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) |
| 6900 | A prior understanding of beauty is needed to assert that the Form of the Beautiful is beautiful [Westaway] |
| Full Idea: If it were asserted that the Form of the Beautiful was itself beautiful, such a statement would require a prior understanding of the concept of beauty, so would immediately lead to an infinite regress, so the Forms can't be self-predicating. | |
| From: Luke Westaway (talk [2005]), quoted by PG - Db (ideas) | |
| A reaction: This is a nice clear statement of the mess that Plato gets himself into if he wants the Forms to be self-predicating. Clearly the Form of the Beautiful can't be beautiful, but must be that which gives other things their beauty. |
| 6956 | At what point does an object become 'whole'? [Westaway] |
| Full Idea: At what point does an object become 'whole'? | |
| From: Luke Westaway (talk [2005]), quoted by PG - Db (ideas) | |
| A reaction: This nice question strikes me as the central one in mereology. It is tempting to reply that the matter is entirely conventional, but there seems an obvious fact about something missing if one piece is absent from a jigsaw, or a cube is chipped. |
| 7335 | The Chinese Room should be able to ask itself questions in Mandarin [Westaway] |
| Full Idea: If the Chinese Room is functionally equivalent to a Mandarin speaker, it ought to be able to ask itself questions in Mandarin (and it can't). | |
| From: Luke Westaway (talk [2005]), quoted by PG - Db (ideas) | |
| A reaction: Searle might triumphantly say that this proves there is no understanding in the room, but the objection won't go away, because the room is presumably functionally equivalent to a speaker, and not just a mere translator (who might use mechanical tricks). |
| 16764 | The soul conserves the body, as we see by its dissolution when the soul leaves [Toletus] |
| Full Idea: Every accident of a living thing, as well as all its organs and temperaments and its dispositions are conserved by the soul. We see this from experience, since when that soul recedes, all these dissolve and become corrupted. | |
| From: Franciscus Toletus (Commentary on 'De Anima' [1572], II.1.1), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 24.5 | |
| A reaction: A nice example of observing a phenemonon, but not being able to observe the dependence relation the right way round. Compare Descartes in Idea 16763. |