13 ideas
| 8658 | For there was never yet philosopher/ That could endure the toothache patiently [Shakespeare] |
| Full Idea: For there was never yet philosopher/ That could endure the toothache patiently. | |
| From: William Shakespeare (Much Ado About Nothing [1600], V.i) | |
| A reaction: You can't argue with that. I do think that people who have studied philosophy at length are more likely to be 'philosophical' when faced with human misery, but only up to a point. |
| 22708 | Good reasons must give way to better [Shakespeare] |
| Full Idea: Good reasons must of force give way to better. | |
| From: William Shakespeare (Julius Caesar [1599], 4.3.205) | |
| A reaction: [Brutus to Cassius] This remark is an axiom of rationality. But, of course, reasons can come in groups, and three modest reasons may compete with one very good reason. |
| 13913 | The four 'perfect syllogisms' are called Barbara, Celarent, Darii and Ferio [Engelbretsen/Sayward] |
| Full Idea: There are four 'perfect syllogisms': Barbara (every M is P, every S is M, so every S is P); Celarent (no M is P, every S is M, so no S is P); Darii (every M is P, some S is M, so some S is P); Ferio (no M is P, some S is M, so some S is not P). | |
| From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], 8) | |
| A reaction: The four names are mnemonics from medieval universities. |
| 13914 | Syllogistic logic has one rule: what is affirmed/denied of wholes is affirmed/denied of their parts [Engelbretsen/Sayward] |
| Full Idea: It has often been claimed (e.g. by Leibniz) that a single rule governs all syllogistic validity, called 'dictum de omni et null', which says that what is affirmed or denied of any whole is affirmed or denied of any part of that whole. | |
| From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], 8) | |
| A reaction: This seems to be the rule which is captured by Venn Diagrams. |
| 13915 | Syllogistic can't handle sentences with singular terms, or relational terms, or compound sentences [Engelbretsen/Sayward] |
| Full Idea: Three common kinds of sentence cannot be put into syllogistic ('categorical') form: ones using singular terms ('Mars is red'), ones using relational terms ('every painter owns some brushes'), and compound sentences. | |
| From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], 8) |
| 13916 | Term logic uses expression letters and brackets, and '-' for negative terms, and '+' for compound terms [Engelbretsen/Sayward] |
| Full Idea: Term logic begins with expressions and two 'term functors'. Any simple letter is a 'term', any term prefixed by a minus ('-') is a 'negative term', and any pair of terms flanking a plus ('+') is a 'compound term'. Parenthese are used for grouping. | |
| From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], 8) | |
| A reaction: [see Engelbretsen and Sayward for the full formal system] |
| 13850 | In modern logic all formal validity can be characterised syntactically [Engelbretsen/Sayward] |
| Full Idea: One of the key ideas of modern formal logic is that all formally valid inferences can be specified in strictly syntactic terms. | |
| From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], Ch.2) |
| 13849 | Classical logic rests on truth and models, where constructivist logic rests on defence and refutation [Engelbretsen/Sayward] |
| Full Idea: Classical logic rests on the concepts of truth and falsity (and usually makes use of a semantic theory based on models), whereas constructivist logic accounts for inference in terms of defense and refutation. | |
| From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], Intro) | |
| A reaction: My instincts go with the classical view, which is that inferences do not depend on the human capacity to defend them, but sit there awaiting revelation. My view isn't platonist, because I take the inferences to be rooted in the physical world. |
| 13851 | Unlike most other signs, = cannot be eliminated [Engelbretsen/Sayward] |
| Full Idea: Unlike ∨, →, ↔, and ∀, the sign = is not eliminable from a logic. | |
| From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], Ch.3) |
| 13852 | Axioms are ω-incomplete if the instances are all derivable, but the universal quantification isn't [Engelbretsen/Sayward] |
| Full Idea: A set of axioms is said to be ω-incomplete if, for some universal quantification, each of its instances is derivable from those axioms but the quantification is not thus derivable. | |
| From: Engelbretsen,G/Sayward,C (Philosophical Logic: Intro to Advanced Topics [2011], 7) |
| 3061 | Anaxarchus said that he was not even sure that he knew nothing [Anaxarchus, by Diog. Laertius] |
| Full Idea: Anaxarchus said that he was not even sure that he knew nothing. | |
| From: report of Anaxarchus (fragments/reports [c.340 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.10.1 |
| 20304 | The cause of my action is in my will [Shakespeare] |
| Full Idea: The cause is in my will. I will not come./That is enough to satisfy the senate./But for your private satisfaction,/Because I love you, I will let you know. | |
| From: William Shakespeare (Julius Caesar [1599], II.ii) | |
| A reaction: This asserts the purest form of volitionism, but then qualifies it, because Caesar's will has been influenced by his wife's dreams. |
| 23565 | Our obedience to the king erases any crimes we commit for him [Shakespeare] |
| Full Idea: We know enough if we know we are the king's men. Our obedience to the king wipes the crime of it out of us. | |
| From: William Shakespeare (Henry V [1599]), quoted by Michael Walzer - Just and Unjust Wars 03 | |
| A reaction: He is referring to the slaughter of the French servants behind the lines at Agincourt. A classic expression of 'I was just obeying orders', which was rejected at Nurnberg in 1946. Depends on the seriousness of the crime. |