15 ideas
| 23367 | Even pointing a finger should only be done for a reason [Epictetus] |
| Full Idea: Philosophy says it is not right even to stretch out a finger without some reason. | |
| From: Epictetus (fragments/reports [c.57], 15) | |
| A reaction: The key point here is that philosophy concerns action, an idea on which Epictetus is very keen. He rather despise theory. This idea perfectly sums up the concept of the wholly rational life (which no rational person would actually want to live!). |
| 14249 | Boolos reinterprets second-order logic as plural logic [Boolos, by Oliver/Smiley] |
| Full Idea: Boolos's conception of plural logic is as a reinterpretation of second-order logic. | |
| From: report of George Boolos (On Second-Order Logic [1975]) by Oliver,A/Smiley,T - What are Sets and What are they For? n5 | |
| A reaction: Oliver and Smiley don't accept this view, and champion plural reference differently (as, I think, some kind of metalinguistic device?). |
| 10830 | Second-order logic metatheory is set-theoretic, and second-order validity has set-theoretic problems [Boolos] |
| Full Idea: The metatheory of second-order logic is hopelessly set-theoretic, and the notion of second-order validity possesses many if not all of the epistemic debilities of the notion of set-theoretic truth. | |
| From: George Boolos (On Second-Order Logic [1975], p.45) | |
| A reaction: Epistemic problems arise when a logic is incomplete, because some of the so-called truths cannot be proved, and hence may be unreachable. This idea indicates Boolos's motivation for developing a theory of plural quantification. |
| 10829 | A sentence can't be a truth of logic if it asserts the existence of certain sets [Boolos] |
| Full Idea: One may be of the opinion that no sentence ought to be considered as a truth of logic if, no matter how it is interpreted, it asserts that there are sets of certain sorts. | |
| From: George Boolos (On Second-Order Logic [1975], p.44) | |
| A reaction: My intuition is that in no way should any proper logic assert the existence of anything at all. Presumably interpretations can assert the existence of numbers or sets, but we should be able to identify something which is 'pure' logic. Natural deduction? |
| 10832 | '∀x x=x' only means 'everything is identical to itself' if the range of 'everything' is fixed [Boolos] |
| Full Idea: One may say that '∀x x=x' means 'everything is identical to itself', but one must realise that one's answer has a determinate sense only if the reference (range) of 'everything' is fixed. | |
| From: George Boolos (On Second-Order Logic [1975], p.46) | |
| A reaction: This is the problem now discussed in the recent book 'Absolute Generality', of whether one can quantify without specifying a fixed or limited domain. |
| 10834 | Weak completeness: if it is valid, it is provable. Strong: it is provable from a set of sentences [Boolos] |
| Full Idea: A weak completeness theorem shows that a sentence is provable whenever it is valid; a strong theorem, that a sentence is provable from a set of sentences whenever it is a logical consequence of the set. | |
| From: George Boolos (On Second-Order Logic [1975], p.52) | |
| A reaction: So the weak version says |- φ → |= φ, and the strong versions says Γ |- φ → Γ |= φ. Presumably it is stronger if it can specify the source of the inference. |
| 13841 | Why should compactness be definitive of logic? [Boolos, by Hacking] |
| Full Idea: Boolos asks why on earth compactness, whatever its virtues, should be definitive of logic itself. | |
| From: report of George Boolos (On Second-Order Logic [1975]) by Ian Hacking - What is Logic? §13 |
| 10833 | Many concepts can only be expressed by second-order logic [Boolos] |
| Full Idea: The notions of infinity and countability can be characterized by second-order sentences, though not by first-order sentences (as compactness and Skolem-Löwenheim theorems show), .. as well as well-ordering, progression, ancestral and identity. | |
| From: George Boolos (On Second-Order Logic [1975], p.48) |
| 6237 | Fear of God is not conscience, which is a natural feeling of offence at bad behaviour [Shaftesbury] |
| Full Idea: Conscience is to find horribly offensive the reflection of any unjust action or behaviour; to have awe and terror of the Deity, does not, of itself, imply conscience; …thus religious conscience supposes moral or natural conscience. | |
| From: 3rd Earl of Shaftesbury (Inquiry Concerning Virtue or Merit [1699], II.II.I) | |
| A reaction: The reply from religion would be that the Deity has implanted natural conscience in each creature, though this seems to deny our freedom of moral judgment. Personally I am inclined to think that values are just observations of the world - such as health. |
| 6234 | If an irrational creature with kind feelings was suddenly given reason, its reason would approve of kind feelings [Shaftesbury] |
| Full Idea: If a creature wanting reason has many good qualities and affections, it is certain that if you give this creature a reflecting faculty, it will at the same instant approve of gratitude, kindness and pity. | |
| From: 3rd Earl of Shaftesbury (Inquiry Concerning Virtue or Merit [1699], I.III.III) | |
| A reaction: A wonderful denunciation of the authority of reason, which must have influenced David Hume. I think, though, that the inverse of this case must be considered (if suddenly given feelings, they would fall in line with reasoning). We reason about feelings. |
| 6233 | A person isn't good if only tying their hands prevents their mischief, so the affections decide a person's morality [Shaftesbury] |
| Full Idea: We do not say that he is a good man when, having his hands tied up, he is hindered from doing the mischief he designs; …hence it is by affection merely that a creature is esteemed good or ill, natural or unnatural. | |
| From: 3rd Earl of Shaftesbury (Inquiry Concerning Virtue or Merit [1699], I.II.I) | |
| A reaction: Note that he more or less equates being morally 'ill' with being 'unnatural'. We tend to reserve 'unnatural' for extreme or perverse crimes. Personally I would place more emphasis on evil judgements, and less on evil feelings. |
| 6236 | People more obviously enjoy social pleasures than they do eating and drinking [Shaftesbury] |
| Full Idea: How much the social pleasures are superior to any other may be known by visible tokens and effects; the marks and signs which attend this sort of joy are more intense and clear than those which attend the satisfaction of thirst and hunger. | |
| From: 3rd Earl of Shaftesbury (Inquiry Concerning Virtue or Merit [1699], II.II.I) | |
| A reaction: He presumably refers to smiles and laughter, but they could be misleading as they are partly a means of social communication. You should ask people whether they would prefer a nice conversation or a good pork chop. Nice point, though. |
| 6235 | Self-interest is not intrinsically good, but its absence is evil, as public good needs it [Shaftesbury] |
| Full Idea: Though no creature can be called good merely for possessing the self-preserving affections, it is impossible that public good can be preserved without them; so that a creature wanting in them is wanting in natural rectitude, and may be esteemed vicious. | |
| From: 3rd Earl of Shaftesbury (Inquiry Concerning Virtue or Merit [1699], II.I.III) | |
| A reaction: Aristotle held a similar view (Idea 92). I think maybe Shaftesbury was the last call of the Aristotelians, before being engulfed by utilitarians and Kantians. This idea is at the core of capitalism. |
| 6232 | Every creature has a right and a wrong state which guide its actions, so there must be a natural end [Shaftesbury] |
| Full Idea: We know there is a right and a wrong state of every creature; and that his right one is by nature forwarded, and by himself affectionately sought. There being therefore in every creature a certain interest or good; there must also be a natural end. | |
| From: 3rd Earl of Shaftesbury (Inquiry Concerning Virtue or Merit [1699], I.II.I) | |
| A reaction: This is an early modern statement of Aristotelian teleology, just at the point where it was falling out of fashion. The underlying concept is that of right function. I agree with Shaftesbury, but you can't stop someone damaging their health. |
| 5642 | For Shaftesbury, we must already have a conscience to be motivated to religious obedience [Shaftesbury, by Scruton] |
| Full Idea: Shaftesbury argued that no morality could be founded in religious obedience, or piety. On the contrary, a man is motivated to such obedience only because conscience tells him that the divine being is worthy of it. | |
| From: report of 3rd Earl of Shaftesbury (Inquiry Concerning Virtue or Merit [1699]) by Roger Scruton - Short History of Modern Philosophy Ch.8 | |
| A reaction: This seems to me a good argument. The only alternative is that we are brought to God by a conscience which was planted in us by God, but then how would you know you were being obedient to the right hypnotist? |