9 ideas
17751 | Gödel proved the completeness of first order predicate logic in 1930 [Gödel, by Walicki] |
Full Idea: Gödel proved the completeness of first order predicate logic in his doctoral dissertation of 1930. | |
From: report of Kurt Gödel (Completeness of Axioms of Logic [1930]) by Michal Walicki - Introduction to Mathematical Logic History E.2.2 |
11970 | Logicians like their entities to exhibit a maximum degree of purity [Kaplan] |
Full Idea: Logicians like their entities to exhibit a maximum degree of purity. | |
From: David Kaplan (Transworld Heir Lines [1967], p.97) | |
A reaction: An important observation, which explains why the modern obsession with logic has often led us down the metaphysical primrose path to ontological hell. |
11969 | Models nicely separate particulars from their clothing, and logicians often accept that metaphysically [Kaplan] |
Full Idea: The use of models is so natural to logicians ...that they sometimes take seriously what are only artefacts of the model, and adopt a bare particular metaphysics. Why? Because the model so nicely separates the bare particular from its clothing. | |
From: David Kaplan (Transworld Heir Lines [1967], p.97) | |
A reaction: See also Idea 11970. I think this observation is correct, and incredibly important. We need to keep quite separate the notion of identity in conceptual space from our notion of identity in the actual world. The first is bare, the second fat. |
11971 | The simplest solution to transworld identification is to adopt bare particulars [Kaplan] |
Full Idea: If we adopt the bare particular metaphysical view, we have a simple solution to the transworld identification problem: we identify by bare particulars. | |
From: David Kaplan (Transworld Heir Lines [1967], p.98) | |
A reaction: See Ideas 11969 and 11970 on this idea. The problem with bare particulars is that they can change their properties utterly, so that Aristotle in the actual world can be a poached egg in some possible world. We need essences. |
11973 | Unusual people may have no counterparts, or several [Kaplan] |
Full Idea: An extremely vivid person might have no counterparts, and Da Vinci seems to me to have more than one essence. Bertrand Russell is clearly the counterpart of at least three distinct persons in some more plausible world. | |
From: David Kaplan (Transworld Heir Lines [1967], p.100) | |
A reaction: Lewis prefers the notion that there is at most one counterpart, the 'closest' entity is some world. I think he also claims there is at least one counterpart. I like Kaplan's relaxed attitude to these things, which has more explanatory power. |
11972 | Essence is a transworld heir line, rather than a collection of properties [Kaplan] |
Full Idea: I prefer to think of essence as a transworld heir line, rather than as the more familiar collection of properties, because the latter too much suggests the idea of a fixed and final essential description. | |
From: David Kaplan (Transworld Heir Lines [1967], p.100) | |
A reaction: He is sympathetic to the counterpart idea, and close to Lewis's view of essences, as the intersection of counterparts. I like his rebellion against fixed and final descriptions, but am a bit doubtful about his basic idea. Causation should be involved. |
2614 | Modern phenomenalism holds that objects are logical constructions out of sense-data [Ayer] |
Full Idea: Nowadays phenomenalism is held to be a theory of perception which says that physical objects are logical constructions out of sense-data. | |
From: A.J. Ayer (Phenomenalism [1947], §1) |
2615 | The concept of sense-data allows us to discuss appearances without worrying about reality [Ayer] |
Full Idea: The introduction of the term 'sense-datum' is a means of referring to appearances without prejudging the question of what it is, if anything, that they are appearances of. | |
From: A.J. Ayer (Phenomenalism [1947], §1) |
11967 | Sentences might have the same sense when logically equivalent - or never have the same sense [Kaplan] |
Full Idea: Among the proposals for conditions under which two sentences have the same ordinary sense, the most liberal (Carnap and Church) is that they be logically equivalent, and the most restrictive (Benson Mates) is that they never have the same sense. | |
From: David Kaplan (Transworld Heir Lines [1967], p.89) | |
A reaction: Personally I would move the discussion to the level of the propositions being expressed before I attempted a solution. |