22 ideas
5515 | Imaginary cases are good for revealing our beliefs, rather than the truth [Parfit] |
10301 | The axiom of choice is controversial, but it could be replaced [Shapiro] |
10588 | First-order logic is Complete, and Compact, with the Löwenheim-Skolem Theorems [Shapiro] |
10298 | Some say that second-order logic is mathematics, not logic [Shapiro] |
10299 | If the aim of logic is to codify inferences, second-order logic is useless [Shapiro] |
10300 | Logical consequence can be defined in terms of the logical terminology [Shapiro] |
10290 | Second-order variables also range over properties, sets, relations or functions [Shapiro] |
10590 | Up Löwenheim-Skolem: if natural numbers satisfy wffs, then an infinite domain satisfies them [Shapiro] |
10296 | The Löwenheim-Skolem Theorems fail for second-order languages with standard semantics [Shapiro] |
10297 | The Löwenheim-Skolem theorem seems to be a defect of first-order logic [Shapiro] |
10292 | Downward Löwenheim-Skolem: if there's an infinite model, there is a countable model [Shapiro] |
10294 | Second-order logic has the expressive power for mathematics, but an unworkable model theory [Shapiro] |
5516 | Reduction can be by identity, or constitution, or elimination [Parfit, by PG] |
10591 | Logicians use 'property' and 'set' interchangeably, with little hanging on it [Shapiro] |
579 | Cratylus said you couldn't even step into the same river once [Cratylus, by Aristotle] |
578 | Cratylus decided speech was hopeless, and his only expression was the movement of a finger [Cratylus, by Aristotle] |
5514 | Psychologists are interested in identity as a type of person, but philosophers study numerical identity [Parfit] |
5521 | If my brain-halves are transplanted into two bodies, I have continuity, and don't need identity [Parfit] |
5522 | Over a period of time what matters is not that 'I' persist, but that I have psychological continuity [Parfit] |
5519 | It is fine to save two dying twins by merging parts of their bodies into one, and identity is irrelevant [Parfit] |
5520 | If two humans are merged surgically, the new identity is a purely verbal problem [Parfit] |
5518 | It doesn't matter whether I exist with half my components replaced (any more than an audio system) [Parfit] |