26 ideas
| 13838 | A decent modern definition should always imply a semantics [Hacking] |
| Full Idea: Today we expect that anything worth calling a definition should imply a semantics. | |
| From: Ian Hacking (What is Logic? [1979], §10) | |
| A reaction: He compares this with Gentzen 1935, who was attempting purely syntactic definitions of the logical connectives. |
| 13833 | 'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking] |
| Full Idea: 'Dilution' (or 'Thinning') provides an essential contrast between deductive and inductive reasoning; for the introduction of new premises may spoil an inductive inference. | |
| From: Ian Hacking (What is Logic? [1979], §06.2) | |
| A reaction: That is, inductive logic (if there is such a thing) is clearly non-monotonic, whereas classical inductive logic is monotonic. |
| 13834 | Gentzen's Cut Rule (or transitivity of deduction) is 'If A |- B and B |- C, then A |- C' [Hacking] |
| Full Idea: If A |- B and B |- C, then A |- C. This generalises to: If Γ|-A,Θ and Γ,A |- Θ, then Γ |- Θ. Gentzen called this 'cut'. It is the transitivity of a deduction. | |
| From: Ian Hacking (What is Logic? [1979], §06.3) | |
| A reaction: I read the generalisation as 'If A can be either a premise or a conclusion, you can bypass it'. The first version is just transitivity (which by-passes the middle step). |
| 13835 | Only Cut reduces complexity, so logic is constructive without it, and it can be dispensed with [Hacking] |
| Full Idea: Only the cut rule can have a conclusion that is less complex than its premises. Hence when cut is not used, a derivation is quite literally constructive, building up from components. Any theorem obtained by cut can be obtained without it. | |
| From: Ian Hacking (What is Logic? [1979], §08) |
| 13845 | The various logics are abstractions made from terms like 'if...then' in English [Hacking] |
| Full Idea: I don't believe English is by nature classical or intuitionistic etc. These are abstractions made by logicians. Logicians attend to numerous different objects that might be served by 'If...then', like material conditional, strict or relevant implication. | |
| From: Ian Hacking (What is Logic? [1979], §15) | |
| A reaction: The idea that they are 'abstractions' is close to my heart. Abstractions from what? Surely 'if...then' has a standard character when employed in normal conversation? |
| 13840 | First-order logic is the strongest complete compact theory with Löwenheim-Skolem [Hacking] |
| Full Idea: First-order logic is the strongest complete compact theory with a Löwenheim-Skolem theorem. | |
| From: Ian Hacking (What is Logic? [1979], §13) |
| 13844 | A limitation of first-order logic is that it cannot handle branching quantifiers [Hacking] |
| Full Idea: Henkin proved that there is no first-order treatment of branching quantifiers, which do not seem to involve any idea that is fundamentally different from ordinary quantification. | |
| From: Ian Hacking (What is Logic? [1979], §13) | |
| A reaction: See Hacking for an example of branching quantifiers. Hacking is impressed by this as a real limitation of the first-order logic which he generally favours. |
| 13842 | Second-order completeness seems to need intensional entities and possible worlds [Hacking] |
| Full Idea: Second-order logic has no chance of a completeness theorem unless one ventures into intensional entities and possible worlds. | |
| From: Ian Hacking (What is Logic? [1979], §13) |
| 13837 | With a pure notion of truth and consequence, the meanings of connectives are fixed syntactically [Hacking] |
| Full Idea: My doctrine is that the peculiarity of the logical constants resides precisely in that given a certain pure notion of truth and consequence, all the desirable semantic properties of the constants are determined by their syntactic properties. | |
| From: Ian Hacking (What is Logic? [1979], §09) | |
| A reaction: He opposes this to Peacocke 1976, who claims that the logical connectives are essentially semantic in character, concerned with the preservation of truth. |
| 13839 | Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers [Hacking] |
| Full Idea: For some purposes the variables of first-order logic can be regarded as prepositions and place-holders that could in principle be dispensed with, say by a system of arrows indicating what places fall in the scope of which quantifier. | |
| From: Ian Hacking (What is Logic? [1979], §11) | |
| A reaction: I tend to think of variables as either pronouns, or as definite descriptions, or as temporary names, but not as prepositions. Must address this new idea... |
| 13843 | If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking] |
| Full Idea: A Löwenheim-Skolem theorem holds for anything which, on my delineation, is a logic. | |
| From: Ian Hacking (What is Logic? [1979], §13) | |
| A reaction: I take this to be an unusually conservative view. Shapiro is the chap who can give you an alternative view of these things, or Boolos. |
| 12716 | The concept of forces or powers best reveals the true concept of substance [Leibniz] |
| Full Idea: The concept of forces or powers ..for whose explanation I have set up a distinct science of dynamics, brings the strongest light to bear upon our understanding of the true concept of substance. | |
| From: Gottfried Leibniz (De primae philosophiae emendatione [1694], G IV 469), quoted by Daniel Garber - Leibniz:Body,Substance,Monad 4 | |
| A reaction: My own experience was that as soon as I encountered the notion of a 'power' in the metaphysics of science (see Molnar on this) the whole thing began to form a coherent picture. Powers rule. |
| 6685 | 'Subjectivism' is an extension of relativism from the social group to the individual [Graham] |
| Full Idea: What is called 'subjectivism' is really just an extension of relativism from the level of the social group to the level of the individual. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.1) | |
| A reaction: Personally I prefer to stick with 'relativism', at any level. 'Relative' is a two-place predicate, so we should always specify what is relative to what, unless it is obvious from context. Morality might be relative to God, for example. |
| 6699 | The chain of consequences may not be the same as the chain of responsibility [Graham] |
| Full Idea: From a utilitarian point of view, the error of Archduke Ferdinand's driver (he turned up a cul-de-sac) was the worst in history, ...but the chain of consequences may not be the same as the chain of responsibility. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.7) | |
| A reaction: Can you cause something, and yet not be responsible for it? The driver was presumably fully conscious, rational and deliberate. He must share the responsibility for catastrophe, just as he shares in the causing of all the consequences. |
| 6698 | Negative consequences are very hard (and possibly impossible) to assess [Graham] |
| Full Idea: Negative consequences make the extension of the consequences of our actions indefinite, and this means that it is difficult to assess them; it may make it impossible, since there is now no clear sense to the idea of THE consequences of an action at all. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.7) | |
| A reaction: The general slogan of 'Do your best' covers most objections to the calculation of consequences. It is no excuse for stealing a wallet that 'at least I wasn't committing genocide'. How easy were the alternative actions to do? |
| 6700 | We can't criticise people because of unforeseeable consequences [Graham] |
| Full Idea: It is unreasonable to say that people have acted badly because of consequences which were not merely unforeseen but unforeseeable. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.7) | |
| A reaction: Interesting, and it sounds right. A key question in moral philosophy is how much effort people should make to assess the consequences of their actions. We must surely absolve them of the truly 'unforeseeable' consequence. |
| 6704 | Egoism submits to desires, but cannot help form them [Graham] |
| Full Idea: Egoism is inadequate as a guide to good living. Though it tells us what to do, given pre-existent desires, it cannot help us critically form those desires. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.9) | |
| A reaction: A crucial point in morality. It also applies to utilitarianism (should I change my capacity for pleasure?), and virtue theory (how should I genetically engineer 'human nature'?). I think these problems push us towards Platonism. See Idea 4840. |
| 6701 | Rescue operations need spontaneous benevolence, not careful thought [Graham] |
| Full Idea: If more lives are to be saved in natural disasters, what is needed is spontaneity on the part of the rescuers, a willingness not to stop and think but to act spontaneously. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.7) | |
| A reaction: This seems right, but must obviously be applied with caution, as when people are drowned attempting hopeless rescues. The most valuable person in an earthquake may be the thinker, not the digger. |
| 6693 | 'What if everybody did that?' rather misses the point as an objection to cheating [Graham] |
| Full Idea: I can object to your walking on the grass by asking 'What if everybody did that?', but the advantages of cheating depend upon the fact that most people don't cheat, so justifying my own cheating must involve special pleading. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.6) | |
| A reaction: It is, of course, reasonable to ask 'What if everybody cheated?', but it is also reasonable to reply that 'the whole point of cheating is that it exploits the honesty of others'. This shows that Kant cannot simply demolish the 'free rider'. |
| 6691 | It is more plausible to say people can choose between values, than that they can create them [Graham] |
| Full Idea: To say that individuals are free to choose their own values is more naturally interpreted as meaning that they are free to choose between pre-existent values. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.5) | |
| A reaction: Existentialism seems absurdly individualistic in its morality. Nietzsche was the best existentialist, who saw that most people have to be sheep. Strong personalities can promote or demote the old values on the great scale of what is good. |
| 6688 | Life is only absurd if you expected an explanation and none turns up [Graham] |
| Full Idea: If 'life is absurd' just means 'there is no logical explanation for human existence', we have no reason for anguish, unless we think there should be such an explanation. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.5) | |
| A reaction: This is aimed at Kierkegaard and Camus. 'Absurd' certainly seems to be a relative notion, and we have nothing to compare life with. However, life does strike us as a bit odd sometimes, don't you think? |
| 6705 | Existentialism may transcend our nature, unlike eudaimonism [Graham] |
| Full Idea: It is the freedom to transcend our nature which eudaimonism seems to ignore and existentialism brings to the fore. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.9) | |
| A reaction: It is wildly exciting to 'transcend our nature', and very dreary to polish up the nature which is given to us. In this I am a bit conservative. We should not go against the grain, but we shouldn't assume current living is the correct line of the grain. |
| 6690 | A standard problem for existentialism is the 'sincere Nazi' [Graham] |
| Full Idea: A standard problem for existentialism is the 'sincere Nazi'; there were undoubtedly some true believers, who saw in Nazism a creed that they wanted to believe, and who freely chose to endorse it. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.5) | |
| A reaction: The failing of Nazis was that they were not good citizens. They might have been good members of a faction, but they were (in my opinion) poor citizens of Germany, and (obviously) appalling citizens of Europe. The objection to existentialism is good. |
| 6689 | The key to existentialism: the way you make choices is more important than what you choose [Graham] |
| Full Idea: The chief implication of existentialism is this: what you choose to do, how you choose to spend your life, is not as important as the way you choose it. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.5) | |
| A reaction: While existentialists place emphasis on some notion of 'pure' choice, this is very close to the virtue theory idea that in a dilemma there may be several different choices which could all be rightly made by virtuous people. Integrity is a central virtue. |
| 6706 | The great religions are much more concerned with the religious life than with ethics [Graham] |
| Full Idea: The fact is that the great religions of the world are not principally concerned with ethics at all, but with the religious life for its own sake. ..The Sermon on the Mount, for example, is mainly concerned with how to pray and worship. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.9) | |
| A reaction: This seems to me a highly significant point, given that most people nowadays seem to endorse religion precisely because they wish to endorse morality, and think religion is its essential underpinning. See Idea 336 for the core problem ('Euthyphro'). |
| 6709 | Western religion saves us from death; Eastern religion saves us from immortality [Graham] |
| Full Idea: For Western minds, religion entails the belief and hope that we will be saved from death and live forever, but the belief of Eastern religions is that we do live forever, and it is from this dreadful fate that we must look to spirituality to save us. | |
| From: Gordon Graham (Eight Theories of Ethics [2004], Ch.9) | |
| A reaction: Nice. I have certainly come to prefer the Eastern view, simply on the grounds that human beings have a limited capacity. I quite fancy three hundred years of healthy life, but after that I am sure that any potential I have will be used up. |