| 16728 | Logicians acknowledge too few things, while others acknowledge too many [Fitzralph] |
| Full Idea: Those who have been well trained in logic err in recognising too few things, whereas others who are ignorant of logic ascribe to every statement a new entity, postulating more entities than God has ever established as real. | |
| From: Richard Fitzralph (Sentences [1328], II.1.2), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 22.3 |
| 12992 | Logic teaches us how to order and connect our thoughts [Leibniz] |
| Full Idea: Logic teaches us how to order and connect our thoughts. | |
| From: Gottfried Leibniz (New Essays on Human Understanding [1704], 3.10) | |
| A reaction: Leibniz had a higher opinion of logic than contemporaries like Locke. The question is whether logic can actually teach us better order than we could otherwise manage, or whether it just describes what most thinkers do. |
| 22275 | Logic gives us the necessary rules which show us how we ought to think [Kant] |
| Full Idea: In logic the question is not one of contingent but of necessary rules, not how to think, but how we ought to think. | |
| From: Immanuel Kant (Wiener Logik [1795], p.16), quoted by Michael Potter - The Rise of Analytic Philosophy 1879-1930 02 'Trans' | |
| A reaction: Presumably it aspires to the objectivity of a single correct account of how we all ought to think. I'm sympathetic to that, rather than modern cultural relativism about reason. Logic is rooted in nature, not in arbitrary convention. |
| 14780 | Only study logic if you think your own reasoning is deficient [Peirce] |
| Full Idea: It is foolish to study logic unless one is persuaded that one's own reasonings are more or less bad. | |
| From: Charles Sanders Peirce (Criterion of Validity in Reasoning [1903], II) |
| 7188 | Logic tries to understand the world according to a man-made scheme [Nietzsche] |
| Full Idea: Logic is the attempt to understand the real world according to a scheme of being that we have posited. | |
| From: Friedrich Nietzsche (Writings from Late Notebooks [1887], 09[97]) | |
| A reaction: This is the ruthless relativist trying to relativise the holy-of-holies, pure logic. I don't believe it. Once you allow counting, identity and sets, based on types, (and why not?) then logic follows. |
| 7145 | Logic is not driven by truth, but desire for a simple single viewpoint [Nietzsche] |
| Full Idea: In logic a drive rules, first of falsifying, and then of implementing a single viewpoint: logic does not originate in the will to truth. | |
| From: Friedrich Nietzsche (Writings from Late Notebooks [1887], 40[13]) | |
| A reaction: Presumably logic derives from a will to simplify rather than a will for truth. Ockham's Razor describes the essence of human thinking. Even if Nietzsche is right, there is still a desire that the simplified view should be true. |
| 7144 | Logic must falsely assume that identical cases exist [Nietzsche] |
| Full Idea: Logic assumes identical cases exist; to think and conclude logically, the fulfilment of this condition must first be feigned. That is: the will to logical truth cannot realise itself until a fundamental falsification of all events has been undertaken. | |
| From: Friedrich Nietzsche (Writings from Late Notebooks [1887], 40[13]) | |
| A reaction: Interesting. This implies that the particularism espoused by virtue theorists (there are no principles, as each case is slightly different) should be extended to other branches of human understanding. So arithmetic is impossible?? |
| 16867 | Logic not only proves things, but also reveals logical relations between them [Frege] |
| Full Idea: A proof does not only serve to convince us of the truth of what is proved: it also serves to reveal logical relations between truths. Hence we find in Euclid proofs of truths that appear to stand in no need of proof because they are obvious without one. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.204) | |
| A reaction: This is a key idea in Frege's philosophy, and a reason why he is the founder of modern analytic philosophy, with logic placed at the centre of the subject. I take the value of proofs to be raising questions, more than giving answers. |
| 14880 | Logic is just slavery to language [Nietzsche] |
| Full Idea: Logic is merely slavery in the fetters of language. | |
| From: Friedrich Nietzsche (Unpublished Notebooks 1872-74 [1873], 29 [008]) | |
| A reaction: I don't think I agree with this, but I still like it. |
| 9179 | Frege frequently expressed a contempt for language [Frege, by Dummett] |
| Full Idea: Frege frequently expressed a contempt for language. | |
| From: report of Gottlob Frege (works [1890], p.228) by Michael Dummett - Frege's Distinction of Sense and Reference p.228 | |
| A reaction: This strikes me as exactly the right attitude for a logician to have. Russell seems to have agreed. Attitudes to vagueness are the test case. Over-ambitious modern logicians dream of dealing with vagueness. Forget it. Stick to your last. |
| 21588 | Logic gives the method of research in philosophy [Russell] |
| Full Idea: Logic gives the method of research in philosophy, just as mathematics gives the method in physics. | |
| From: Bertrand Russell (Our Knowledge of the External World [1914], 8) | |
| A reaction: I'm struck by how rarely philosophers actually prove anything. Mostly they just use the language of logic as a tool for disambiguation. Only a tiny handful of philosophers can actually create sustained and novel proofs. |
| 6107 | It is logic, not metaphysics, that is fundamental to philosophy [Russell] |
| Full Idea: I hold that logic is what is fundamental in philosophy, and that schools should be characterised rather by their logic than by their metaphysics. | |
| From: Bertrand Russell (Logical Atomism [1924], p.143) | |
| A reaction: Personally I disagree. Russell seems to have been most interested in the logical form underlying language, but that seems to be because he was interested in the ontological implications of what we say, which is metaphysics. |
| 10152 | Set theory and logic are fairy tales, but still worth studying [Tarski] |
| Full Idea: People have asked me, 'How can you, a nominalist, do work in set theory and in logic, which are theories about things you do not believe in?' ...I believe that there is a value even in fairy tales and the study of fairy tales. | |
| From: Alfred Tarski (talk [1965]), quoted by Feferman / Feferman - Alfred Tarski: life and logic | |
| A reaction: This is obviously an oversimplification. I don't think for a moment that Tarski literally believed that the study of fairy tales had as much value as the study of logic. Why do we have this particular logic, and not some other? |
| 6428 | Wittgenstein is right that logic is just tautologies [Wittgenstein, by Russell] |
| Full Idea: I think Wittgenstein is right when he says (in the 'Tractatus') that logic consists wholly of tautologies. | |
| From: report of Ludwig Wittgenstein (Tractatus Logico-Philosophicus [1921]) by Bertrand Russell - My Philosophical Development Ch.10 | |
| A reaction: Despite Russell's support, I find this hard to accept. While a 'pure' or 'Platonist' logic may be hard to demonstrate or believe, I have a strong gut feeling that logic is more of a natural phenomenon than a human convention. |
| 9028 | Maybe logical truth reflects reality, but in different ways in different languages [Quine] |
| Full Idea: Perhaps the logical truths owe their truth to certain traits of reality which are reflected in one way by the grammar of our language, in another way by the grammar of another language, and in a third way by the grammar and lexicon of a third language. | |
| From: Willard Quine (Philosophy of Logic [1970], Ch.7) | |
| A reaction: This explains Quine's subsequent interest in translation, and the interest of his pupil Davidson in charity, and whether there could actually be rival conceptual schemes. I like the link between logical truths and reality, which follows Russell. |
| 9244 | Logic is easy, but what about logic to the point of death? [Camus] |
| Full Idea: It is always easy to be logical. It is almost impossible to be logical to the bitter end. The only problem that interests me is: is there a logic to the point of death? | |
| From: Albert Camus (The Myth of Sisyphus [1942], 'Abs and Suic') | |
| A reaction: This is a lovely hand grenade to lob into an analytical logic class! It is very hard to get logicians to actually ascribe a clear value to their activity. They tend to present it as a marginal private game, and yet it has high status. |
| 8219 | Logic has an infantile idea of philosophy [Deleuze/Guattari] |
| Full Idea: Logic has an infantile idea of philosophy. | |
| From: G Deleuze / F Guattari (What is Philosophy? [1991], 1.1) | |
| A reaction: This offers some explanation of why Anglo-American philosophers are steeped in logic, and the continentals just ignore it. I have some sympathy with the French view. Logic seems to study language with all the interesting part drained off. |
| 8246 | Logic hates philosophy, and wishes to supplant it [Deleuze/Guattari] |
| Full Idea: A real hatred inspires logic's rivalry with, or its will to supplant, philosophy. | |
| From: G Deleuze / F Guattari (What is Philosophy? [1991], 2.6) | |
| A reaction: A delightful corrective to the neurotic inferiority that most English-speaking philosophers feel about their failure to master logic. What was Aristotle playing at when he invented logic? Philosophical talent is utterly different from a talent for logic. |
| 13479 | Given that thinking aims at truth, logic gives universal rules for how to do it [Burge] |
| Full Idea: The laws of logic - which are constituted by atemporal thoughts and atemporal subject matter - provide universal prescriptions of how one ought to think, given that one's thinking has the function of attaining truth. | |
| From: Tyler Burge (Frege on Knowing the Third Realm [1992], p.316) | |
| A reaction: Burge is giving, and endorsing, Frege's view. Burge is fighting a rearguard action, when logical systems keep proliferating. See Idea 10282. I sympathise with the dream of Burge and Frege. |
| 3599 | Deduction shows entailments, not what to believe [Williams,M] |
| Full Idea: The rules of deduction are rules of entailment, not rules of inference. They tell us what follows from what, not what to believe on the basis of what. | |
| From: Michael Williams (Problems of Knowledge [2001], Ch.18) |
| 13378 | It is a mistake to think that the logic developed for mathematics can clarify language and philosophy [Jubien] |
| Full Idea: It has often been uncritically assumed that logic that was initially a tool for clarifying mathematics could be seamlessly and uniformly applied in the effort to clarify ordinary language and philosophy, but this has been a real mistake. | |
| From: Michael Jubien (Possibility [2009], Intro) | |
| A reaction: I'm not saying he's right (since you need stupendous expertise to make that call) but my intuitions are that he has a good point, and he is at least addressing a crucial question which most analytical philosophers avert their eyes from. |
| 6858 | Formal logic struck me as exactly the language I wanted to think in [Williamson] |
| Full Idea: As soon as I started learning formal logic, that struck me as exactly the language that I wanted to think in. | |
| From: Timothy Williamson (Interview with Baggini and Stangroom [2001]) | |
| A reaction: It takes all sorts… It is interesting that formal logic might be seen as having the capacity to live up to such an aspiration. I don't think the dream of an ideal formal language is dead, though it will never encompass all of reality. Poetic truth. |
| 9390 | Logic guides thinking, but it isn't a substitute for it [Rumfitt] |
| Full Idea: Logic is part of a normative theory of thinking, not a substitute for thinking. | |
| From: Ian Rumfitt (The Logic of Boundaryless Concepts [2007], p.13) | |
| A reaction: There is some sort of logicians' dream, going back to Leibniz, of a reasoning engine, which accepts propositions and outputs inferences. I agree with this idea. People who excel at logic are often, it seems to me, modest at philosophy. |