 'snow is white' expresses the proposition that snow is white. | |
| From: Trenton Merricks (Propositions [2015], 1.V n14) | |
| A reaction: Tarski stuck to sentences, but Merricks rightly argues that truth concerns propositions, not sentences. Sentences are subservient entities - mere tools used to express what matters, which is our thoughts (say I). |
| 19209 | Simple Quantified Modal Logc doesn't work, because the Converse Barcan is a theorem [Merricks] |
| Full Idea: Logical consequence guarantees preservation of truth. The Converse Barcan, a theorem of Simple Quantified Modal Logic, says that an obvious truth implies an obvious falsehood. So SQML gets logical consequence wrong. So SQML is mistaken. | |
| From: Trenton Merricks (Propositions [2015], 2.V) | |
| A reaction: I admire this. The Converse Barcan certainly strikes me as wrong (Idea 19208). Merricks grasps this nettle. Williamson grasps the other nettle. Most people duck the issue, I suspect. Merricks says later that domains are the problem. |
| 19208 | The Converse Barcan implies 'everything exists necessarily' is a consequence of 'necessarily, everything exists' [Merricks] |
| Full Idea: The Converse Barcan Formula has a startling result. Simple Quantified Modal Logic (SQML) has the following as a theorem: □∀xFx → ∀x□Fx. So 'everything exists necessarily' is a consequence of 'necessarily, everything exists'. | |
| From: Trenton Merricks (Propositions [2015], 2.V) | |
| A reaction: He says this is blatantly wrong. Williamson is famous for defending it. I think I'm with Merricks on this one. |
| 19207 | Sentence logic maps truth values; predicate logic maps objects and sets [Merricks] |
| Full Idea: The models for sentential logic map sentences to truth-values. The models for predicate logic map parts of sentences to objects and sets. | |
| From: Trenton Merricks (Propositions [2015], 2.II) | |
| A reaction: Logic books rarely tell you important things like this. That is why this database is so incredibly important! You will never understand the subject if you don't collect together the illuminating asides of discussion. They say it all so much more simply. |
| 13472 | Hilbert aimed to eliminate number from geometry [Hilbert, by Hart,WD] |
| Full Idea: One of Hilbert's aims in 'The Foundations of Geometry' was to eliminate number [as measure of lengths and angles] from geometry. | |
| From: report of David Hilbert (Foundations of Geometry [1899]) by William D. Hart - The Evolution of Logic 2 | |
| A reaction: Presumably this would particularly have to include the elimination of ratios (rather than actual specific lengths). |
| 9546 | Euclid axioms concerns possibilities of construction, but Hilbert's assert the existence of objects [Hilbert, by Chihara] |
| Full Idea: Hilbert's geometrical axioms were existential in character, asserting the existence of certain geometrical objects (points and lines). Euclid's postulates do not assert the existence of anything; they assert the possibility of certain constructions. | |
| From: report of David Hilbert (Foundations of Geometry [1899]) by Charles Chihara - A Structural Account of Mathematics 01.1 | |
| A reaction: Chihara says geometry was originally understood modally, but came to be understood existentially. It seems extraordinary to me that philosophers of mathematics can have become more platonist over the centuries. |
| 18742 | Hilbert's formalisation revealed implicit congruence axioms in Euclid [Hilbert, by Horsten/Pettigrew] |
| Full Idea: In his formal investigation of Euclidean geometry, Hilbert uncovered congruence axioms that implicitly played a role in Euclid's proofs but were not explicitly recognised. | |
| From: report of David Hilbert (Foundations of Geometry [1899]) by Horsten,L/Pettigrew,R - Mathematical Methods in Philosophy 2 | |
| A reaction: The writers are offering this as a good example of the benefits of a precise and formal approach to foundational questions. It's hard to disagree, but dispiriting if you need a PhD in maths before you can start doing philosophy. |
| 18217 | Hilbert's geometry is interesting because it captures Euclid without using real numbers [Hilbert, by Field,H] |
| Full Idea: Hilbert's formulation of the Euclidean theory is of special interest because (besides being rigorously axiomatised) it does not employ the real numbers in the axioms. | |
| From: report of David Hilbert (Foundations of Geometry [1899]) by Hartry Field - Science without Numbers 3 | |
| A reaction: Notice that this job was done by Hilbert, and not by the fictionalist Hartry Field. |
| 19214 | In twinning, one person has the same origin as another person [Merricks] |
| Full Idea: Origin essentialists claim that parental union results in a person, and that person could not have resulted from any other union. However, if the fertilised egg undergoes twinning, at least one of the resultant persons is not the original person. | |
| From: Trenton Merricks (Propositions [2015], 5.V) | |
| A reaction: Merricks says that therefore that origin could have just produced the second twin, rather than the original person. This is interesting, but doesn't seem to threaten the necessity of origin thesis. Once I'm here, I have that origin, despite my twin. |
| 7658 | Obviously there can't be a functional anaylsis of qualia if they are defined by intrinsic properties [Dennett] |
| Full Idea: If you define qualia as intrinsic properties of experiences considered in isolation from all their causes and effects, logically independent of all dispositional properties, then they are logically guaranteed to elude all broad functional analysis. | |
| From: Daniel C. Dennett (Sweet Dreams [2005], Ch.8) | |
| A reaction: This is a good point - it seems daft to reify qualia and imagine them dangling in mid-air with all their vibrant qualities - but that is a long way from saying there is nothing more to qualia than functional roles. Functions must be exlained too. |
| 7655 | The work done by the 'homunculus in the theatre' must be spread amongst non-conscious agencies [Dennett] |
| Full Idea: All the work done by the imagined homunculus in the Cartesian Theater must be distributed among various lesser agencies in the brain, none of which is conscious. | |
| From: Daniel C. Dennett (Sweet Dreams [2005], Ch.3) | |
| A reaction: Dennett's account crucially depends on consciousness being much more fragmentary than most philosophers claim it to be. It is actually full of joints, which can come apart. He may be right. |
| 7657 | Intelligent agents are composed of nested homunculi, of decreasing intelligence, ending in machines [Dennett] |
| Full Idea: As long as your homunculi are more stupid and ignorant than the intelligent agent they compose, the nesting of homunculi within homunculi can be finite, bottoming out, eventually, with agents so unimpressive they can be replaced by machines. | |
| From: Daniel C. Dennett (Sweet Dreams [2005], Ch.6) | |
| A reaction: [Dennett first proposed this in 'Brainstorms' 1978]. This view was developed well by Lycan. I rate it as one of the most illuminating ideas in the modern philosophy of mind. All complex systems (like aeroplanes) have this structure. |
| 7656 | I don't deny consciousness; it just isn't what people think it is [Dennett] |
| Full Idea: I don't maintain, of course, that human consciousness does not exist; I maintain that it is not what people often think it is. | |
| From: Daniel C. Dennett (Sweet Dreams [2005], Ch.3) | |
| A reaction: I consider Dennett to be as near as you can get to an eliminativist, but he is not stupid. As far as I can see, the modern philosopher's bogey-man, the true total eliminativist, simply doesn't exist. Eliminativists usually deny propositional attitudes. |
| 7654 | What matters about neuro-science is the discovery of the functional role of the chemistry [Dennett] |
| Full Idea: Neuro-science matters because - and only because - we have discovered that the many different neuromodulators and other chemical messengers that diffuse throughout the brain have functional roles that make important differences. | |
| From: Daniel C. Dennett (Sweet Dreams [2005], Ch.1) | |
| A reaction: I agree with Dennett that this is the true ground for pessimism about spectacular breakthroughs in artificial intelligence, rather than abstract concerns about irreducible features of the mind like 'qualia' and 'rationality'. |
| 19217 | I don't accept that if a proposition is directly about an entity, it has a relation to the entity [Merricks] |
| Full Idea: The Aboutness Assumption says that necessarily, if a proposition is directly about an entity, then that proposition stands in a relation to the entity. I shall argue that the Assumption is false. | |
| From: Trenton Merricks (Propositions [2015], 5.VII) | |
| A reaction: This feels sort of right, though the nature of aboutness remains elusive. He cites denials of existence. I take speech to be fairly internal, even though its main role is communication. Maybe its a Cambridge relation, as far as the entity is concerned. |
| 19203 | A sentence's truth conditions depend on context [Merricks] |
| Full Idea: A sentence has truth conditions only in a context of use. And the truth conditions of many sentences can differ from one context of use to another (as in 'I am a philosopher'). | |
| From: Trenton Merricks (Propositions [2015], 1.II) | |
| A reaction: He is building a defence of propositions, because they are eternal, and have their truth conditions essentially. I too am a fan of propositions. |
| 19200 | Propositions are standardly treated as possible worlds, or as structured [Merricks] |
| Full Idea: The thesis that propositions are sets of possible worlds is one of the two leading accounts of the nature of propositions. The other leading account endorses structured propositions. | |
| From: Trenton Merricks (Propositions [2015], Intro) | |
| A reaction: Merricks sets out to reject both main views. I take the idea that propositions actually are sets of possible worlds to be ridiculous (though they may offer a way of modelling them). The idea that they have no structure at all strikes me as odd. |
| 19206 | 'Cicero is an orator' represents the same situation as 'Tully is an orator', so they are one proposition [Merricks] |
| Full Idea: The proposition expressed by 'Cicero is an orator' represents things as being exactly the same way as does the proposition expressed by 'Tully is an orator'. Hence two sentences express the same proposition. Fregeans about names deny this. | |
| From: Trenton Merricks (Propositions [2015], 2.II) | |
| A reaction: Merricks makes the situation in the world fix the contents of the proposition. I don't agree. I would expand the first proposition as 'The person I know as 'Cicero' was an orator', but I might never have heard of 'Tully'. |
| 19202 | Propositions are necessary existents which essentially (but inexplicably) represent things [Merricks] |
| Full Idea: My account says that each proposition is a necessary existent that essentially represents things as being a certain way, ...and there is no explanation of how propositions do that. | |
| From: Trenton Merricks (Propositions [2015], Intro) | |
| A reaction: Since I take propositions to be brain events, I don't expect much of an explanation either. The idea that propositions necessarily exist strikes me as false. If there were no minds, there would have been no propositions. |
| 19204 | True propositions existed prior to their being thought, and might never be thought [Merricks] |
| Full Idea: 1,000 years ago, no sentence had ever expressed, and no one had believed, the true proposition 'a water molecule has two hydrogen and one oxygen atoms'. There are surely true propositions that have never been, and never will be, expressed or believed. | |
| From: Trenton Merricks (Propositions [2015], 1.V) | |
| A reaction: 'Surely'? Surely not! How many propositions exist? Where do they exist? What are they made of? If they already exist when we think them, how do we tune into them? When did his example come into existence? Before water did? No! No! |
| 19210 | The standard view of propositions says they never change their truth-value [Merricks] |
| Full Idea: The standard view among philosophers nowadays seems to be that propositions do not and even cannot change in truth-value. But my own view is that some propositions can, and do, change in truth value. | |
| From: Trenton Merricks (Propositions [2015], 3.VII) | |
| A reaction: He gives 'that A sits' as an example of one which can change, though 'that A sits at time t' cannot change. I take Merricks to be obviously right, and cannot get my head round the 'standard' view. What on earth do they think a proposition is? |
| 19201 | Propositions can be 'about' an entity, but that doesn't make the entity a constituent of it [Merricks] |
| Full Idea: If a singular proposition is 'directly about' an entity, I argue that a singular proposition does not have the entity that it is directly about as a constituent. | |
| From: Trenton Merricks (Propositions [2015], Intro) | |
| A reaction: This opposes the view of the early Russell, that propositions actually contain the entities they are about, thus making propositions real features of the external world. I take that view of Russell's to be absurd. |
| 19211 | Early Russell says a proposition is identical with its truthmaking state of affairs [Merricks] |
| Full Idea: I describe Russell's 1903 account of propositions as the view that each proposition is identical with the state of affairs that makes that proposition true. That is, a proposition is identical with its 'truthmaking' state of affairs. | |
| From: Trenton Merricks (Propositions [2015], 4.II) | |
| A reaction: Russell soon gave this view up (false propositions proving tricky), and I'm amazed anyone takes it seriously. I take it as axiomatic that if there were no minds there would be no propositions. Was the Big Bang a set of propositions? |
| 19212 | Unity of the proposition questions: what unites them? can the same constituents make different ones? [Merricks] |
| Full Idea: What binds the constituents of a structured proposition together into a single unity, a proposition? Can the very same constituents constitute two distinct propositions? These are questions about 'the unity of the proposition'. | |
| From: Trenton Merricks (Propositions [2015], 4.II) | |
| A reaction: Merricks solves it by saying propositions have no structure. The problem is connected to the nature of predication (instantiation, partaking). You can't just list objects and their properties. Objects are united, and thus propositions are too. |
| 19213 | We want to explain not just what unites the constituents, but what unites them into a proposition [Merricks] |
| Full Idea: A successful account of the unity of the proposition tells us what unites the relevant constituents not merely into some entity or other, but into a proposition. | |
| From: Trenton Merricks (Propositions [2015], 4.X) | |
| A reaction: Merrickes takes propositions to be unanalysable unities, but their central activity is representation, so if they needed uniting, that would be the place to look. Some people say that we unite our propositions. Others say the world does. I dunno. |