Combining Texts

All the ideas for 'On the Philosophy of Logic', 'Symposium' and 'The Problem of Possibilia'

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13 ideas

2. Reason / A. Nature of Reason / 1. On Reason
8952 We reach 'reflective equilibrium' when intuitions and theory completely align [Fisher]
     Full Idea: A state of 'reflective equilibrium' is when our theory and our intuitions become completely aligned
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 12.IV)
     A reaction: [Rawls made this concept famous] This is a helpful concept in trying to spell out the ideal which is the dream of believers in 'pure reason' - that there is a goal in which everything comes right. The problem is when people have different intuitions!
4. Formal Logic / E. Nonclassical Logics / 3. Many-Valued Logic
8943 Three-valued logic says excluded middle and non-contradition are not tautologies [Fisher]
     Full Idea: In three-valued logic (L3), neither the law of excluded middle (p or not-p), nor the law of non-contradiction (not(p and not-p)) will be tautologies. If p has the value 'indeterminate' then so will not-p.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.I)
     A reaction: I quite accept that the world is full of indeterminate propositions, and that excluded middle and non-contradiction can sometimes be uncertain, but I am reluctant to accept that what is being offered here should be called 'logic'.
4. Formal Logic / E. Nonclassical Logics / 4. Fuzzy Logic
8945 Fuzzy logic has many truth values, ranging in fractions from 0 to 1 [Fisher]
     Full Idea: In fuzzy logic objects have properties to a greater or lesser degree, and truth values are given as fractions or decimals, ranging from 0 to 1. Not-p is defined as 1-p, and other formula are defined in terms of maxima and minima for sets.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.II)
     A reaction: The question seems to be whether this is actually logic, or a recasting of probability theory. Susan Haack attacks it. If logic is the study of how truth is preserved as we move between propositions, then 0 and 1 need a special status.
5. Theory of Logic / A. Overview of Logic / 6. Classical Logic
8951 Classical logic is: excluded middle, non-contradiction, contradictions imply all, disjunctive syllogism [Fisher]
     Full Idea: For simplicity, we can say that 'classical logic' amounts to the truth of four sentences: 1) either p or not-p; 2) it is not the case that both p and not-p; 3) from p and not-p, infer q; 4) from p or q and not-p, infer q.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 12.I)
     A reaction: [She says there are many ways of specifying classical logic] Intuition suggests that 2 and 4 are rather hard to dispute, while 1 is ignoring some grey areas, and 3 is totally ridiculous. There is, of course, plenty of support for 3!
5. Theory of Logic / C. Ontology of Logic / 2. Platonism in Logic
8950 Logic formalizes how we should reason, but it shouldn't determine whether we are realists [Fisher]
     Full Idea: Even if one is inclined to be a realist about everything, it is hard to see why our logic should be the determiner. Logic is supposed to formalize how we ought to reason, but whether or not we should be realists is a matter of philosophy, not logic.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 09.I)
     A reaction: Nice to hear a logician saying this. I do not see why talk in terms of an object is a commitment to its existence. We can discuss the philosopher's stone, or Arthur's sword, or the Loch Ness monster, or gravitinos, with degrees of commitment.
7. Existence / D. Theories of Reality / 10. Vagueness / g. Degrees of vagueness
8946 We could make our intuitions about heaps precise with a million-valued logic [Fisher]
     Full Idea: We could construct a 1,000,000-valued logic that would allow our intuitions concerning a heap to vary exactly with the amount of sand in the heap.
     From: Jennifer Fisher (On the Philosophy of Logic [2008])
     A reaction: Presumably only an infinite number of grains of sand would then produce a true heap, and even one grain would count as a bit of a heap, which must both be wrong, so I can't see this helping much.
9. Objects / B. Unity of Objects / 3. Unity Problems / e. Vague objects
8944 Vagueness can involve components (like baldness), or not (like boredom) [Fisher]
     Full Idea: Vague terms come in at least two different kinds: those whose constituent parts come in discrete packets (bald, rich, red) and those that don't (beauty, boredom, niceness).
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.II)
     A reaction: The first group seem to be features of the external world, and the second all occur in the mind. Baldness may be vague, but presumably hairs are (on the whole) not. Nature doesn't care whether someone is actually 'bald' or not.
10. Modality / B. Possibility / 1. Possibility
9212 Possible states of affairs are not propositions; a proposition can't be a state of affairs! [Fine,K]
     Full Idea: Possible states of affairs have often been taken to be propositions, but this cannot be correct, since any possible state of affairs is possibly a state of affairs, but no proposition is possibly a state of affairs.
     From: Kit Fine (The Problem of Possibilia [2003], 2)
     A reaction: The point is, presumably, that the state of affairs cannot be the proposition itself, but (at least) what the proposition refers to. I can't see any objection to that.
8941 We can't explain 'possibility' in terms of 'possible' worlds [Fisher]
     Full Idea: Explaining 'it is possible that p' by saying p is true in at least one possible world doesn't get me very far. If I don't understand what possibility is, then appealing to possible worlds is not going to do me much good.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 06.III)
     A reaction: This seems so blatant that I assume friends of possible worlds will have addressed the problem. Note that you will also need to understand 'possible' to define necessity as 'true in all possible worlds'. Necessarily-p is not-possibly-not-p.
10. Modality / B. Possibility / 8. Conditionals / c. Truth-function conditionals
8947 If all truths are implied by a falsehood, then not-p might imply both q and not-q [Fisher]
     Full Idea: If all truths are implied by a falsehood, then 'if there are no trees in the park then there is no shade' and 'if there are no trees in the park there is plenty of shade' both come out as true. Intuitively, though, the second one is false.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 08.I)
     A reaction: The rule that a falsehood implies all truths must be the weakest idea in classical logic, if it actually implies a contradiction. This means we must take an interest in relevance logics.
10. Modality / B. Possibility / 8. Conditionals / d. Non-truthfunction conditionals
8949 In relevance logic, conditionals help information to flow from antecedent to consequent [Fisher]
     Full Idea: A good account of relevance logic suggests that a conditional will be true when the flow of information is such that a conditional is the device that helps information to flow from the antecedent to the consequent.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 08.III)
     A reaction: Hm. 'If you are going out, you'll need an umbrella'. This passes on information about 'out', but also brings in new information. 'If you are going out, I'm leaving you'. What flows is an interpretation of the antecedent. Tricky.
10. Modality / E. Possible worlds / 2. Nature of Possible Worlds / a. Nature of possible worlds
9213 The actual world is a possible world, so we can't define possible worlds as 'what might have been' [Fine,K]
     Full Idea: A possible world can't be defined (by Stalnaker and Plantinga) as a way the world might have been, because a possible world is possibly the world, yet no way the world might have been is possibly the world.
     From: Kit Fine (The Problem of Possibilia [2003], 2)
     A reaction: His point is that any definition of a possible world must cover the actual world, because that is one of them. 'Might have been' is not applicable to the actual world. It seems a fairly important starting point for discussion of possible worlds.
22. Metaethics / B. Value / 2. Values / h. Fine deeds
5845 Niceratus learnt the whole of Homer by heart, as a guide to goodness [Xenophon]
     Full Idea: Niceratus said that his father, because he was concerned to make him a good man, made him learn the whole works of Homer, and he could still repeat by heart the entire 'Iliad' and 'Odyssey'.
     From: Xenophon (Symposium [c.391 BCE], 3.5)
     A reaction: This clearly shows the status which Homer had in the teaching of morality in the time of Socrates, and it is precisely this acceptance of authority which he was challenging, in his attempts to analyse the true basis of virtue