20 ideas
| 5021 | An idea is analysed perfectly when it is shown a priori that it is possible [Leibniz] |
| Full Idea: Every idea is analysed perfectly only when it is demonstrated a priori that it is possible. | |
| From: Gottfried Leibniz (Of Organum or Ars Magna of Thinking [1679], p.3) | |
| A reaction: I take it he means metaphysical possibility, rather than natural, or we can't think about pigs flying. He probably has maths in mind. Seeing the possibility of something may well amount to understanding its truth conditions. |
| 192 | Only one thing can be contrary to something [Plato] |
| Full Idea: To everything that admits of a contrary there is one contrary and no more. | |
| From: Plato (Protagoras [c.380 BCE], 332c) | |
| A reaction: The sort of thing for which a modern philosopher would demand a proof (and then reject when the proof couldn't be found), where a Greek is happy to assert it as self-evident. I can't think of a counterexample. |
| 17896 | We need to know the meaning of 'and', prior to its role in reasoning [Prior,AN, by Belnap] |
| Full Idea: For Prior, so the moral goes, we must first have a notion of what 'and' means, independently of the role it plays as premise and as conclusion. | |
| From: report of Arthur N. Prior (The Runabout Inference Ticket [1960]) by Nuel D. Belnap - Tonk, Plonk and Plink p.132 | |
| A reaction: The meaning would be given by the truth tables (the truth-conditions), whereas the role would be given by the natural deduction introduction and elimination rules. This seems to be the basic debate about logical connectives. |
| 17898 | Prior's 'tonk' is inconsistent, since it allows the non-conservative inference A |- B [Belnap on Prior,AN] |
| Full Idea: Prior's definition of 'tonk' is inconsistent. It gives us an extension of our original characterisation of deducibility which is not conservative, since in the extension (but not the original) we have, for arbitrary A and B, A |- B. | |
| From: comment on Arthur N. Prior (The Runabout Inference Ticket [1960]) by Nuel D. Belnap - Tonk, Plonk and Plink p.135 | |
| A reaction: Belnap's idea is that connectives don't just rest on their rules, but also on the going concern of normal deduction. |
| 11021 | Prior rejected accounts of logical connectives by inference pattern, with 'tonk' his absurd example [Prior,AN, by Read] |
| Full Idea: Prior dislike the holism inherent in the claim that the meaning of a logical connective was determined by the inference patterns into which it validly fitted. ...His notorious example of 'tonk' (A → A-tonk-B → B) was a reductio of the view. | |
| From: report of Arthur N. Prior (The Runabout Inference Ticket [1960]) by Stephen Read - Thinking About Logic Ch.8 | |
| A reaction: [The view being attacked was attributed to Gentzen] |
| 13836 | Maybe introducing or defining logical connectives by rules of inference leads to absurdity [Prior,AN, by Hacking] |
| Full Idea: Prior intended 'tonk' (a connective which leads to absurdity) as a criticism of the very idea of introducing or defining logical connectives by rules of inference. | |
| From: report of Arthur N. Prior (The Runabout Inference Ticket [1960], §09) by Ian Hacking - What is Logic? |
| 190 | If asked whether justice itself is just or unjust, you would have to say that it is just [Plato] |
| Full Idea: If someone asked me 'Is justice itself just or unjust?' I should answer that it was just, wouldn't you? I agree. | |
| From: Plato (Protagoras [c.380 BCE], 330c) |
| 20184 | The only real evil is loss of knowledge [Plato] |
| Full Idea: The only real kind of faring ill is the loss of knowledge. | |
| From: Plato (Protagoras [c.380 BCE], 345b) | |
| A reaction: This must crucially involve the intellectualist view (of Socrates) that virtuos behaviour results from knowledge, and moral wickedness is the result of ignorance. It is hard to see how forgetting a phone number is evil. |
| 20185 | The most important things in life are wisdom and knowledge [Plato] |
| Full Idea: It would be shameful indeed to say that wisdom and knowledge are anything but the most powerful forces in human activity. | |
| From: Plato (Protagoras [c.380 BCE], 352d) | |
| A reaction: He lumps wisdom and knowledge together, and I think we can take 'knowledge' to mean something like understanding, because obviously mere atomistic propositional knowledge can be utterly trivial. |
| 5020 | Our thoughts are either dependent, or self-evident. All thoughts seem to end in the self-evident [Leibniz] |
| Full Idea: Whatever is thought by us is either conceived through itself, or involves the concept of another. …Thus one must proceed to infinity, or all thoughts are resolved into those which are conceived through themselves. | |
| From: Gottfried Leibniz (Of Organum or Ars Magna of Thinking [1679], p.1) | |
| A reaction: This seems to embody the rationalist attitude to foundations. I am sympathetic. Experiences just come to us as basic, but they don't qualify as 'thoughts', let alone knowledge. Experiences are more 'given' than 'conceptual'. |
| 191 | Everything resembles everything else up to a point [Plato] |
| Full Idea: Everything resembles everything else up to a point. | |
| From: Plato (Protagoras [c.380 BCE], 331d) |
| 203 | Courage is knowing what should or shouldn't be feared [Plato] |
| Full Idea: Knowledge of what is and is not to be feared is courage. | |
| From: Plato (Protagoras [c.380 BCE], 360d) |
| 202 | No one willingly and knowingly embraces evil [Plato] |
| Full Idea: No one willingly goes to meet evil, or what he thinks is evil. | |
| From: Plato (Protagoras [c.380 BCE], 358d) | |
| A reaction: Presumably people who actively choose satanism can override this deep-seated attitude. But their adherence to evil usually seems to be rather restrained. A danger of tautology with ideas like this. |
| 193 | Some things are good even though they are not beneficial to men [Plato] |
| Full Idea: 'Do you mean by good those things that are beneficial to men?' 'Not only those. I call some things which are not beneficial good as well'. | |
| From: Plato (Protagoras [c.380 BCE], 333e) | |
| A reaction: Examples needed, but this would be bad news for utilitarians. Good health is not seen as beneficial if it is taken for granted. Not being deaf. |
| 5019 | Supreme human happiness is the greatest possible increase of his perfection [Leibniz] |
| Full Idea: The supreme happiness of man consists in the greatest possible increase of his perfection. | |
| From: Gottfried Leibniz (Of Organum or Ars Magna of Thinking [1679], p.1) | |
| A reaction: I fear that (being a great intellectual) he had a rather intellectual interpretation of 'perfection'. This is in danger of being a tautology, but if the proposal is given an Aritotelian slant I am sympathetic. |
| 197 | Some pleasures are not good, and some pains are not evil [Plato] |
| Full Idea: There are some pleasures which are not good, and some pains which are not evil. | |
| From: Plato (Protagoras [c.380 BCE], 351d) | |
| A reaction: Sadism and child birth. Though Bentham (I think) says that there is nothing good about the pain, since the event would obviously be better without it. |
| 200 | People tend only to disapprove of pleasure if it leads to pain, or prevents future pleasure [Plato] |
| Full Idea: The only reason the common man disapproves of pleasures is if they lead to pain and deprive us of future pleasures. | |
| From: Plato (Protagoras [c.380 BCE], 354a) | |
| A reaction: Plato has a strong sense that some pleasures are just innately depraved and wicked. If those pleasure don't hurt anyone, it is very hard to pinpoint what is wrong with them. |
| 188 | Socrates did not believe that virtue could be taught [Plato] |
| Full Idea: Socrates: I do not believe that virtue can be taught. | |
| From: Plato (Protagoras [c.380 BCE], 320b) |
| 204 | Socrates is contradicting himself in claiming virtue can't be taught, but that it is knowledge [Plato] |
| Full Idea: Socrates is contradicting himself by saying virtue is not teachable, and yet trying to demonstrate that every virtue is knowledge. | |
| From: Plato (Protagoras [c.380 BCE], 361b) |
| 189 | If we punish wrong-doers, it shows that we believe virtue can be taught [Plato] |
| Full Idea: Athenians inflict punishment on wrong-doers, which shows that they too think it possible to impart and teach goodness. | |
| From: Plato (Protagoras [c.380 BCE], 324c) |