9 ideas
| 9540 | A 'value-assignment' (V) is when to each variable in the set V assigns either the value 1 or the value 0 [Hughes/Cresswell] |
| Full Idea: A 'value-assignment' (V) is when to each variable in the set V assigns either the value 1 or the value 0. | |
| From: GE Hughes/M Cresswell (An Introduction to Modal Logic [1968], Ch.1) | |
| A reaction: In the interpreted version of the logic, 1 and 0 would become T (true) and F (false). The procedure seems to be called nowadays a 'valuation'. |
| 9541 | The Law of Transposition says (P→Q) → (¬Q→¬P) [Hughes/Cresswell] |
| Full Idea: The Law of Transposition says that (P→Q) → (¬Q→¬P). | |
| From: GE Hughes/M Cresswell (An Introduction to Modal Logic [1968], Ch.1) | |
| A reaction: That is, if the consequent (Q) of a conditional is false, then the antecedent (P) must have been false. |
| 9543 | The rules preserve validity from the axioms, so no thesis negates any other thesis [Hughes/Cresswell] |
| Full Idea: An axiomatic system is most naturally consistent iff no thesis is the negation of another thesis. It can be shown that every axiom is valid, that the transformation rules are validity-preserving, and if a wff α is valid, then ¬α is not valid. | |
| From: GE Hughes/M Cresswell (An Introduction to Modal Logic [1968], Ch.1) | |
| A reaction: [The labels 'soundness' and 'consistency' seem interchangeable here, with the former nowadays preferred] |
| 9544 | A system is 'weakly' complete if all wffs are derivable, and 'strongly' if theses are maximised [Hughes/Cresswell] |
| Full Idea: To say that an axiom system is 'weakly complete' is to say that every valid wff of the system is derivable as a thesis. ..The system is 'strongly complete' if it cannot have any more theses than it has without falling into inconsistency. | |
| From: GE Hughes/M Cresswell (An Introduction to Modal Logic [1968], Ch.1) | |
| A reaction: [They go on to say that Propositional Logic is strongly complete, but Modal Logic is not] |
| 1556 | By nature people are close to one another, but culture drives them apart [Hippias] |
| Full Idea: I regard you all as relatives - by nature, not by convention. By nature like is akin to like, but convention is a tyrant over humankind and often constrains people to act contrary to nature. | |
| From: Hippias (fragments/reports [c.430 BCE]), quoted by Plato - Protagoras 337c8 |
| 23366 | We see nature's will in the ways all people are the same [Epictetus] |
| Full Idea: The will of nature may be learned from those things in which we do not differ from one another. | |
| From: Epictetus (The Handbook [Encheiridion] [c.58], 26) | |
| A reaction: There you go! This is the rule for anthropologists on field trips. And it guides us towards a core of essential human nature. But it neglects the way that nature is expressed in different cultures, which is also important. |
| 4022 | Epictetus says we should console others for misfortune, but not be moved by pity [Epictetus, by Taylor,C] |
| Full Idea: The injunction of Epictetus is well known, that in commiserating with another for his misfortune, we ought to talk consolingly, but not be moved by pity. | |
| From: report of Epictetus (The Handbook [Encheiridion] [c.58], §16) by Charles Taylor - Sources of the Self §15.1 | |
| A reaction: This goes strongly against the grain of the Christian tradition, but strikes me as an appealing attitude (even if I am the sufferer). |
| 23365 | If someone is weeping, you should sympathise and help, but not share his suffering [Epictetus] |
| Full Idea: When you see someone weeping is sorrow …do not shrink from sympathising with him, and even groaning with him, but be careful not to groan inwardly too. | |
| From: Epictetus (The Handbook [Encheiridion] [c.58], 16) | |
| A reaction: The point is that the person's suffering is an 'indifferent' because nothing can be done about it, and we should only really care about what we are able to choose. He is not opposed to the man's suffering, or his need for support. |
| 23368 | Perhaps we should persuade culprits that their punishment is just? [Epictetus] |
| Full Idea: The governor Agrippinus would try to persuade those whom he sentenced that it was proper for them to be sentenced, …just as the physician persuades a patient to accept their treatment. | |
| From: Epictetus (The Handbook [Encheiridion] [c.58], 22) | |
| A reaction: This resembles the Contractualism of T.H. Scanlon (that actions are good if you can justify them to those involved). It may be possible to persuade people by the use of sophistry and lies. Nevertheless, a fairly civilise proposal. |