3 ideas
| 18189 | ZFC could contain a contradiction, and it can never prove its own consistency [MacLane] |
| Full Idea: We have at hand no proof that the axioms of ZFC for set theory will never yield a contradiction, while Gödel's second theorem tells us that such a consistency proof cannot be conducted within ZFC. | |
| From: Saunders MacLane (Mathematics: Form and Function [1986], p.406), quoted by Penelope Maddy - Naturalism in Mathematics | |
| A reaction: Maddy quotes this, while defending set theory as the foundation of mathematics, but it clearly isn't the most secure foundation that could be devised. She says the benefits of set theory do not need guaranteed consistency (p.30). |
| 15456 | Extrinsic properties, unlike intrinsics, imply the existence of a separate object [Kim, by Lewis] |
| Full Idea: Kim suggest that 'extrinsic' properties are those that imply 'accompaniment' (coexisting with some wholly distinct contingent object), whereas 'intrinsic' properties are compatible with 'loneliness' (being un-accompanied). | |
| From: report of Jaegwon Kim (Psychophysical supervenience [1982], 9th pg) by David Lewis - Extrinsic Properties II | |
| A reaction: The aim of Kim and Lewis is to get the ontological commitment down to a minimum - in this case just to objects (and mysterious 'implications'!). I like nominalism, but you can't just deny properties. 'Loneliness' is extrinsic! |
| 490 | Everything happens by reason and necessity [Leucippus] |
| Full Idea: Nothing happens at random; everything happens out of reason and by necessity. | |
| From: Leucippus (fragments/reports [c.435 BCE], B002), quoted by (who?) - where? |