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2 ideas
| 9667 | Mereological composition is unrestricted: any class of things has a mereological sum [Lewis] |
| Full Idea: I claim that mereological composition is unrestricted: any old class of things has a mereological sum. Whenever there are some things, even out of different possible worlds, there is something composed of just those things. | |
| From: David Lewis (On the Plurality of Worlds [1986], 4.3) | |
| A reaction: To say the least, a rather unusual usage for the English word 'thing'. I presume that Lewis is in the grip of a slippery slope problem - that there is no way to define the borderline between things and non-things. Presumably 'class' is unrestricted too. |
| 13268 | There are no restrictions on composition, because they would be vague, and composition can't be vague [Lewis, by Sider] |
| Full Idea: Lewis says that if not every class has a fusion then there must be a restriction on composition. The only plausible restrictions would be vague ones, which is impossible, because then whether composition occurs would be vague. So every class has a fusion. | |
| From: report of David Lewis (On the Plurality of Worlds [1986], p.212-3) by Theodore Sider - Four Dimensionalism 9.1 | |
| A reaction: This is Lewis's key argument in favour of unrestricted composition, his Vagueness Argument. Why can't composition be vague? If you gradually reassemble a broken mirror, at what point does the mirror acquire its unity? |