8 ideas
| 18085 | Values that approach zero, becoming less than any quantity, are 'infinitesimals' [Cauchy] |
| Full Idea: When the successive absolute values of a variable decrease indefinitely in such a way as to become less than any given quantity, that variable becomes what is called an 'infinitesimal'. Such a variable has zero as its limit. | |
| From: Augustin-Louis Cauchy (Cours d'Analyse [1821], p.19), quoted by Philip Kitcher - The Nature of Mathematical Knowledge 10.4 | |
| A reaction: The creator of the important idea of the limit still talked in terms of infinitesimals. In the next generation the limit took over completely. |
| 18084 | When successive variable values approach a fixed value, that is its 'limit' [Cauchy] |
| Full Idea: When the values successively attributed to the same variable approach indefinitely a fixed value, eventually differing from it by as little as one could wish, that fixed value is called the 'limit' of all the others. | |
| From: Augustin-Louis Cauchy (Cours d'Analyse [1821], p.19), quoted by Philip Kitcher - The Nature of Mathematical Knowledge 10.4 | |
| A reaction: This seems to be a highly significan proposal, because you can now treat that limit as a number, and adds things to it. It opens the door to Cantor's infinities. Is the 'limit' just a fiction? |
| 22593 | Our sensation of light may not be the same as what produces the sensation [Descartes] |
| Full Idea: There can be a difference between our sensation of light and what is in the objects that produce that sensation in us. | |
| From: René Descartes (The World [1631]), quoted by Ian Dunt - How to be a Liberal 1 | |
| A reaction: Note only that they 'may' differ, and that he does not assert that they are entirely different. Secondary qualities give information, and are not just mental events. |
| 21004 | Hart (against Bentham) says human rights are what motivate legal rights [Hart,HLA, by Sen] |
| Full Idea: Whereas Bentham saw rights as a 'child of law', Herbert Hart's view takes the form of seeing human rights as, in effect, 'parents of law'; they motivate specific legislations. | |
| From: report of H.L.A. Hart (The Concept of Law [1961]) by Amartya Sen - The Idea of Justice 17 'Ethics' | |
| A reaction: [He cites Hart 1955 'Are there any natural rights?'] I agree with Hart. It is clearer if the parents of law are not referred to as 'rights'. You can demand a right, but it is only a right when it is awarded to you. |
| 20932 | Positive law needs secondary 'rules of recognition' for their correct application [Hart,HLA, by Zimmermann,J] |
| Full Idea: Hart says we have secondary legal 'rules of recognition', by which primary positive law is recognised and applied in a regulated manner. | |
| From: report of H.L.A. Hart (The Concept of Law [1961]) by Jens Zimmermann - Hermeneutics: a very short introduction 6 'Rules' | |
| A reaction: The example of the authority of a particular court is given. |
| 20931 | Hart replaced positivism with the democratic requirement of the people's acceptance [Hart,HLA, by Zimmermann,J] |
| Full Idea: Hart replaced Austin's concept of positive law as sovereign command with a more democratic ideal. In modern law-based societies the authority of law depends on the people's acceptance of a law's enduring validity. | |
| From: report of H.L.A. Hart (The Concept of Law [1961]) by Jens Zimmermann - Hermeneutics: a very short introduction 6 'Hart' | |
| A reaction: Presumably the ancestor of this view is the social contract of Hobbes and Locke. |
| 16569 | The Hot, Cold, Wet and Dry of the philosophers need themselves to be explained [Descartes] |
| Full Idea: If you find it strange that in explaining these elements I do not use the qualities called Hot, Cold, Wet and Dry - as the philosophers do - I shall say to you that these qualities themselves seem to me to need explanation. | |
| From: René Descartes (The World [1631], 9:25-6), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 1.3 | |
| A reaction: Nice. I take pushing the boundaries of explanation back (or down) to be the basic driving force of all human thought, in metaphysics as well as in physics. |
| 20964 | Descartes said there was conservation of 'quantity of motion' [Descartes, by Papineau] |
| Full Idea: Descartes incorporated the conservation of what he called 'quantity of motion', by which he meant mass times speed. | |
| From: report of René Descartes (The World [1631]) by David Papineau - Thinking about Consciousness App 2 | |
| A reaction: Mass times velocity is now called 'momentum'. Is this the first ever conservation law? There are now lots of them. |