display all the ideas for this combination of texts
2 ideas
| 5401 | The mortality of Socrates is more certain from induction than it is from deduction [Russell] |
| Full Idea: We would do better to go straight from the evidence that some men have died to the mortality of Socrates, than to go via 'all men are mortal', for the probability that Socrates is mortal is greater than the probability that all men are mortal. | |
| From: Bertrand Russell (Problems of Philosophy [1912], Ch. 7) | |
| A reaction: Russell claims that deduction should stick to a priori truth, and induction is best for the real world. Interesting. To show that something is a member of a set (e.g. planets) you need an awful lot of knowledge of the set. |
| 9456 | Modal logic is multiple systems, shown in the variety of accessibility relations between worlds [Jacquette] |
| Full Idea: Modal logic by its very nature is not monolithic, but fragmented into multiple systems of modal qualifications, reflected in the plurality of accessibility relations on modal model structures or logically possible worlds. | |
| From: Dale Jacquette (Intro to 'Philosophy of Logic' [2002], §3) | |
| A reaction: He implies the multiplicity is basic, and is only 'reflected' in the relations, but maybe the multiplicity is caused by incompetent logicians who can't decide whether possible worlds really are reflexive or symmetrical or transitive in their relations. |