29 ideas
| 1922 | Spiritual qualities only become advantageous with the growth of wisdom [Plato] |
| Full Idea: If virtue is a beneficial attribute of spirit, it must be wisdom; for spiritual qualities are not in themselves advantageous, but become so with wisdom…..Hence men cannot be good by nature. | |
| From: Plato (Meno [c.385 BCE], 88c) | |
| A reaction: Personally I haven't got any 'spiritual qualities', so I don't really understand this. |
| 10688 | 'Equivocation' is when terms do not mean the same thing in premises and conclusion [Beall/Restall] |
| Full Idea: 'Equivocation' is when the terms do not mean the same thing in the premises and in the conclusion. | |
| From: JC Beall / G Restall (Logical Consequence [2005], Intro) |
| 10690 | Formal logic is invariant under permutations, or devoid of content, or gives the norms for thought [Beall/Restall] |
| Full Idea: Logic is purely formal either when it is invariant under permutation of object (Tarski), or when it has totally abstracted away from all contents, or it is the constitutive norms for thought. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 2) | |
| A reaction: [compressed] The third account sounds rather woolly, and the second one sounds like a tricky operation, but the first one sounds clear and decisive, so I vote for Tarski. |
| 10691 | Logical consequence needs either proofs, or absence of counterexamples [Beall/Restall] |
| Full Idea: Technical work on logical consequence has either focused on proofs, where validity is the existence of a proof of the conclusions from the premises, or on models, which focus on the absence of counterexamples. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 3) |
| 10695 | Logical consequence is either necessary truth preservation, or preservation based on interpretation [Beall/Restall] |
| Full Idea: Two different views of logical consequence are necessary truth-preservation (based on modelling possible worlds; favoured by Realists), or truth-preservation based on the meanings of the logical vocabulary (differing in various models; for Anti-Realists). | |
| From: JC Beall / G Restall (Logical Consequence [2005], 2) | |
| A reaction: Thus Dummett prefers the second view, because the law of excluded middle is optional. My instincts are with the first one. |
| 10689 | A step is a 'material consequence' if we need contents as well as form [Beall/Restall] |
| Full Idea: A logical step is a 'material consequence' and not a formal one, if we need the contents as well as the structure or form. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 2) |
| 10696 | A 'logical truth' (or 'tautology', or 'theorem') follows from empty premises [Beall/Restall] |
| Full Idea: If a conclusion follows from an empty collection of premises, it is true by logic alone, and is a 'logical truth' (sometimes a 'tautology'), or, in the proof-centred approach, 'theorems'. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 4) | |
| A reaction: These truths are written as following from the empty set Φ. They are just implications derived from the axioms and the rules. |
| 10693 | Models are mathematical structures which interpret the non-logical primitives [Beall/Restall] |
| Full Idea: Models are abstract mathematical structures that provide possible interpretations for each of the non-logical primitives in a formal language. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 3) |
| 11259 | How can you seek knowledge of something if you don't know it? [Plato] |
| Full Idea: How will you aim to search for something you do not know at all? If you should meet with it, how will you know that this is the thing that you did not know? | |
| From: Plato (Meno [c.385 BCE], 80d05) | |
| A reaction: Vasilis Politis cites this as a nice example of the 'aporiai' (puzzles) which Aristotle said were the foundation of enquiry. Nowadays the problem is called the 'paradox of enquiry'. |
| 10692 | Hilbert proofs have simple rules and complex axioms, and natural deduction is the opposite [Beall/Restall] |
| Full Idea: There are many proof-systems, the main being Hilbert proofs (with simple rules and complex axioms), or natural deduction systems (with few axioms and many rules, and the rules constitute the meaning of the connectives). | |
| From: JC Beall / G Restall (Logical Consequence [2005], 3) |
| 20219 | True opinions only become really valuable when they are tied down by reasons [Plato] |
| Full Idea: True opinions are a fine thing and all they do is good, …but they escape from a man's mind, so they are not worth much until one ties them down by (giving) an account of the reason why. | |
| From: Plato (Meno [c.385 BCE], 98a3) | |
| A reaction: This gives justification the role of guarantee, stabilising and securing true beliefs (rather than triggering some new thing called 'knowledge'). |
| 5985 | Seeking and learning are just recollection [Plato] |
| Full Idea: Seeking and learning are in fact nothing but recollection. | |
| From: Plato (Meno [c.385 BCE], 81d) | |
| A reaction: This is a prelude to the famous conversation with the slave boy about geometry. You don't have to follow Plato into the doctrine of reincarnation; this remark is a key slogan for all rationalists. As pupils in maths lessons, we pull knowledge from within. |
| 5986 | The slave boy learns geometry from questioning, not teaching, so it is recollection [Plato] |
| Full Idea: The slave boy's knowledge of geometry will not come from teaching but from questioning; he will recover it for himself, and the spontaneous recovery of knowledge that is in him is recollection. | |
| From: Plato (Meno [c.385 BCE], 85d) | |
| A reaction: Of course, if maths and geometry are huge tautological axiom systems, we would expect to be able to derive them (with hints from a teacher) entirely from their axioms. It is not clear why we might be able to derive the truths of all nature a priori. |
| 1923 | As a guide to action, true opinion is as good as knowledge [Plato] |
| Full Idea: True opinion is as good a guide as knowledge for the purpose of acting rightly. | |
| From: Plato (Meno [c.385 BCE], 97b) | |
| A reaction: This is the germ of Peirce's epistemology - that knowledge is an interesting theoretical concept, but opinion/belief is what matters, and most needs explanation. |
| 1919 | You don't need to learn what you know, and how do you seek for what you don't know? [Plato] |
| Full Idea: You could argue that a man cannot discover what he does know or what he doesn't. The first needs no discovery, and how do you begin looking for the second? | |
| From: Plato (Meno [c.385 BCE], 80e) |
| 21740 | I doubt whether ethics is part of philosophy [Russell] |
| Full Idea: I hardly think myself that ethics ought to be included in the domain of philosophy. | |
| From: Bertrand Russell (An Outline of Philosophy [1927], Ch.22) | |
| A reaction: He declines to give his reasons. The implication of the chapter is that ethics is essentially a social and political matter, so that individual ethical guidelines are unimportant. Maybe the woolliness of ethics was also an impediment. |
| 21741 | 'You ought to do p' primarily has emotional content, expressing approval [Russell] |
| Full Idea: A sentence like 'You ought to do so-and-so' primarily has an emotional content. It means ' this is the act towards which I feel the emotion of approval'. | |
| From: Bertrand Russell (An Outline of Philosophy [1927], Ch 22) | |
| A reaction: I don't understand how I can say 'you ought to do p', and very clearly mean that the situation would be altogether better if p, only to be told by some philosopher that what I thought was a sensible judgement is actually an emotional outburst. |
| 21746 | Unlike hate, all desires can be satisfied by love [Russell] |
| Full Idea: If harmonious desires are what we should seek, love is better than hate, since, when two people love each other, both can be satisfied, whereas when they hate each other one at most can achieve the object of his desire. | |
| From: Bertrand Russell (An Outline of Philosophy [1927], Ch 22) | |
| A reaction: A wonderful example of cool philosophical objectivity! Of course it is not true, because the fact that two people love one another doesn't not prevent them from having some incompatible desires, as every couple knows. |
| 21747 | Goodness is a combination of love and knowledge [Russell] |
| Full Idea: The good life is one inspired by love and guided by knowledge. | |
| From: Bertrand Russell (An Outline of Philosophy [1927], Ch 22) | |
| A reaction: Forty years later, Russell's famous filmed message to posteriority said exactly this. In decision making, get the facts; in relationships, show love and tolerance. I find both parts inspiring. |
| 21743 | In wartime, happiness is hating the enemy, because it gives the war a purpose [Russell] |
| Full Idea: During and immediately after the war [14-18], those who hated the Germans were happier than those who still regarded them as human beings, because they could feel that what was being done served a good purpose. | |
| From: Bertrand Russell (An Outline of Philosophy [1927], Ch 22) | |
| A reaction: A striking remark. There are lots of situations where hatred seems to increase happiness. Russell is roughly defending consequentialism. |
| 21742 | Originally virtue was obedience, to gods, government, or custom [Russell] |
| Full Idea: Historically, virtue consisted at first of obedience to authority, whether that of the gods, the government, or custom. | |
| From: Bertrand Russell (An Outline of Philosophy [1927], Ch 22) | |
| A reaction: Russell proceeds to demolish such a theory, which he finds it fairly easy to do. In Nietzsche's terms, he is only describing slave virtue. Each role in the world has its own virtues (and functions). Which gods are the most virtuous? |
| 1913 | Is virtue taught, or achieved by practice, or a natural aptitude, or what? [Plato] |
| Full Idea: Is virtue something that can be taught, or does it come by practice, or is it a natural aptitude, or something else? | |
| From: Plato (Meno [c.385 BCE], 70a) |
| 1921 | If virtue is a type of knowledge then it ought to be taught [Plato] |
| Full Idea: If virtue is some sort of knowledge, then clearly it could be taught. | |
| From: Plato (Meno [c.385 BCE], 87c) |
| 1927 | It seems that virtue is neither natural nor taught, but is a divine gift [Plato] |
| Full Idea: If our discussion is right, virtue is acquired neither by nature nor by teaching. Whoever has it gets it by divine dispensation, without taking thought. | |
| From: Plato (Meno [c.385 BCE], 99e) |
| 1918 | How can you know part of virtue without knowing the whole? [Plato] |
| Full Idea: Does anyone know what a part of virtue is without knowing the whole? | |
| From: Plato (Meno [c.385 BCE], 79c) |
| 1916 | Even if virtues are many and various, they must have something in common to make them virtues [Plato] |
| Full Idea: Even if virtues are many and various, at least they all have some common character which makes them all virtues. | |
| From: Plato (Meno [c.385 BCE], 72c) |
| 21745 | Act so as to produce harmonious rather than discordant desires [Russell] |
| Full Idea: The supreme moral rule should be: Act so as to produce harmonious rather than discordant desires. | |
| From: Bertrand Russell (An Outline of Philosophy [1927], Ch 22) | |
| A reaction: Russell makes no reference to Kant, but this is obviously intended to rebut the more rationalist Kantian view of what is imperative. The use of 'harmonious' chimes in best with Plato's account of the soul in 'Republic'. |
| 21744 | Legally curbing people's desires is inferior to improving their desires [Russell] |
| Full Idea: To force a man to curb his desires, as we do by the criminal law, is not nearly so satisfactory as to cause him genuinely to feel the desires which promote socially harmonious conduct. | |
| From: Bertrand Russell (An Outline of Philosophy [1927], Ch 22) | |
| A reaction: It is hard to disagree, but improving the desires of selfish and even vicious people is a rather challenging task. |
| 22891 | We could be aware of time if senses briefly vibrated, extending their experience of movement [Russell, by Bardon] |
| Full Idea: Russell suggested, in defence of an empiricist theory of time-awareness, that a sense organ goes on vibrating, like a piano string, for while after the stimulation. Thus we can see the movement of a second hand, seen in several places at once. | |
| From: report of Bertrand Russell (An Outline of Philosophy [1927]) by Adrian Bardon - Brief History of the Philosophy of Time 2 'Realism' | |
| A reaction: Hm. If they were vibrating the last experience, they couldn't pick up the new one. When something fast happens the brain resonates fortissimo! If your eyes are moving it will be different neurons that get fired at each instant. |