18 ideas
9193 | ZF set theory has variables which range over sets, 'equals' and 'member', and extensionality [Dummett] |
9194 | The main alternative to ZF is one which includes looser classes as well as sets [Dummett] |
9195 | Intuitionists reject excluded middle, not for a third value, but for possibility of proof [Dummett] |
9186 | First-order logic concerns objects; second-order adds properties, kinds, relations and functions [Dummett] |
9187 | Logical truths and inference are characterized either syntactically or semantically [Dummett] |
9191 | Ordinals seem more basic than cardinals, since we count objects in sequence [Dummett] |
9192 | The number 4 has different positions in the naturals and the wholes, with the same structure [Dummett] |
21110 | An understanding of the most basic physics should explain all of the subject's mysteries [Krauss] |
21105 | In 1676 it was discovered that water is teeming with life [Krauss] |
13304 | Learned men gain more in one day than others do in a lifetime [Posidonius] |
21109 | Space itself can expand (and separate its contents) at faster than light speeds [Krauss] |
21104 | General Relativity: the density of energy and matter determines curvature and gravity [Krauss] |
21107 | Uncertainty says that energy can be very high over very short time periods [Krauss] |
21106 | Most of the mass of a proton is the energy in virtual particles (rather than the quarks) [Krauss] |
21112 | Empty space contains a continual flux of brief virtual particles [Krauss] |
20820 | Time is an interval of motion, or the measure of speed [Posidonius, by Stobaeus] |
21108 | The universe is precisely 13.72 billion years old [Krauss] |
21111 | It seems likely that cosmic inflation is eternal, and this would make a multiverse inevitable [Krauss] |