31 ideas
| 8868 | Objective truth arises from interpersonal communication [Davidson] |
| Full Idea: The source of the concept of objective truth is interpersonal communication. | |
| From: Donald Davidson (Three Varieties of Knowledge [1991], p.209) | |
| A reaction: This is a distinctively Davidsonian idea, arising out of Wittgenstein's Private Language Argument. We could go a step further, and just say that 'objectivity is a social concept'. Davidson more or less pleads guilty to pragmatism in this essay. |
| 18951 | For scientific purposes there is a precise concept of 'true-in-L', using set theory [Putnam] |
| Full Idea: For a language L there is a predicate 'true-in-L' which one can employ for all scientific purposes in place of intuitive truth, and this predicate admits of a precise definition using only the vocabulary of L itself plus set theory. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.2) | |
| A reaction: He refers, of course, to Tarski's theory. I'm unclear of the division between 'scientific purposes' and the rest of life (which is why some people embrace 'minimal' theories of ordinary truth). I'm struck by set theory being a necessary feature. |
| 18953 | Modern notation frees us from Aristotle's restriction of only using two class-names in premises [Putnam] |
| Full Idea: In modern notation we can consider potential logical principles that Aristotle never considered because of his general practice of looking at inferences each of whose premises involved exactly two class-names. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.3) | |
| A reaction: Presumably you can build up complex inferences from a pair of terms, just as you do with pairs in set theory. |
| 18949 | The universal syllogism is now expressed as the transitivity of subclasses [Putnam] |
| Full Idea: On its modern interpretation, the validity of the inference 'All S are M; All M are P; so All S are P' just expresses the transitivity of the relation 'subclass of'. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.1) | |
| A reaction: A simple point I've never quite grasped. Since lots of syllogisms can be expressed as Venn Diagrams, in which the circles are just sets, it's kind of obvious really. So why does Sommers go back to 'terms'? See 'Term Logic'. |
| 18952 | '⊃' ('if...then') is used with the definition 'Px ⊃ Qx' is short for '¬(Px & ¬Qx)' [Putnam] |
| Full Idea: The symbol '⊃' (read 'if...then') is used with the definition 'Px ⊃ Qx' ('if Px then Qx') is short for '¬(Px & ¬Qx)'. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.3) | |
| A reaction: So ⊃ and → are just abbreviations, and not really a proper part of the language. Notoriously, though, this is quite a long way from what 'if...then' means in ordinary English, and it leads to paradoxical oddities. |
| 18958 | In type theory, 'x ∈ y' is well defined only if x and y are of the appropriate type [Putnam] |
| Full Idea: In the theory of types, 'x ∈ y' is well defined only if x and y are of the appropriate type, where individuals count as the zero type, sets of individuals as type one, sets of sets of individuals as type two. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.6) |
| 18954 | Before the late 19th century logic was trivialised by not dealing with relations [Putnam] |
| Full Idea: It was essentially the failure to develop a logic of relations that trivialised the logic studied before the end of the nineteenth century. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.3) | |
| A reaction: De Morgan, Peirce and Frege were, I believe, the people who put this right. |
| 18956 | Asserting first-order validity implicitly involves second-order reference to classes [Putnam] |
| Full Idea: The natural understanding of first-order logic is that in writing down first-order schemata we are implicitly asserting their validity, that is, making second-order assertions. ...Thus even quantification theory involves reference to classes. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.3) | |
| A reaction: If, as a nominalist, you totally rejected classes, presumably you would get by in first-order logic somehow. To say 'there are no classes so there is no logical validity' sounds bonkers. |
| 18962 | Unfashionably, I think logic has an empirical foundation [Putnam] |
| Full Idea: Today, the tendency among philosophers is to assume that in no sense does logic itself have an empirical foundation. I believe this tendency is wrong. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.9) | |
| A reaction: I agree, not on the basis of indispensability to science, but on the basis of psychological processes that lead from experience to logic. Russell and Quine are Putnam's allies here, and Frege is his opponent. Putnam developed a quantum logic. |
| 18961 | We can identify functions with certain sets - or identify sets with certain functions [Putnam] |
| Full Idea: Instead of identifying functions with certain sets, I might have identified sets with certain functions. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.9) |
| 18955 | Having a valid form doesn't ensure truth, as it may be meaningless [Putnam] |
| Full Idea: I don't think all substitution-instances of a valid schema are 'true'; some are clearly meaningless, such as 'If all boojums are snarks and all snarks are egglehumphs, then all boojums are egglehumphs'. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.3) | |
| A reaction: This seems like a very good challenge to Quine's claim that it is only form which produces a logical truth. Keep deductive and semantic consequence separate, with two different types of 'logical truth'. |
| 18959 | Sets larger than the continuum should be studied in an 'if-then' spirit [Putnam] |
| Full Idea: Sets of a very high type or very high cardinality (higher than the continuum, for example) should today be investigated in an 'if-then' spirit. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.7) | |
| A reaction: This attitude goes back to Hilbert, but it fits with Quine's view of what is indispensable for science. It is hard to see a reason for the cut-off, just looking at the logic of expanding sets. |
| 22180 | Multiple realisability is said to make reduction impossible [Okasha] |
| Full Idea: Philosophers have often invoked multiple realisability to explain why psychology cannot be reduced to physics or chemistry, but in principle the explanation works for any higher-level science. | |
| From: Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 3) | |
| A reaction: He gives the example of a 'cell' in biology, which can be implemented in all sorts of ways. Presumably that can be reduced to many sorts of physics, but not just to one sort. The high level contains patterns that vanish at the low level. |
| 18957 | Nominalism only makes sense if it is materialist [Putnam] |
| Full Idea: Nominalists must at heart be materialists, or so it seems to me: otherwise their scruples are unintelligible. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.5) | |
| A reaction: This is modern nominalism - the rejection of abstract objects. I largely plead guilty to both charges. |
| 18950 | Physics is full of non-physical entities, such as space-vectors [Putnam] |
| Full Idea: Physics is full of references to such 'non-physical' entities as state-vectors, Hamiltonians, Hilbert space etc. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.2) | |
| A reaction: I take these to be concepts which are 'abstracted' from the physical facts, and so they don't strike me as being much of an ontological problem, or an objection to nominalism (which Putnam takes them to be). |
| 8867 | A belief requires understanding the distinctions of true-and-false, and appearance-and-reality [Davidson] |
| Full Idea: Having a belief demands in addition appreciating the contrast between true belief and false, between appearance and reality, mere seeming and being. | |
| From: Donald Davidson (Three Varieties of Knowledge [1991], p.209) | |
| A reaction: This sets the bar very high for belief (never mind knowledge), and seems to imply that animals don't have beliefs. How should we describe their cognitive states then? I would say these criteria only apply to actual knowledge. |
| 10347 | Objectivity is intersubjectivity [Davidson] |
| Full Idea: An entity is objective in so far as it is intersubjective. | |
| From: Donald Davidson (Three Varieties of Knowledge [1991]), quoted by Martin Kusch - Knowledge by Agreement Ch.10 | |
| A reaction: This thought baffled me until I saw it in the context of socialised epistemology. Effectively objectivity is subsumed under justification, which in turn is seen in a social context, not private to individuals. |
| 22172 | Not all sciences are experimental; astronomy relies on careful observation [Okasha] |
| Full Idea: Not all sciences are experimental - astronomers obviously cannot do experiments on the heavens, but have to content themselves with careful observation instead. | |
| From: Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 1) | |
| A reaction: Biology too. Psychology tries hard to be experimental, but I doubt whether the main theories emerge from experiments. |
| 22177 | Randomised Control Trials have a treatment and a control group, chosen at random [Okasha] |
| Full Idea: In the Randomised Controlled Trial for a new drug, patients are divided at random into a treatment group who receive the drug, and a control group who do not. Randomisation is important to eliminate confounding factors. | |
| From: Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 2) | |
| A reaction: [compressed] Devised in the 1930s, and a major breakthrough in methodology for that kind of trial. Psychologists use the method all the time. Some theorists say it is the only reliable method. |
| 18960 | Most predictions are uninteresting, and are only sought in order to confirm a theory [Putnam] |
| Full Idea: Scientists want successful predictions in order to confirm their theories; they do not want theories in order to obtain the predictions, which are in some cases of not the slightest interest in themselves. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.8) | |
| A reaction: Equally, we might only care about the prediction, and have no interest at all in the theory. Farmers want weather predictions, not a PhD in meteorology. |
| 22174 | The discoverers of Neptune didn't change their theory because of an anomaly [Okasha] |
| Full Idea: Adams and Leverrier began with Newton's theory of gravity, which made an incorrect prediction about the orbit of Uranus. They explained away the conflicting observations by postulating a new planet, Neptune. | |
| From: Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 1) | |
| A reaction: The falsificationists can say that the anomalous observation did not falsify the theory, because they didn't know quite what they were observing. It was not in fact an anomaly for Newtonian theory at all. |
| 22175 | Science mostly aims at confirming theories, rather than falsifying them [Okasha] |
| Full Idea: The goal of science is not solely to refute theories, but also to determine which theories are true (or probably true). When a scientist collects data …they are trying to show that their own theory is true. | |
| From: Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 2) | |
| A reaction: This is the aim of 'accommodation' to a wide set of data, rather than prediction or refutation. |
| 22182 | Theories with unobservables are underdetermined by the evidence [Okasha] |
| Full Idea: According to anti-realists, scientific theories which posit unobservable entities are underdetermined by the empirical data - there will always be a number of competing theories which can account for the data equally well. | |
| From: Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 4) | |
| A reaction: The fancy version is Putnam's model theoretic argument, explored by Tim Button. The reply, apparently, is that there are other criteria for theory choice, apart from the data. And we don't have to actually observe everything in a theory. |
| 22185 | Two things can't be incompatible if they are incommensurable [Okasha] |
| Full Idea: If two things are incommensurable they cannot be incompatible. | |
| From: Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 5) | |
| A reaction: Kuhn had claimed that two rival theories are incompatible, which forces the paradigm shift. He can't stop the slide off into total relativism. The point is there cannot be a conflict if there cannot even be a comparison. |
| 22176 | Induction is inferences from examined to unexamined instances of a given kind [Okasha] |
| Full Idea: Some philosophers use 'inductive' to just mean not deductive, …but we reserve it for inferences from examined to unexamined instances of a given kind. | |
| From: Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 2) | |
| A reaction: The instances must at least be comparable. Must you know the kind before you start? Surely you can examine a sequence of things, trying to decide whether or not they are of one kind? Is checking the uniformity of a kind induction? |
| 22178 | If the rules only concern changes of belief, and not the starting point, absurd views can look ratiional [Okasha] |
| Full Idea: If the only objective constraints concern how we should change our credences, but what our initial credences should be is entirely subjective, then individuals with very bizarre opinions about the world will count as perfectly rational. | |
| From: Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 2) | |
| A reaction: The important rationality has to be the assessement of a diverse batch of evidence, for which there can never be any rules or mathematics. |
| 8866 | If we know other minds through behaviour, but not our own, we should assume they aren't like me [Davidson] |
| Full Idea: If the mental states of others are known only through their behavioral and other outward manifestations, while this is not true of our own mental states, why should we think our own mental states are anything like those of others? | |
| From: Donald Davidson (Three Varieties of Knowledge [1991], p.207) | |
| A reaction: His point is that if you seriously doubt other minds, you should follow through on the implications. But that is to treat it as a theory about other minds, rather an a sceptical worry. Descartes didn't walk into walls while writing Meditation 1. |
| 10346 | Knowing other minds rests on knowing both one's own mind and the external world [Davidson, by Dummett] |
| Full Idea: Davidson argues that knowledge of other minds presupposes knowledge of one's own mind, and that there is no knowledge of other minds without knowledge of the external world. | |
| From: report of Donald Davidson (Three Varieties of Knowledge [1991]) by Michael Dummett - Common Sense and Physics Ch.10 | |
| A reaction: Davidson't argument is actually hard to swallow because it is so long and complex. Compressing the point makes it begin to sound like a variant of the argument from analogy. |
| 8870 | Content of thought is established through communication, so knowledge needs other minds [Davidson] |
| Full Idea: Until a baseline has been established by communication with someone else, there is no point is saying one's own thoughts have a propositional content. Hence knowledge of another mind is essential all thought and all knowledge. | |
| From: Donald Davidson (Three Varieties of Knowledge [1991], p.213) | |
| A reaction: This really is building a skyscraper on the slightly shaky claims of the Private Language Argument (e.g. Idea 4158). Animals are so important in discussions of this kind. Is an albatross more or less devoid of thought and belief? |
| 8869 | The principle of charity attributes largely consistent logic and largely true beliefs to speakers [Davidson] |
| Full Idea: Concerning charity, the Principle of Coherence seeks logical consistency in the thought of the speaker, and the Principle of Correspondence seeks a similar response to features of the world to that of an interpreter. The speaker has logic and true belief. | |
| From: Donald Davidson (Three Varieties of Knowledge [1991], p.211) | |
| A reaction: Davidson adds a Kantian commitment to pure and universal reason to the very sceptical framework created by Quine. I agree with Davidson, but it seems more like faith than like an argument or an empirical observation. |
| 22173 | Galileo refuted the Aristotelian theory that heavier objects fall faster [Okasha] |
| Full Idea: Galileo's most enduring contribution lay in mechanics, where he refuted the Aristotelian theory that heavier bodies fall faster than lighter. | |
| From: Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 2) | |
| A reaction: This must the first idea in the theory of mechanics, allowing mathematical treatment and accurate comparisons. |