81 ideas
| 18835 | Logic doesn't have a metaphysical basis, but nor can logic give rise to the metaphysics [Rumfitt] |
| Full Idea: There is surely no metaphysical basis for logic, but equally there is no logical basis for metaphysics, if that implies that we can settle the choice of logic in advance of settling any seriously contested metaphysical-cum-semantic issues. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 7.5) | |
| A reaction: Is this aimed at Tim Williamson's book on treating modal logic as metaphysics? I agree with the general idea that logic won't deliver a metaphysics. I might want to defend a good metaphysics giving rise to a good logic. |
| 5728 | The concept of truth was originated by the senses [Lucretius] |
| Full Idea: The concept of truth was originated by the senses. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], IV.479) | |
| A reaction: This is a refreshing challenge to the modern view of truth, which seems entirely entangled with language. Truth seems a useful concept when discussing the workings of an animal mind. As you get closer to an object, you see it more 'truly'. |
| 18819 | The idea that there are unrecognised truths is basic to our concept of truth [Rumfitt] |
| Full Idea: The realist principle that a statement may be true even though no one is able to recognise its truth is so deeply embedded in our ordinary conception of truth that any account that flouts it is liable to engender confusion. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 5.1) |
| 18826 | 'True at a possibility' means necessarily true if what is said had obtained [Rumfitt] |
| Full Idea: A statement is 'true at a possibility' if, necessarily, things would have been as the statement (actually) says they are, had the possibility obtained. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 6.6) | |
| A reaction: This is deliberately vague about what a 'possibility' is, but it is intended to be more than a property instantiation, and less than a possible world. |
| 18803 | Semantics for propositions: 1) validity preserves truth 2) non-contradition 3) bivalence 4) truth tables [Rumfitt] |
| Full Idea: The classical semantics of natural language propositions says 1) valid arguments preserve truth, 2) no statement is both true and false, 3) each statement is either true or false, 4) the familiar truth tables. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 1.1) |
| 18814 | 'Absolute necessity' would have to rest on S5 [Rumfitt] |
| Full Idea: If there is such a notion as 'absolute necessity', its logic is surely S5. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 3.3) | |
| A reaction: There are plenty of people (mainly in the strict empiricist tradition) who don't believe in 'absolute' necessity. |
| 18798 | It is the second-order part of intuitionistic logic which actually negates some classical theorems [Rumfitt] |
| Full Idea: Although intuitionistic propositional and first-order logics are sub-systems of the corresponding classical systems, intuitionistic second-order logic affirms the negations of some classical theorems. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 1.1) |
| 18799 | Intuitionists can accept Double Negation Elimination for decidable propositions [Rumfitt] |
| Full Idea: Double Negation Elimination is a rule of inference which the classicist accepts without restriction, but which the intuitionist accepts only for decidable propositions. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 1.1) | |
| A reaction: This cures me of my simplistic understanding that intuitionists just reject the rules about double negation. |
| 18830 | Most set theorists doubt bivalence for the Continuum Hypothesis, but still use classical logic [Rumfitt] |
| Full Idea: Many set theorists doubt if the Generalised Continuum Hypothesis must be either true or false; certainly, its bivalence is far from obvious. All the same, almost all set theorists use classical logic in their proofs. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 7.2) | |
| A reaction: His point is that classical logic is usually taken to rest on bivalence. He offers the set theorists a helping hand, by defending classical logic without resorting to bivalence. |
| 18843 | The iterated conception of set requires continual increase in axiom strength [Rumfitt] |
| Full Idea: We are doomed to postulate an infinite sequence of successively stronger axiom systems as we try to spell out what is involved in iterating the power set operation 'as far as possible'. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 9.3) | |
| A reaction: [W.W. Tait is behind this idea] The problem with set theory, then, especially as a foundation of mathematics, is that it doesn't just expand, but has to keep reinventing itself. The 'large cardinal axioms' are what is referred to. |
| 18836 | A set may well not consist of its members; the empty set, for example, is a problem [Rumfitt] |
| Full Idea: There seem strong grounds for rejecting the thesis that a set consists of its members. For one thing, the empty set is a perpetual embarrassment for the thesis. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 8.4) | |
| A reaction: Rumfitt also says that if 'red' has an extension, then membership of that set must be vague. Extensional sets are precise because their objects are decided in advance, but intensional (or logical) sets, decided by a predicate, can be vague. |
| 18837 | A set can be determinate, because of its concept, and still have vague membership [Rumfitt] |
| Full Idea: Vagueness in respect of membership is consistent with determinacy of the set's identity, so long as a set's identity is taken to consist, not in its having such-and-such members, but in its being the extension of the concept A. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 8.4) | |
| A reaction: To be determinate, it must be presumed that there is some test which will decide what falls under the concept. The rule can say 'if it is vague, reject it' or 'if it is vague, accept it'. Without one of those, how could the set have a clear identity? |
| 18845 | If the totality of sets is not well-defined, there must be doubt about the Power Set Axiom [Rumfitt] |
| Full Idea: Someone who is sympathetic to the thesis that the totality of sets is not well-defined ought to concede that we have no reason to think that the Power Set Axiom is true. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 9.6) | |
| A reaction: The point is that it is only this Axiom which generates the vast and expanding totality. In principle it is hard, though, to see what is intrinsically wrong with the operation of taking the power set of a set. Hence 'limitation of size'? |
| 18815 | Logic is higher-order laws which can expand the range of any sort of deduction [Rumfitt] |
| Full Idea: On the conception of logic recommended here, logical laws are higher-order laws that can be applied to expand the range of any deductive principles. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 3.3) | |
| A reaction: You need the concept of a 'deductive principle' to get this going, but I take it that might be directly known, rather than derived from a law. |
| 18804 | The case for classical logic rests on its rules, much more than on the Principle of Bivalence [Rumfitt] |
| Full Idea: I think it is a strategic mistake to rest the case for classical logic on the Principle of Bivalence: the soundness of the classical logic rules is far more compelling than the truth of Bivalence. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 1.1) | |
| A reaction: The 'rules' to which he is referring are those of 'natural deduction', which make very few assumptions, and are intended to be intuitively appealing. |
| 18805 | Classical logic rules cannot be proved, but various lines of attack can be repelled [Rumfitt] |
| Full Idea: There is not the slightest prospect of proving that the rules of classical logic are sound. ….All that the defender of classical logic can do is scrutinize particular attacks and try to repel them. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 1.1) | |
| A reaction: This is the agenda for Rumfitt's book. |
| 18827 | If truth-tables specify the connectives, classical logic must rely on Bivalence [Rumfitt] |
| Full Idea: If we specify the senses of the connectives by way of the standard truth-tables, then we must justify classical logic only by appeal to the Principle of Bivalence. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 7) | |
| A reaction: Rumfitt proposes to avoid the truth-tables, and hence not to rely on Bivalence for his support of classical logic. He accepts that Bivalence is doubtful, citing the undecidability of the Continuum Hypothesis as a problem instance. |
| 18813 | Logical consequence is a relation that can extended into further statements [Rumfitt] |
| Full Idea: Logical consequence, I argue, is distinguished from other implication relations by the fact that logical laws may be applied in extending any implication relation so that it applies among some complex statements involving logical connectives. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 3.3) | |
| A reaction: He offers implication in electronics as an example of a non-logical implication relation. This seems to indicate that logic must be monotonic, that consequence is transitive, and that the Cut Law always applies. |
| 18808 | Normal deduction presupposes the Cut Law [Rumfitt] |
| Full Idea: Our deductive practices seem to presuppose the Cut Law. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 2.3) | |
| A reaction: That is, if you don't believe that deductions can be transitive (and thus form a successful chain of implications), then you don't really believe in deduction. It remains a well known fact that you can live without the Cut Law. |
| 18840 | When faced with vague statements, Bivalence is not a compelling principle [Rumfitt] |
| Full Idea: I do not regard Bivalence, when applied to vague statements, as an intuitively compelling principle which we ought to try to preserve. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 8.7) | |
| A reaction: The point of Rumfitt's book is to defend classical logic despite failures of bivalence. He also cites undecidable concepts such as the Continuum Hypothesis. |
| 18802 | In specifying a logical constant, use of that constant is quite unavoidable [Rumfitt] |
| Full Idea: There is no prospect whatever of giving the sense of a logical constant without using that very constant, and much else besides, in the metalinguistic principle that specifies that sense. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 1.1) |
| 18800 | Introduction rules give deduction conditions, and Elimination says what can be deduced [Rumfitt] |
| Full Idea: 'Introduction rules' state the conditions under which one may deduce a conclusion whose dominant logical operator is the connective. 'Elimination rules' state what may be deduced from some premises, where the major premise is dominated by the connective. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 1.1) | |
| A reaction: So Introduction gives conditions for deduction, and Elimination says what can actually be deduced. If my magic wand can turn you into a frog (introduction), and so I turn you into a frog, how does that 'eliminate' the wand? |
| 18809 | Logical truths are just the assumption-free by-products of logical rules [Rumfitt] |
| Full Idea: Gentzen's way of formalising logic has accustomed people to the idea that logical truths are simply the by-products of logical rules, that arise when all the assumptions on which a conclusion rests have been discharged. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 2.5) | |
| A reaction: This is the key belief of those who favour the natural deduction account of logic. If you really believe in separate logic truths, then you can use them as axioms. |
| 18807 | Monotonicity means there is a guarantee, rather than mere inductive support [Rumfitt] |
| Full Idea: Monotonicity seems to mark the difference between cases in which a guarantee obtains and those where the premises merely provide inductive support for a conclusion. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 2.3) | |
| A reaction: Hence it is plausible to claim that 'non-monotonic logic' is a contradiction in terms. |
| 18842 | Maybe an ordinal is a property of isomorphic well-ordered sets, and not itself a set [Rumfitt] |
| Full Idea: Menzel proposes that an ordinal is something isomorphic well-ordered sets have in common, so while an ordinal can be represented as a set, it is not itself a set, but a 'property' of well-ordered sets. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 9.2) | |
| A reaction: [C.Menzel 1986] This is one of many manoeuvres available if you want to distance mathematics from set theory. |
| 18834 | Infinitesimals do not stand in a determinate order relation to zero [Rumfitt] |
| Full Idea: Infinitesimals do not stand in a determinate order relation to zero: we cannot say an infinitesimal is either less than zero, identical to zero, or greater than zero. ….Infinitesimals are so close to zero as to be theoretically indiscriminable from it. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 7.4) |
| 18846 | Cantor and Dedekind aimed to give analysis a foundation in set theory (rather than geometry) [Rumfitt] |
| Full Idea: One of the motivations behind Cantor's and Dedekind's pioneering explorations in the field was the ambition to give real analysis a new foundation in set theory - and hence a foundation independent of geometry. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 9.6) | |
| A reaction: Rumfitt is inclined to think that the project has failed, although a weaker set theory than ZF might do the job (within limits). |
| 18839 | An object that is not clearly red or orange can still be red-or-orange, which sweeps up problem cases [Rumfitt] |
| Full Idea: A borderline red-orange object satisfies the disjunctive predicate 'red or orange', even though it satisfies neither 'red' or 'orange'. When applied to adjacent bands of colour, the disjunction 'sweeps up' objects which are reddish-orange. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 8.5) | |
| A reaction: Rumfitt offers a formal principle in support of this. There may be a problem with 'adjacent'. Different colour systems will place different colours adjacent to red. In other examples the idea of 'adjacent' may make no sense. Rumfitt knows this! |
| 18838 | The extension of a colour is decided by a concept's place in a network of contraries [Rumfitt] |
| Full Idea: On Sainsbury's picture, a colour has an extension that it has by virtue of its place in a network of contrary colour classifications. Something is determined to be 'red' by being a colour incompatible with orange, yellow, green, blue, indigo and violet. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 8.5) | |
| A reaction: Along with Idea 18839, this gives quite a nice account of vagueness, by requiring a foil to the vague predicate, and using the disjunction of the predicate and its foil to handle anything caught in between them. |
| 18816 | Metaphysical modalities respect the actual identities of things [Rumfitt] |
| Full Idea: The central characteristic mark of metaphysical necessity is that a metaphysical possibility respects the actual identities of things - in a capacious sense of 'thing'. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 3.4) | |
| A reaction: He contrast this with logical necessity, and concludes that some truths are metaphysically but not logically necessary, such as 'Hesperus is identical with Phosphorus'. Personally I like the idea of a 'necessity-maker', so that fits. |
| 18825 | S5 is the logic of logical necessity [Rumfitt] |
| Full Idea: I accept the widely held thesis that S5 is the logic of logical necessity. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 6.4 n16) | |
| A reaction: It seems plausible that S5 is also the logic of metaphysical necessity, but that does not make them the same thing. The two types of necessity have two different grounds. |
| 18824 | Since possibilities are properties of the world, calling 'red' the determination of a determinable seems right [Rumfitt] |
| Full Idea: Some philosophers describe the colour scarlet as a determination of the determinable red; since the ways the world might be are naturally taken to be properties of the world, it helps to bear this analogy in mind. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 6.4) | |
| A reaction: This fits nicely with the disposition accounts of modality which I favour. Hence being 'coloured' is a real property of objects, even in the absence of the name of its specific colour. |
| 18828 | If two possibilities can't share a determiner, they are incompatible [Rumfitt] |
| Full Idea: Two possibilities are incompatible when no possibility determines both. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 7.1) | |
| A reaction: This strikes me as just the right sort of language for building up a decent metaphysical picture of the world, which needs to incorporate possibilities as well as actualities. |
| 18821 | Possibilities are like possible worlds, but not fully determinate or complete [Rumfitt] |
| Full Idea: Possibilities are things of the same general character as possible worlds, on one popular conception of the latter. They differ from worlds, though, in that they are not required to be fully determinate or complete. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 6) | |
| A reaction: A rather promising approach to such things, even though a possibility is fairly determinate at its core, but very vague at the edges. It is possible that the UK parliament might be located in Birmingham, for example. Is this world 'complete'? |
| 18831 | Medieval logicians said understanding A also involved understanding not-A [Rumfitt] |
| Full Idea: Mediaeval logicians had a principle, 'Eadem est scientia oppositorum': in order to attain a clear conception of what it is for A to be the case, one needs to attain a conception of what it is for A not to be the case. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 7.2) | |
| A reaction: Presumably 'understanding' has to be a fairly comprehensive grasp of the matter, so understanding the negation sounds like a reasonable requirement for the real thing. |
| 5729 | If the senses are deceptive, reason, which rests on them, is even worse [Lucretius] |
| Full Idea: The structure of your reasoning must be rickety and defective, if the senses on which it rests are themselves deceptive. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], IV.518) | |
| A reaction: This strikes me as one of the most basic tenets of empiricism. It denies the existence of 'pure' reason, and instead asserts that it is built out of complex and abstracted sense experience, which makes it ultimately a second-class citizen. |
| 5702 | The senses are much the best way to distinguish true from false [Lucretius] |
| Full Idea: What can be a surer guide to the distinction of true from false than our own senses? | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.700) | |
| A reaction: This doesn't say they are the only guide, which leaves room for guides such as what is consistent or self-evident or inferred. There is enough here, though, to show that the Epicureans were empiricists in a fairly modern way. |
| 18820 | In English 'evidence' is a mass term, qualified by 'little' and 'more' [Rumfitt] |
| Full Idea: In English, the word 'evidence' behaves as a mass term: we speak of someone's having little evidence for an assertion, and of one thinker's having more evidence than another for a claim. One the other hand, we also speak of 'pieces' of evidence. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 5.2) | |
| A reaction: And having 'more' evidence does not mean having a larger number of pieces of evidence, so it really is like an accumulated mass. |
| 5697 | The only possible standard for settling doubts is the foundation of the senses [Lucretius] |
| Full Idea: If a belief resting directly on the foundation of the senses is not valid, there will be no standard to which we can refer any doubt on obscure questions for rational confirmation. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.422) | |
| A reaction: A classic statement of empiricist foundationalism. The Epicureans don't appear to have any time for a priori truths at all. I wonder if they settled mathematical disputes by counting objects and drawing diagrams? |
| 5727 | Most supposed delusions of the senses are really misinterpretations by the mind [Lucretius] |
| Full Idea: Paradoxical experiences (such a dreams and illusions) cannot shake our faith in the senses. Most of the illusion is due to the mental assumptions we ourselves superimpose, so that things not perceived by the senses pass for perceptions. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], IV.462) | |
| A reaction: Some misinterpretations of the senses, such as thinking a square tower round, are the result of foolish lack of judgement, but actual delusions within the senses, such as a ringing in the ears, or a pain in a amputated leg, seem like real sense failures. |
| 5714 | Even simple facts are hard to believe at first hearing [Lucretius] |
| Full Idea: No fact is so simple that it is not harder to believe than to doubt at the first presentation. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.1022) | |
| A reaction: Hence induction is just 'drumming it in' until you come to believe it. There are good evolutionary reasons why we should be like this, because we would otherwise believe all sorts of silly half-perceptions in the gloaming. |
| 5718 | The mind is in the middle of the breast, because there we experience fear and joy [Lucretius] |
| Full Idea: The guiding principle of the whole body is the mind or intellect, which is firmly lodged in the mid-region of the breast. Here is felt fear and alarm, and the caressing pulse of joy. Here, then is the seat of the intellect and mind. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.140) | |
| A reaction: Even by this date thinking people were not clear that the mind is in the brain. They paid insufficient attention to head injuries. The emotions are felt to have a location, but intellect and principles are not. |
| 5717 | The mind is a part of a man, just like a hand or an eye [Lucretius] |
| Full Idea: First, I maintain that the mind, which we often call the intellect, the seat of guidance and control of life, is part of a man, no less than hand or foot or eyes are parts of a whole living creature. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.95) | |
| A reaction: Presumably Lucretius asserts this because some people were denying it. Sounds like common sense to me. The only reason I can see for anyone denying what he says is if they are desperate to survive death. |
| 21387 | The separate elements and capacities of a mind cannot be distinguished [Lucretius] |
| Full Idea: No single element [of the soul] can be separated, nor can their capacities be divided spatially; they are like the multiple powers of a single body | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.262), quoted by A.A. Long - Hellenistic Philosophy 2.7 | |
| A reaction: It is interesting that this comes from someone with a strongly physicalist view of the mind (though not, if I recall, focusing on the brain). He is still totally impressed by the unified phenomenology of mental experience. He is an empiricist. |
| 5709 | The actions of the mind are not determinate and passive, because atoms can swerve [Lucretius] |
| Full Idea: The fact that the mind itself has no internal necessity to determine its every act and compel it to suffer in helpless passivity - this is due to the slight swerve of the atoms at no determinate time or place. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.294) | |
| A reaction: No one likes this proposal much, but it is very intriguing. The Epicureans had seen a problem, one which doesn't bother me much. If, nowadays, you are a reductive physicalist who believes in free will, you have a philosophical nightmare ahead of you. |
| 5695 | Only bodies can touch one another [Lucretius] |
| Full Idea: Nothing can touch or be touched except body. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.303) | |
| A reaction: This is the key objection to interactionism, and the main reason why the atomists have a thoroughly material view of the mind. It is an induction from a very large number of instances, but the argument is not, of course, conclusive. |
| 5711 | The earth is and always has been an insentient being [Lucretius] |
| Full Idea: The earth is and always has been an insentient being. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.658) | |
| A reaction: The fact that Epicurus needs to deny this shows that some idea close to panpsychism must still have been around in his time. He is discussing gods at the time, so maybe pantheism was the view being attacked, but that is a subset of panpsychism. |
| 5712 | Particles may have sensation, but eggs turning into chicks suggests otherwise [Lucretius] |
| Full Idea: There is the possibility that particles have senses like those of an animate being as a whole, …but from the fact that we perceive eggs turning into live fledglings, we may infer that sense can be generated from the insentient. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.914) | |
| A reaction: He gives other arguments for his view. The egg example is not a strong argument, but is precisely our puzzle of how consciousness can emerge from the process of evolution, and natural selection makes dualism look unlikely. |
| 5719 | The mind moves limbs, wakes the body up, changes facial expressions, which involve touch [Lucretius] |
| Full Idea: Mind and spirit are both composed of matter, as we see them propelling limbs, rousing the body from sleep, changing the expression of the face, and guiding the whole man - activities which clearly involves touch, which involves matter. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.164) | |
| A reaction: This is the inverse of Descartes' interaction problem, and strikes me as a straightforward common sense truth. However, if you believe in spiritual gods, this gives you a model for the interaction (however mysterious) of matter and spirit. |
| 5724 | Lions, foxes and deer have distinct characters because their minds share in their bodies [Lucretius] |
| Full Idea: Why are lions ferocious, foxes crafty, and deer timid? It can only be because the mind always shares in the specific growth of the body according to its seed and breed. If it were immortal and reincarnated, living things would have jumbled characters. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.743) | |
| A reaction: A nice argument which I have not encountered in modern times. Of course, even Descartes admits that the mind is intermingled with the body, but it seems that the essential character of a mind is dictated by the body. |
| 5713 | You needn't be made of laughing particles to laugh, so why not sensation from senseless seeds? [Lucretius] |
| Full Idea: One can laugh without being composed of laughing particles, ..so why cannot the things that we see gifted with sensation be compounded of seeds that are wholly senseless? | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.988) | |
| A reaction: Lovely argument! You might feel driven to panpsychism in your desperation to explain the 'weirdness' of consciousness, but it would be mad to attribute laughter to basic matter, so comedy has to 'emerge' at some point. |
| 18817 | We understand conditionals, but disagree over their truth-conditions [Rumfitt] |
| Full Idea: It is striking that our understanding of conditionals is not greatly impeded by widespread disagreement about their truth-conditions. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 4.2) | |
| A reaction: Compare 'if you dig there you might find gold' with 'if you dig there you will definitely find gold'. The second but not the first invites 'how do you know that?', implying truth. Two different ifs. |
| 18829 | The truth grounds for 'not A' are the possibilities incompatible with truth grounds for A [Rumfitt] |
| Full Idea: The truth-grounds of '¬A' are precisely those possibilities that are incompatible with any truth-ground of A. | |
| From: Ian Rumfitt (The Boundary Stones of Thought [2015], 7.1) | |
| A reaction: This is Rumfitt's proposal for the semantics of 'not', based on the central idea of a possibility, rather than a possible world. The incompatibility tracks back to an absence of shared grounding. |
| 6611 | One man's meat is another man's poison [Lucretius] |
| Full Idea: What is food to one may be literally poison to others. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], IV.638) | |
| A reaction: This seems to be the origin of the well-known saying. This is not relativism of perception, but a relativism of how individuals actually respond to the world. It sums up the position with, say, the operas of Wagner. |
| 5730 | Our bodies weren't created to be used; on the contrary, their creation makes a use possible [Lucretius] |
| Full Idea: Nothing in our bodies was born in order that we might be able to use it, but the thing born creates the use. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], IV.834) | |
| A reaction: This remark (strongly opposed to Aristotle's view of human function and nature) raises the obvious question of why the body is so very useful for staying alive. Most of its uses are not random. Lucretius would abandon this view if he read Darwin. |
| 5726 | The dead are no different from those who were never born [Lucretius] |
| Full Idea: One who no longer is cannot suffer, or differ in any way from one who has never been born. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.867) | |
| A reaction: There is a special kind of pain in being poor if you were once rich, which is not suffered by those who experience only poverty. Lucretius is right, but we are concerned with how we feel now, not with how we won't feel once dead. |
| 5705 | Nature only wants two things: freedom from pain, and pleasure [Lucretius] |
| Full Idea: Nature only clamours for two things, a body free from pain, a mind released from worry and fear for the enjoyment of pleasurable sensation. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.21) | |
| A reaction: I can't help agreeing with those (like Aristotle) who consider this a very demeaning view of human life. See Idea 99. Bentham agrees with Lucretius (Idea 3777). I think they are largely right, but not entirely. Other motives are possible than sensations. |
| 5716 | Nature runs the universe by herself without the aid of gods [Lucretius] |
| Full Idea: Nature is free and uncontrolled by proud masters and runs the universe by herself without the aid of gods. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.1094) | |
| A reaction: A nice remark. This apparent personification of nature implies the application of laws to an essentially passive reality. See Idea 5442 and Nature|Laws of Nature|Essentialism for a different view. |
| 5704 | There can be no centre in infinity [Lucretius] |
| Full Idea: There can be no centre in infinity. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.1069) | |
| A reaction: This is highly significant, because if we can establish that the universe is infinite (as Epicurus believes), it follows that the human race cannot be at the centre of it, as the Ptolemaic/medieval view proposed. |
| 5703 | The universe must be limitless, since there could be nothing outside to limit it [Lucretius] |
| Full Idea: The universe is not bounded in any direction. If it were, it would necessarily have a limit somewhere, but a thing cannot have a limit unless there is something outside to limit it. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.959) | |
| A reaction: This is a subtler argument than the mere enquiry about why you would have to stop at the end of the universe. It still seems a nice argument, though Einstein's curvature of space seems to have thwarted it. |
| 5693 | Everything is created and fed by nature from atoms, and they return to atoms in death [Lucretius] |
| Full Idea: The ultimate realities of heaven and the gods are the atoms, from which nature creates all things and increases and feeds them, and into which, when they perish, nature again resolves them. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.46) | |
| A reaction: Sounds right to me. Nothing in modern particle theory and string theory has refuted this claim. But what makes the atoms move, and what makes them combine in an orderly way? Is the orderliness of atoms made of atoms? Essences? |
| 5701 | If an object is infinitely subdivisible, it will be the same as the whole universe [Lucretius] |
| Full Idea: If there are no atoms, the smallest bodies will have infinite parts, since they can be endlessly halved. ..But then there will be no difference between the smallest thing and the whole universe, as they will equally have infinite parts. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.620) | |
| A reaction: Another argument which remains effective even now. There must surely (intuitively) be more divisions possible in a large object than in a small one? Unless of course there were many different sizes of infinity…. See Cantor. |
| 5708 | In downward motion, atoms occasionally swerve slightly for no reason [Lucretius] |
| Full Idea: When atoms are travelling straight down through empty space by their own weight, at quite indeterminate times and places they swerve ever so little from their course. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.217) | |
| A reaction: Never a popular theory because it seems to breach the Principle of Sufficient Reason (Ideas 306 + 3646). This seems to be the beginning of a strong need for the concept of free will, and an underlying explanation. Most thinkers put mind outside nature. |
| 17004 | Nothing can break the binding laws of eternity [Lucretius] |
| Full Idea: Nothing has power to break the binding laws of eternity. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], 5.56) | |
| A reaction: This seems to be virtually the only remark from the ancient world suggesting that there are 'laws' of nature, so I'm guessing it is a transient metaphor, not a theory about nature. 'Even the gods must bow to necessity'. |
| 5696 | If there were no space there could be no movement, or even creation [Lucretius] |
| Full Idea: We see movement everywhere, but if there were no empty space, things would be denied the power of movement - or rather, they could not possibly have come into existence, embedded as they would have been in motionless matter. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.342) | |
| A reaction: This still seems a good argument, if reality is made of particles. People can move in a crowd until it becomes too dense. |
| 5706 | Atoms move themselves [Lucretius] |
| Full Idea: Atoms move themselves. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.133) | |
| A reaction: Something has to move itself, I suppose, but then that could be psuché, giving us free will (see Idea 1424). Why does Epicurus need the 'swerve' if atoms are self-movers? See Idea 5708. |
| 5700 | It is quicker to break things up than to assemble them [Lucretius] |
| Full Idea: Anything can be more speedily disintegrated than put together again. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.558) | |
| A reaction: Clearly the concept of entropy was around long before anyone tried to give a systematic or mathematical account of it. |
| 5698 | We can only sense time by means of movement, or its absence [Lucretius] |
| Full Idea: It must not be claimed that anyone can sense time by itself apart from the movement of things or their restful immobility. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.465) | |
| A reaction: This seems a remarkably Einsteinian remark, though he is only talking of the epistemology of the matter, not the ontology. We are not far from the concept of space-time here. |
| 5715 | This earth is very unlikely to be the only one created [Lucretius] |
| Full Idea: It is in the highest degree unlikely that this earth and sky is the only one to have been created. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.1057) | |
| A reaction: I can only admire the science fiction imagination of this, which roughly agrees with the assessment of modern cosmologists. We think imagination was cramped in the ancient world, and now wanders free - but that is not so. |
| 5694 | Nothing can be created by divine power out of nothing [Lucretius] |
| Full Idea: In studying the workings of nature, our starting-point will be this principle: nothing can ever be created by divine power out of nothing. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.152) | |
| A reaction: This claim seems to cry out for a bit of empiricist caution. What observation has convinced Lucretius that creation out of nothing is impossible? The early Christians switched to the view that divine creation is 'ex nihilo' - out of nothing. |
| 5699 | If matter wasn't everlasting, everything would have disappeared by now [Lucretius] |
| Full Idea: If the matter in things had not been everlasting, everything by now would have gone back to nothing, and the things we see would be the product of rebirth out of nothing. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], I.544) | |
| A reaction: See Idea 1431, which is Aquinas's Third Way of proving God. Aquinas thinks there must be a necessary being outside of the system, but Lucretius thinks there must be some necessary existence within the system (as Hume had suggested). |
| 5707 | The universe can't have been created by gods, because it is too imperfect [Lucretius] |
| Full Idea: The universe was certainly not created for us by divine power: it is so full of imperfections. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.180) | |
| A reaction: This is certainly a problem if God is 'supremely perfect', as Descartes proposed, because then the universe would also have to be supremely perfect. See Idea 2114 for a possible answer from Leibniz. Hume agrees with Epicurus about design. |
| 5710 | Gods are tranquil and aloof, and have no need of or interest in us [Lucretius] |
| Full Idea: The nature of deity is to enjoy immortal existence in utter tranquillity, aloof and detached from our affairs. It is free from all pain and peril, strong in its own resources, exempt from any need of us, indifferent to our merits and immune from anger. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], II.652) | |
| A reaction: This seems to be the seed of late seventeenth century deism - the idea of a Creator who is now absent, and ignores our prayers. At that time 'Epicurean' became a synonym for atheist, but Epicureans never quite reached that point. |
| 5731 | Why does Jupiter never hurl lightning from a blue sky? [Lucretius] |
| Full Idea: Why does Jupiter never hurl his thunderbolt upon the earth and let loose his thunder out of a sky that is wholly blue? | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], VI.400) | |
| A reaction: Nice question! It really doesn't take very much to see through superstition, and the fact that most people believed such things shows how staggeringly uncritical they were in their thinking, until philosophers appeared and taught them how to reason. |
| 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. |
| 5720 | Spirit is mortal [Lucretius] |
| Full Idea: Spirit is mortal. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.542) | |
| A reaction: This is asserted at an historical moment when immortality is beginning to grip everyone's imagination. |
| 5722 | For a separated spirit to remain sentient it would need sense organs attached to it [Lucretius] |
| Full Idea: If spirit is immortal and can remain sentient when divorced from our body, we must credit it with possession of five senses; but eyes or nostrils or hand or tongue or ears cannot be attached to a disembodied spirit. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.624) | |
| A reaction: This is a powerful argument against immortality. If you are going to see, you must interact with photons; to hear you must respond to compression waves; to smell you must react to certain molecules. Immortality without those would be a bit dull. |
| 5725 | An immortal mind couldn't work harmoniously with a mortal body [Lucretius] |
| Full Idea: It is crazy to couple a mortal object with an eternal and suppose that they can work in harmony and mutually interact. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.799) | |
| A reaction: An interesting thought, though not a terrible persuasive argument. A god would indeed be a bit restless if it were chained to a human being, but it would presumably knuckle down to the task if firmly instructed to do it by Zeus. |
| 5721 | The mind is very small smooth particles, which evaporate at death [Lucretius] |
| Full Idea: Since the substance of the mind is extraordinarily mobile, it must consist of particles exceptionally small and smooth and round, ..so that, when the spirit has escaped from the body, the outside of the limbs appears intact and there is no loss of weight. | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.201) | |
| A reaction: Lucretius is wonderfully attentive to interesting evidence. He goes on to compare it to the evaporation of perfume. The fine-grained connections of the brain are not far off what he is proposing. |
| 5723 | If spirit is immortal and enters us at birth, why don't we remember a previous existence? [Lucretius] |
| Full Idea: If the spirit is by nature immortal and is slipped into the body at birth, why do we retain no memory of an earlier existence, no impress of antecedent events? | |
| From: Lucretius (On the Nature of the Universe [c.60 BCE], III.670) | |
| A reaction: Plato took the view that we do recall previous existence, as seen in our innate ideas. This problem forced the Christian church into the uncomfortable claim that God creates the soul at conception, but that it then goes on to immortality. |