12 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) |
| 4692 | It is not true that killing and allowing to die (or acts and omissions) are morally indistinguishable [Foot] |
| Full Idea: Many philosophers (e.g. Rachels) have argued that there is no morally relevant distinction between killing and allowing to die (or the related 'acts and omissions'),..as in not sending food, or sending poisoned food. I disagree. | |
| From: Philippa Foot (Killing and Letting Die [1985], p.78) | |
| A reaction: It appears that some omissions are worse than acts. It is more honest to just shoot an injured person, than to walk away and leave them to die. A range of cases. |
| 4694 | Making a runaway tram kill one person instead of five is diverting a fatal sequence, not initiating one [Foot] |
| Full Idea: If a runaway tram is heading towards a track on which five people are standing, and there is someone who can switch the points, diverting it onto a track where there is one person,...this is diverting a fatal sequence, not starting a new one. | |
| From: Philippa Foot (Killing and Letting Die [1985], p.85) | |
| A reaction: Suppose the one person was of immense community value, or someone you personally hated? Clearly she is interested in the agent's virtue, rather than the actual consequences. |
| 4693 | The right of non-interference (with a 'negative duty'), and the right to goods/services ('positive') [Foot] |
| Full Idea: There are rights to non-interference (and their corresponding "negative duties"), and the rights to goods and services (with corresponding "positive duties"). Interference usually needs more justification than withholding goods. | |
| From: Philippa Foot (Killing and Letting Die [1985], p.82) | |
| A reaction: This invites the question of which is the stronger, and whether paternalism can overrule non-interference, or an expectation of self-sufficiency overrule the positive rights. |
| 4054 | I may exist before I become a person, just as I exist before I become an adult [Lockwood] |
| Full Idea: It makes perfectly good sense to say that I existed before I became a person, just as I existed before I became an adult, or a philosopher. | |
| From: Michael Lockwood (When Does a Life Begin? [1985], p.13) | |
| A reaction: The word 'I' needs thought here. I was once a non-adult, but was I ever a non-person? 'Person' is not a clear concept, despite what many philosophers since Locke may think. |
| 4056 | If the soul is held to leave the body at brain-death, it should arrive at the time of brain-creation [Lockwood] |
| Full Idea: Any Christian who feels that body and soul go their separate ways at brain death ought in consistency to hold that they come together only at the point when whatever is destroyed at brain death first came into being. | |
| From: Michael Lockwood (When Does a Life Begin? [1985], p.24) | |
| A reaction: Hence Christians probably focus less on brain-death than do doctors and the rest of us. |
| 4055 | It isn't obviously wicked to destroy a potential human being (e.g. an ununited egg and sperm) [Lockwood] |
| Full Idea: A week-old embryo without a brain may be a potential human being, but so are a sperm and an ovum that are about to meet in a dish, and it wouldn't be wicked to keep those apart. | |
| From: Michael Lockwood (When Does a Life Begin? [1985], p.19) | |
| A reaction: Sounds fine, but it may be a slippery slope. Is it acceptable to deny a place at music school to a potentially great musician? |