12 ideas
19695 | The devil was wise as an angel, and lost no knowledge when he rebelled [Whitcomb] |
Full Idea: The devil is evil but nonetheless wise; he was a wise angel, and through no loss of knowledge, but, rather, through some sort of affective restructuring tried and failed to take over the throne. | |
From: Dennis Whitcomb (Wisdom [2011], 'Argument') | |
A reaction: ['affective restructuring' indeed! philosophers- don't you love 'em?] To fail at something you try to do suggests a flaw in the wisdom. And the new regime the devil wished to introduce doesn't look like a wise regime. Not convinced. |
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] |
13437 | A CAR and its major PART can become identical, yet seem to have different properties [Gallois] |
Full Idea: At t1 there is a whole CAR, and a PART of it, which is everything except the right front wheel. At t2 the wheel is removed, leaving just PART, so that CAR is now PART. But PART was a proper part of CAR, and CAR had the front wheel. Different properties! | |
From: André Gallois (Occasions of Identity [1998], 1.II) | |
A reaction: [compressed summary] The problem is generated by appealing to Leibniz's Law. My immediate reaction is that this is the sort of trouble you get into if you include such temporal truths about things as 'properties'. |
16233 | Gallois hoped to clarify identity through time, but seems to make talk of it impossible [Hawley on Gallois] |
Full Idea: A problem for Gallois is that he leaves us no way to talk about questions of genuine identity through time, and thus undercuts one motivation for his own position. | |
From: comment on André Gallois (Occasions of Identity [1998]) by Katherine Hawley - How Things Persist 5.8 | |
A reaction: Gallois seems to need a second theory of identity to support his Occasional Identity theory. Two things need an identity each, before we can say that the two identities coincide. (Time to read Gallois!) |
16025 | If things change they become different - but then no one thing undergoes the change! [Gallois] |
Full Idea: If things really change, there can't literally be one thing before and after the change. However, if there isn't one thing before and after the change, then no thing has really undergone any change. | |
From: André Gallois (Identity over Time [2011], Intro) | |
A reaction: [He cites Copi for this way of expressing the problem of identity through change] There is an obvious simple ambiguity about 'change' in ordinary English. A change of property isn't a change of object. Painting a red ball blue isn't swapping it. |
16026 | 4D: time is space-like; a thing is its history; past and future are real; or things extend in time [Gallois] |
Full Idea: We have four versions of Four-Dimensionalism: the relativistic view that time is space-like; a persisting thing is identical with its history (so objects are events); past and future are equally real; or (Lewis) things extend in time, with temporal parts. | |
From: André Gallois (Identity over Time [2011], §2.5) | |
A reaction: Broad proposed the second one. I prefer 3-D: at any given time a thing is wholly present. At another time it is wholly present despite having changed. It is ridiculous to think that small changes destroy identity. We acquire identity by dying?? |
14755 | Gallois is committed to identity with respect to times, and denial of simple identity [Gallois, by Sider] |
Full Idea: Gallois's core claim is that the identity relation holds with respect to times, ...and he must claim that there is no such thing as the relation of identity simpliciter. | |
From: report of André Gallois (Occasions of Identity [1998]) by Theodore Sider - Four Dimensionalism 5.5 | |
A reaction: Gallois is essentially responding to the statue and clay problem, but it seems a bit drastic to entirely change our concept of two things being identical, such as Hesperus and Phosphorus. 'Identity' seems to have several meanings; let's sort them out. |
16231 | Occasional Identity: two objects can be identical at one time, and different at others [Gallois, by Hawley] |
Full Idea: Gallois' Occasional Identity Thesis is that objects can be identical at one time without being identical at all times. | |
From: report of André Gallois (Occasions of Identity [1998]) by Katherine Hawley - How Things Persist 5.4 | |
A reaction: The analogy is presumably with two crossing roads being identical at one place but not at others. It is a major misunderstanding to infer from Special Relativity that time is just like space. |
16027 | If two things are equal, each side involves a necessity, so the equality is necessary [Gallois] |
Full Idea: The necessity of identity: a=b; □(a=a); so something necessarily = a; so something necessarily must equal b; so □(a=b). [A summary of the argument of Marcus and Kripke] | |
From: André Gallois (Identity over Time [2011], §3) | |
A reaction: [Lowe 1982 offered a response] The conclusion seems reasonable. If two things are mistakenly thought to be different, but turn out to be one thing, that one thing could not possibly be two things. In no world is one thing two things! |