display all the ideas for this combination of texts
8 ideas
| 20819 | The past and the future subsist, but only the present exists [Chrysippus, by Plutarch] |
| Full Idea: When he wished to be subtle, Chrysippus wrote that the past part of time and the future part do not exist but subsist, and only the present exists. | |
| From: report of Chrysippus (fragments/reports [c.240 BCE]) by Plutarch - On Common Conceptions 1081f | |
| A reaction: [from lost On Void] I think I prefer the ontology of Idea 20818. Idea 20819 does not offer an epistemology. Is the present substantial enough to be known? The word 'subsist' is an ontological evasion (even though Russell briefly relied on it). |
| 20818 | The present does not exist, so our immediate experience is actually part past and part future [Chrysippus, by Plutarch] |
| Full Idea: Stoics do not allow a minimal time to exist, and do not want to have a partless 'now'; so what one thinks one has grasped as present is in part future and in part past. | |
| From: report of Chrysippus (fragments/reports [c.240 BCE]) by Plutarch - On Common Conceptions 1081c | |
| A reaction: [from lost On Parts Bk3-5] I agree with the ontology here, but I take our grasp of the present to be very short-term memory of the past. I ignore special relativity. Chrysippus expressed two views about this; in the other one he was a Presentist. |
| 20821 | Time is continous and infinitely divisible, so there cannot be a wholly present time [Chrysippus, by Stobaeus] |
| Full Idea: Chrysippus says most clearly that no time is wholly present; for since the divisibility of continuous things is infinite, time as a whole is also subject to infinite divisibility by this method of division. | |
| From: report of Chrysippus (fragments/reports [c.240 BCE]) by John Stobaeus - Anthology 1.08.42 | |
| A reaction: But what is his reason for thinking that time is a continuous thing? There is a minimum time in quantum mechanics (the Planck Time), but do these quantum intervals overlap? Compare Idea 20819. |
| 17482 | Compounds can differ with the same collection of atoms, so structure matters too [Hendry] |
| Full Idea: The distinctness of the isomers ethanol (CH3CH2OH, boiling at 78.4°) and dimethyl ether (CH3OCH3, boiling at -24.9°) must lie in their different molecular structures. ...But structure has continuously varying quantities, like bond length and angle. | |
| From: Robin F. Hendry (Chemistry [2008], 'Micro') | |
| A reaction: [compressed] This seems to imply that what matters is an idealised abstraction of the structure (i.e. its topology), which is a reason for denying that chemistry is reducible to mere physics. |
| 17483 | Water continuously changes, with new groupings of molecules [Hendry] |
| Full Idea: Macroscopic bodies of water are complex and dynamic congeries of different molecular species, in which there is a constant dissociation of individual molecules, re-association of ions, and formation, growth and disassociation of oligomers. | |
| From: Robin F. Hendry (Chemistry [2008], 'Micro') | |
| A reaction: The point is that these activities are needed to explain the behaviour of water (such as its conductivity). |
| 17476 | Elements survive chemical change, and are tracked to explain direction and properties [Hendry] |
| Full Idea: Elements survive chemical change, and chemical explanations track them from one composite substance to another, thereby explaining both the direction of the chemical change, and the properties of the substances they compose. | |
| From: Robin F. Hendry (Chemistry [2008], Intro) | |
| A reaction: [The 16,000th idea of this database, entered on Guy Fawkes' Day 2013] |
| 17477 | Defining elements by atomic number allowed atoms of an element to have different masses [Hendry] |
| Full Idea: In 1923 elements were defined as populations of atoms with the same nuclear charge (i.e. atomic number), allowing that atoms of the same element may have different masses. | |
| From: Robin F. Hendry (Chemistry [2008], 'Chem') | |
| A reaction: The point is that it allowed isotopes of the same element to come under one heading. This is fine for the heavier elements, but a bit dubious for the very light ones (where an isotope makes a bigger difference). |
| 17480 | Generally it is nuclear charge (not nuclear mass) which determines behaviour [Hendry] |
| Full Idea: In general, nuclear charge is the overwhelming determinant of an element's chemical behaviour, while nuclear mass is a negligible factor. | |
| From: Robin F. Hendry (Chemistry [2008], 'Micro') | |
| A reaction: The exception is the isotopes of very light elements light hydrogen. |