7 ideas
| 14361 | Lewis says indicative conditionals are truth-functional [Lewis, by Jackson] |
| Full Idea: Unlike Stalnaker, Lewis holds that indicative conditionals have the truth conditions of material conditionals. | |
| From: report of David Lewis (Counterfactuals [1973]) by Frank Jackson - Conditionals 'Further' | |
| A reaction: Thus Lewis only uses the possible worlds account for subjunctive conditionals, where Stalnaker uses it for both. Lewis is defending the truth-functional account for the indicative conditionals. |
| 8434 | In good counterfactuals the consequent holds in world like ours except that the antecedent is true [Lewis, by Horwich] |
| Full Idea: According to Lewis, a counterfactual holds when the consequent is true in possible worlds very like our own except for the fact that the antecedent is true. | |
| From: report of David Lewis (Counterfactuals [1973]) by Paul Horwich - Lewis's Programme p.213 | |
| A reaction: Presumably the world being very like our own would make it unlikely that there would be anything else to cause the consequent, apart from the counterfactual antecedent. |
| 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. |
| 9419 | A law of nature is a general axiom of the deductive system that is best for simplicity and strength [Lewis] |
| Full Idea: A contingent generalization is a law of nature if and only if it appears as a theorem (or axiom) in each of the true deductive systems that achieves a best combination of simplicity and strength. | |
| From: David Lewis (Counterfactuals [1973], 3.3) |
| 11945 | In addition to laws, God must also create appropriate natures for things [Leibniz] |
| Full Idea: It isn't sufficient to say that God has made a general law, for in addition to the decree there has also to be a natural way of carrying it out. It is necessary, that is, that what happens should be explicable in terms of the God-given nature of things. | |
| From: Gottfried Leibniz (Letter to the Editor about Bayle [1698], p.205) | |
| A reaction: Thus Leibniz is an ancestor of scientific essentialism, but he was too frightened to take the next step, which is to see that once God has endowed the natures, he doesn't need to wield his laws as well. The natures will do the whole job. |
| 19348 | All that is real in motion is the force or power which produces change [Leibniz] |
| Full Idea: As for motion, what is real in it is force or power; that is to say, what there is in the present state which carries with it a change in the future. The rest is only phenomena and relations. | |
| From: Gottfried Leibniz (Letter to the Editor about Bayle [1698], §13) | |
| A reaction: This presumably contradicts Newton's concept of inertia, which allows constant motion without force. I always like a reference to powers. What is 'kinetic energy' in this context? |
| 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. |