24 ideas
| 7914 | To try to be wise all on one's own is folly [Rochefoucauld] |
| Full Idea: To try to be wise all on one's own is sheer folly. | |
| From: La Rochefoucauld (Maxims [1663], 231) | |
| A reaction: I agree strongly with this. There are counter-examples, of whom Spinoza may be the greatest, and Nietzsche thought that philosophy was essentially a solitary business, but most of us are not Spinoza or Nietzsche. |
| 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. |
| 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). |
| 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. |
| 7118 | La Rochefoucauld's idea of disguised self-love implies an unconscious mind [Rochefoucauld, by Sartre] |
| Full Idea: La Rochefoucauld is one of the first to have made use of the unconscious without naming it: for him, amour-propre conceals itself in the most diverse disguises. | |
| From: report of La Rochefoucauld (Maxims [1663]) by Jean-Paul Sartre - Transcendence of the Ego I (C) | |
| A reaction: It seems odd that no one before that ever thought that someone might have hidden motives of which even they themselves were unaware. How about Iago, or Macbeth, or Hamlet? It is a profound change in our view of human nature. |
| 7912 | Judging by effects, love looks more like hatred than friendship [Rochefoucauld] |
| Full Idea: If love be judged by its most visible effects it looks more like hatred than friendship. | |
| From: La Rochefoucauld (Maxims [1663], 072) | |
| A reaction: Presumably he is thinking of pursuit, possession and jealousy. The remark is plausible if you add the word 'sometimes' to it, but as a universal generalisation it is ridiculous, the product of a society where they competed to exceed in cynicism. |
| 7915 | Supreme cleverness is knowledge of the real value of things [Rochefoucauld] |
| Full Idea: Supreme cleverness is knowledge of the real value of things. | |
| From: La Rochefoucauld (Maxims [1663], 244) | |
| A reaction: Good. Right at the heart of wisdom is some kind of grasp of right values. It is so complex and subtle that it seems like pure intuition, but I am sure that reason is involved. 'Intelligent' people tend to be better at it. Some justifications can be given. |
| 7917 | Realising our future misery is a kind of happiness [Rochefoucauld] |
| Full Idea: To realise how much misery we have to face is in itself a kind of happiness. | |
| From: La Rochefoucauld (Maxims [1663], 570) | |
| A reaction: Probably true. Knowing that you have got hold of the truth is a sort of happiness in any area, no matter how grim the truth. However, a happy life could easily be poisoned by brooding on the future. Should the happily married brood on future solitude? |
| 7913 | Virtue doesn't go far without the support of vanity [Rochefoucauld] |
| Full Idea: Virtue would not go far without vanity to bear it company. | |
| From: La Rochefoucauld (Maxims [1663], 200) | |
| A reaction: Rochefoucauld's cynicism gets a bit tedious, but lovers of virtue must face up to this possibility when they consider what motivates them. At the heart of Aristotle there is a missing question, of what is so good about right-functioning and virtue. |
| 7916 | True friendship is even rarer than true love [Rochefoucauld] |
| Full Idea: Rare though true love may be, true friendship is rarer still. | |
| From: La Rochefoucauld (Maxims [1663], 473) | |
| A reaction: This seems to be true. Our culture doesn't encourage friendship as a high ideal. Are women better at friendship than men? Which culture, past or present, led to the greatest flourishing of friendship? Epicurus's Garden? |
| 9299 | We are bored by people to whom we ourselves are boring [Rochefoucauld] |
| Full Idea: Almost always we are bored by people to whom we ourselves are boring. | |
| From: La Rochefoucauld (Maxims [1663], 555) | |
| A reaction: An obvious exception would be a celebrity being bored with their fans. Their very excess of interest is precisely what is boring. If two people communicate well, it is unlikely that either of them will ever be bored. |
| 16713 | Philosophers are the forefathers of heretics [Tertullian] |
| Full Idea: Philosophers are the forefathers of heretics. | |
| From: Tertullian (works [c.200]), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 20.2 |
| 6610 | I believe because it is absurd [Tertullian] |
| Full Idea: I believe because it is absurd ('Credo quia absurdum est'). | |
| From: Tertullian (works [c.200]), quoted by Robert Fogelin - Walking the Tightrope of Reason n4.2 | |
| A reaction: This seems to be a rather desperate remark, in response to what must have been rather good hostile arguments. No one would abandon the support of reason if it was easy to acquire. You can't deny its engaging romantic defiance, though. |