10 ideas
| 17884 | Mathematical set theory has many plausible stopping points, such as finitism, and predicativism [Koellner] |
| Full Idea: There are many coherent stopping points in the hierarchy of increasingly strong mathematical systems, starting with strict finitism, and moving up through predicativism to the higher reaches of set theory. | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], Intro) |
| 17893 | 'Reflection principles' say the whole truth about sets can't be captured [Koellner] |
| Full Idea: Roughly speaking, 'reflection principles' assert that anything true in V [the set hierarchy] falls short of characterising V in that it is true within some earlier level. | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], 2.1) |
| 17894 | We have no argument to show a statement is absolutely undecidable [Koellner] |
| Full Idea: There is at present no solid argument to the effect that a given statement is absolutely undecidable. | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], 5.3) |
| 17890 | There are at least eleven types of large cardinal, of increasing logical strength [Koellner] |
| Full Idea: Some of the standard large cardinals (in order of increasing (logical) strength) are: inaccessible, Mahlo, weakly compact, indescribable, Erdös, measurable, strong, Wodin, supercompact, huge etc. (...and ineffable). | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], 1.4) | |
| A reaction: [I don't understand how cardinals can have 'logical strength', but I pass it on anyway] |
| 17887 | PA is consistent as far as we can accept, and we expand axioms to overcome limitations [Koellner] |
| Full Idea: To the extent that we are justified in accepting Peano Arithmetic we are justified in accepting its consistency, and so we know how to expand the axiom system so as to overcome the limitation [of Gödel's Second Theorem]. | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], 1.1) | |
| A reaction: Each expansion brings a limitation, but then you can expand again. |
| 17891 | Arithmetical undecidability is always settled at the next stage up [Koellner] |
| Full Idea: The arithmetical instances of undecidability that arise at one stage of the hierarchy are settled at the next. | |
| From: Peter Koellner (On the Question of Absolute Undecidability [2006], 1.4) |
| 18948 | There is an object for every set of properties (some of which exist, and others don't) [Parsons,T, by Sawyer] |
| Full Idea: According to Terence Parsons, there is an object corresponding to every set of properties. To some of those sets of properties there corresponds an object that exists, and to others there corresponds an object that does not exist (a nonexistent object). | |
| From: report of Terence Parsons (Nonexistent Objects [1980]) by Sarah Sawyer - Empty Names 5 | |
| A reaction: This I take to be the main source of the modern revival of Meinong's notorious view of objects (attacked by Russell). I always find the thought 'a round square is square' to be true, and in need of a truthmaker. But must a round square be non-triangular? |
| 7522 | A full neural account of qualia will give new epistemic access to them, beyond private experience [Churchlands] |
| Full Idea: When the hidden neurophysiological structure of qualia (if there is any) gets revealed by unfolding research, then we will automatically gain a new epistemic access to qualia, beyond each person's native and exclusive capacity for internal discrimination. | |
| From: Churchland / Churchland (Recent Work on Consciousness [1997]) | |
| A reaction: Carefully phrased and hard to deny, but something is impenetrable. What experience does an insect have when it encounters ultra-violet light? Nothing remotely interesting about their qualia is likely to emerge from the study of insect brains. |
| 7521 | It is question-begging to assume that qualia are totally simple, hence irreducible [Churchlands] |
| Full Idea: One of the crucial premises of the antireductionists - concerning the intrinsic, nonrelational, metaphysical simplicity of our sensory qualia - is a question-begging and unsupported assumption. | |
| From: Churchland / Churchland (Recent Work on Consciousness [1997]) | |
| A reaction: This is a key point for reductionists, with emphasis on the sheer numbers of connections involved in a simple quale (I estimate a billion involved in one small patch of red). |
| 7523 | The qualia Hard Problem is easy, in comparison with the co-ordination of mental states [Churchlands] |
| Full Idea: The so-called Hard Problem (of qualia) appears to be one of the easiest, in comparison with the problems of short-term memory, fluid and directable attention, the awake state vs sleep, and the unity of consciousness. | |
| From: Churchland / Churchland (Recent Work on Consciousness [1997]) | |
| A reaction: Most of their version of the Hard Problems centre on personal identity, and the centralised co-ordination of mental events. I am inclined to agree with them. Worriers about qualia should think more about the complexity of systems of neurons. |