19 ideas
| 19740 | A very hungry man cannot choose between equidistant piles of food [Aristotle] |
| Full Idea: The man who, though exceedingly hungry and thirsty, and both equally, yet being equidistant from food and drink, is therefore bound to stay where he is. | |
| From: Aristotle (On the Heavens [c.336 BCE], 296b33) | |
| A reaction: This is, of course, Buridan's famous Ass, but this quotation has the advantage of precedence, and also of being expressed in an original quotation (which does not exist for Buridan). |
| 16489 | Is it possible to state every possible truth about the whole course of nature without using 'not'? [Russell] |
| Full Idea: Imagine a person who knew everything that can be stated without using the word 'not' or some equivalent; would such a person know the whole course of nature, or would he not? | |
| From: Bertrand Russell (Human Knowledge: its scope and limits [1948], 9) | |
| A reaction: Nowadays we might express Russell's thought as 'Does God need the word 'not'?'. Russell's thesis is that such words concern psychology, and not physics. God would need 'not' to describe how human minds work. |
| 16490 | Some facts about experience feel like logical necessities [Russell] |
| Full Idea: The impossibility of seeing two colours simultaneously in a given direction feels like a logical impossibility. | |
| From: Bertrand Russell (Human Knowledge: its scope and limits [1948], 9) | |
| A reaction: I presume all necessities feel equally necessary. If we distinguish necessities by what gives rise to them (a view I favour) then how strong they 'feel' will be irrelevant. We can see why Russell is puzzled by the phenomenon, though. |
| 16488 | It is hard to explain how a sentence like 'it is not raining' can be found true by observation [Russell] |
| Full Idea: If 'it is not raining' means 'the sentence "it is raining" is false', that makes it almost impossible to understand how a sentence containing the word 'not' can be found true by observation. | |
| From: Bertrand Russell (Human Knowledge: its scope and limits [1948], 9) | |
| A reaction: Russell goes on to explore the general difficulty of deciding negative truths by observation. The same problem arises for truthmaker theory. Obviously I can observe that it isn't raining, but it seems parasitic on observing when it is raining. |
| 16491 | If we define 'this is not blue' as disbelief in 'this is blue', we eliminate 'not' as an ingredient of facts [Russell] |
| Full Idea: We can reintroduce 'not' by a definition: the words 'this is not blue' are defined as expressing disbelief in what is expressed by the words 'this is blue'. In this way the need of 'not' as an indefinable constituent of facts is avoided. | |
| From: Bertrand Russell (Human Knowledge: its scope and limits [1948], 9) | |
| A reaction: This is part of Russell's programme of giving a psychological account of logical connectives. See other ideas from his 1940 and 1948 works. He observes that disbelief is a state just as positive as belief. I love it. |
| 398 | Each thing that has a function is for the sake of that function [Aristotle] |
| Full Idea: Each thing that has a function is for the sake of that function. | |
| From: Aristotle (On the Heavens [c.336 BCE], 286a08) | |
| A reaction: This is the central idea of Aristotle's Ethics. Did it originate with Plato, or Socrates, the young pupil Aristotle? I suspect the strong influence of Aristotle on later Plato. A major idea. Functions link the facts to life. |
| 13304 | Learned men gain more in one day than others do in a lifetime [Posidonius] |
| Full Idea: In a single day there lies open to men of learning more than there ever does to the unenlightened in the longest of lifetimes. | |
| From: Posidonius (fragments/reports [c.95 BCE]), quoted by Seneca the Younger - Letters from a Stoic 078 | |
| A reaction: These remarks endorsing the infinite superiority of the educated to the uneducated seem to have been popular in late antiquity. It tends to be the religions which discourage great learning, especially in their emphasis on a single book. |
| 394 | An unworn sandal is in vain, but nothing in nature is in vain [Aristotle] |
| Full Idea: We say of a sandal which is not worn that it is in vain; God and nature, however, do nothing in vain. | |
| From: Aristotle (On the Heavens [c.336 BCE], 271a33) |
| 396 | There has to be some goal, and not just movement to infinity [Aristotle] |
| Full Idea: There has to be some goal, and not just movement to infinity. | |
| From: Aristotle (On the Heavens [c.336 BCE], 277a26) |
| 16102 | Aether moves in circles and is imperishable; the four elements perish, and move in straight lines [Aristotle, by Gill,ML] |
| Full Idea: For Aristotle, aether and the four sublunary elements obey different physical laws. Aether moves naturally in a circle and, unlike its lower counterparts, is not a source of perishability. The four sublunary elements move naturally in straight lines. | |
| From: report of Aristotle (On the Heavens [c.336 BCE]) by Mary Louise Gill - Aristotle on Substance Ch.2 | |
| A reaction: I think it is anachronistic for Gill to talk of 'obeying' and 'laws'. She should have said that they have different 'natures'. We can be amused by Greek errors, until we stare hard at the problems they were trying to solve. |
| 17463 | An element is what bodies are analysed into, and won't itself divide into something else [Aristotle] |
| Full Idea: An element is a body into which other bodies may be analyzed, present in them potentially or in actuality (which of these is still disputable), and not itself divisible into bodies different in form. That is what all men mean by element. | |
| From: Aristotle (On the Heavens [c.336 BCE], 302a05), quoted by Weisberg/Needham/Hendry - Philosophy of Chemistry 1.1 | |
| A reaction: This is the classic definition of an element, which endured for a long time, and has been replaced by an 'actual components' view. Obviously analysis nowadays goes well beyond the atoms. |
| 399 | If the more you raise some earth the faster it moves, why does the whole earth not move? [Aristotle] |
| Full Idea: If you raise some earth and release it, it moves and won't stay put, and the more you raise it the faster it moves, so why does the whole earth not move? | |
| From: Aristotle (On the Heavens [c.336 BCE], 294a12) |
| 4786 | Russell's 'at-at' theory says motion is to be at the intervening points at the intervening instants [Russell, by Psillos] |
| Full Idea: To reply to Zeno's Arrow Paradox, Russell developed his 'at-at' theory of motion, which says that to move from A to B is to be at the intervening points at the intervening instants. | |
| From: report of Bertrand Russell (Human Knowledge: its scope and limits [1948]) by Stathis Psillos - Causation and Explanation §4.2 | |
| A reaction: I wonder whether Russell's target was actually Zeno, or was it a simplified ontology of points and instants? The ontology will also need identity, to ensure it is the same thing which arrives at each point. |
| 20918 | Void is a kind of place, so it can't explain place [Aristotle] |
| Full Idea: It is absurd to explain place by the void, as though this latter were not itself some kind of place. | |
| From: Aristotle (On the Heavens [c.336 BCE], 309b24) | |
| A reaction: Presumably this is aimed at Democritus. |
| 20820 | Time is an interval of motion, or the measure of speed [Posidonius, by Stobaeus] |
| Full Idea: Posidonius defined time thus: it is an interval of motion, or the measure of speed and slowness. | |
| From: report of Posidonius (fragments/reports [c.95 BCE]) by John Stobaeus - Anthology 1.08.42 | |
| A reaction: Hm. Can we define motion or speed without alluding to time? Looks like we have to define them as a conjoined pair, which means we cannot fully understand either of them. |
| 402 | The Earth must be spherical, because it casts a convex shadow on the moon [Aristotle] |
| Full Idea: A lunar eclipse always has a convex dividing line, so, if it is eclipsed by the interposition of the earth, the circumference of the earth, being spherical, is responsible for the shape. | |
| From: Aristotle (On the Heavens [c.336 BCE], 297b29) |
| 403 | The earth must be round and of limited size, because moving north or south makes different stars visible [Aristotle] |
| Full Idea: Clearly the earth is round and not of great size, because when we move north or south we find that very different stars are visible. | |
| From: Aristotle (On the Heavens [c.336 BCE], 297b30) |
| 1498 | Everyone agrees that the world had a beginning, but thinkers disagree over whether it will end [Aristotle] |
| Full Idea: All thinkers agree that the world had a beginning, but some claim that, having come into existence, it is everlasting. | |
| From: Aristotle (On the Heavens [c.336 BCE], 279b12) |
| 395 | It seems possible that there exists a limited number of other worlds apart from this one [Aristotle] |
| Full Idea: One might indeed be puzzled whether, just as the world about us exists, nothing prevents there being others as well, certainly more than one, though not an unlimited number | |
| From: Aristotle (On the Heavens [c.336 BCE], 274a26) |