43 ideas
| 7791 | The simplest of the logics based on possible worlds is Lewis's S5 [Lewis,CI, by Girle] |
| Full Idea: C.I.Lewis constructed five axiomatic systems of modal logic, and named them S1 to S5. It turns out that the simplest of the logics based on possible worlds is the same as Lewis's S5. | |
| From: report of C.I. Lewis (works [1935]) by Rod Girle - Modal Logics and Philosophy 2.1 | |
| A reaction: Nathan Salmon ('Reference and Essence' 2nd ed) claims (on p.xvii) that "the correct modal logic is weaker than S5 and weaker even than S4". Which is the greater virtue, simplicity or weakness? |
| 9358 | There are several logics, none of which will ever derive falsehoods from truth [Lewis,CI] |
| Full Idea: The fact is that there are several logics, markedly different, each self-consistent in its own terms and such that whoever, using it, avoids false premises, will never reach a false conclusion. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.366) | |
| A reaction: As the man who invented modal logic in five different versions, he speaks with some authority. Logicians now debate which version is the best, so how could that be decided? You could avoid false conclusions by never reasoning at all. |
| 9357 | Excluded middle is just our preference for a simplified dichotomy in experience [Lewis,CI] |
| Full Idea: The law of excluded middle formulates our decision that whatever is not designated by a certain term shall be designated by its negative. It declares our purpose to make a complete dichotomy of experience, ..which is only our penchant for simplicity. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.365) | |
| A reaction: I find this view quite appealing. 'Look, it's either F or it isn't!' is a dogmatic attitude which irritates a lot of people, and appears to be dispensible. Intuitionists in mathematics dispense with the principle, and vagueness threatens it. |
| 9364 | Names represent a uniformity in experience, or they name nothing [Lewis,CI] |
| Full Idea: A name must represent some uniformity in experience or it names nothing. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.368) | |
| A reaction: I like this because, in the quintessentially linguistic debate about the exact logical role of names, it reminds us that names arise because of the way reality is; they are not sui generis private games for logicians. |
| 11002 | Equating necessity with informal provability is the S4 conception of necessity [Lewis,CI, by Read] |
| Full Idea: C.I.Lewis's S4 system develops a sense of necessity as 'provability' in some fairly informal sense. | |
| From: report of C.I. Lewis (works [1935]) by Stephen Read - Thinking About Logic Ch. 4 |
| 9240 | Love creates a necessity concerning what to care about [Frankfurt] |
| Full Idea: The necessity with which love binds the will puts an end to indecisiveness concerning what to care about. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 2.13) | |
| A reaction: I put this here as a reminder that there may be more to necessity than the dry concept of metaphysicians and logicians. 'Why did you rescue that man first?' 'Because I love him'. Kit Fine recognises many sorts of necessity. |
| 9362 | Necessary truths are those we will maintain no matter what [Lewis,CI] |
| Full Idea: Those laws and those laws only have necessary truth which we are prepared to maintain, no matter what. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.367) | |
| A reaction: This bold and simple claim has famously been torpedoed by a well-known counterexample - that virtually every human being will cling on to the proposition "dogs have at some time existed" no matter what, but it clearly isn't a necessary truth. |
| 7803 | Modal logic began with translation difficulties for 'If...then' [Lewis,CI, by Girle] |
| Full Idea: C.I.Lewis began his groundbreaking work in modal logic because he was concerned about the unreliability of the material conditional as a translation of 'If ... then' conditionals. | |
| From: report of C.I. Lewis (Symbolic Logic (with Langford) [1932]) by Rod Girle - Modal Logics and Philosophy 12.3 | |
| A reaction: Compare 'if this is square then it has four corners' with 'if it rains then our afternoon is ruined'. Different modalities seem to be involved. We even find that 'a square has four corners' will be materially implied if it rains! |
| 19743 | A notebook counts as memory, if is available to consciousness and guides our actions [Clark/Chalmers] |
| Full Idea: Beliefs are partly constituted by features of the environment. ....a notebook plays for one person the same role that memory plays for another. ...The information is reliably there, available to consciousness, and to guide action, just as belief is. | |
| From: A Clark / D Chalmers (The Extended Mind [1998], §4) | |
| A reaction: This is the modern externalist approach to beliefs (along with broad content and external cognition systems). Not quite what we used to mean by beliefs, but we'll get used to it. I believe Plato wrote what it said in his books. Is memory just a role? |
| 9365 | We can maintain a priori principles come what may, but we can also change them [Lewis,CI] |
| Full Idea: The a priori contains principles which can be maintained in the face of all experience, representing the initiative of the mind. But they are subject to alteration on pragmatic grounds, if expanding experience shows their intellectual infelicity. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.373) | |
| A reaction: [compressed] This simply IS Quine's famous 'web of belief' picture, showing how firmly Quine is in the pragmatist tradition. Lewis treats a priori principles as a pragmatic toolkit, which can be refined to be more effective. Not implausible... |
| 21500 | We rely on memory for empirical beliefs because they mutually support one another [Lewis,CI] |
| Full Idea: When the whole range of empirical beliefs is taken into account, all of them more or less dependent on memorial knowledge, we find that those which are most credible can be assured by their mutual support, or 'congruence'. | |
| From: C.I. Lewis (An Analysis of Knowledge and Valuation [1946], 334), quoted by Erik J. Olsson - Against Coherence 3.1 | |
| A reaction: Lewis may be over-confident about this, and is duly attacked by Olson, but it seems to me roughly correct. How do you assess whether some unusual element in your memory was a dream or a real experience? |
| 21501 | If we doubt memories we cannot assess our doubt, or what is being doubted [Lewis,CI] |
| Full Idea: To doubt our sense of past experience as founded in actuality, would be to lose any criterion by which either the doubt itself or what is doubted could be corroborated. | |
| From: C.I. Lewis (An Analysis of Knowledge and Valuation [1946], 358), quoted by Erik J. Olsson - Against Coherence 3.3.1 | |
| A reaction: Obviously scepticism about memory can come in degrees, but total rejection of short-term and clear memories looks like a non-starter. What could you put in its place? Hyper-rationalism? Even maths needs memory. |
| 6556 | If anything is to be probable, then something must be certain [Lewis,CI] |
| Full Idea: If anything is to be probable, then something must be certain. | |
| From: C.I. Lewis (An Analysis of Knowledge and Valuation [1946], 186), quoted by Robert Fogelin - Walking the Tightrope of Reason Intro | |
| A reaction: Lewis makes this comment when facing infinite regress problems. It is a very nice slogan for foundationalism, which embodies the slippery slope view. Personally I feel the emotional pull of foundations, but acknowledge the very strong doubts about them. |
| 21498 | Congruents assertions increase the probability of each individual assertion in the set [Lewis,CI] |
| Full Idea: A set of statements, or a set of supposed facts asserted, will be said to be congruent if and only if they are so related that the antecedent probability of any one of them will be increased if the remainder of the set can be assumed as given premises. | |
| From: C.I. Lewis (An Analysis of Knowledge and Valuation [1946], 338), quoted by Erik J. Olsson - Against Coherence 2.2 | |
| A reaction: This thesis is vigorously attacked by Erik Olson, who works through the probability calculations. There seems an obvious problem without that. How else do you assess 'congruence', other than by evidence of mutual strengthening? |
| 6176 | A mechanism can count as 'cognitive' whether it is in the brain or outside it [Clark/Chalmers, by Rowlands] |
| Full Idea: If the operation of a brain implant inside the brain is a cognitive operation, why should it not count as a cognitive operation when it is outside the brain? There are many mechanisms which would count as cognitive if they were inside the subject. | |
| From: report of A Clark / D Chalmers (The Extended Mind [1998]) by Mark Rowlands - Externalism Ch.9 | |
| A reaction: This argues for externalism of the vehicle of thought, rather than its content. The idea is that there is no significant difference between remembering a phone number and writing it on a bit of paper. I find it hard to disagree. |
| 19741 | If something in the world could equally have been a mental process, it is part of our cognition [Clark/Chalmers] |
| Full Idea: If, as we confront some task, a part of the world functions as a process which, were it done in the head, we would have no hesitation in recognising as part of the cognitive process, then that part of the world is part of the cognitive process. | |
| From: A Clark / D Chalmers (The Extended Mind [1998], §2) | |
| A reaction: In some sense they are obviously right that our cognitive activities spill out into books, calculators, record-keeping. It seems more like an invitation to shift the meaning of the word 'mind', than a proof that we have got it wrong. |
| 19742 | Consciousness may not extend beyond the head, but cognition need not be conscious [Clark/Chalmers] |
| Full Idea: Many identify the cognitive with the conscious, and it seems far from plausible that consciousness extends outside the head in these cases. But not every cognitive process, at least on standard usage, is a conscious process. | |
| From: A Clark / D Chalmers (The Extended Mind [1998], §3) | |
| A reaction: This gives you two sorts of externalism about mind to consider. No, three, if you say there is extended conceptual content, then extended cognition processes, then extended consciousness. Depends what you mean by 'consciousness'. |
| 9264 | Persons are distinguished by a capacity for second-order desires [Frankfurt] |
| Full Idea: The essential difference between persons and other creatures is in the structure of the will, with their peculiar characteristic of being able to form 'second-order desires'. | |
| From: Harry G. Frankfurt (Freedom of the Will and concept of a person [1971], Intro) | |
| A reaction: There are problems with this - notably that all strategies of this kind just shift the problem up to the next order, without solving it - but this still strikes me as a very promising line of thinking when trying to understand ourselves. See Idea 9266. |
| 9266 | A person essentially has second-order volitions, and not just second-order desires [Frankfurt] |
| Full Idea: It is having second-order volitions, and not having second-order desires generally, that I regard as essential to being a person. | |
| From: Harry G. Frankfurt (Freedom of the Will and concept of a person [1971], §II) | |
| A reaction: Watson criticises Frankfurt for just pushing the problem up to the the next level, but Frankfurt is not offering to explain the will. He merely notes that this structure produces the sort of behaviour which is characteristic of persons, and he is right. |
| 19744 | If a person relies on their notes, those notes are parted of the extended system which is the person [Clark/Chalmers] |
| Full Idea: If Otto relies on his notebook, what this comes to is that Otto himself is best regarded as an extended system, a coupling of biological organism and external resources. | |
| From: A Clark / D Chalmers (The Extended Mind [1998], §5) | |
| A reaction: You start to get giddy as you read this stuff. If two people constantly share a notebook, they begin to blend into one another. It inclines me towards a more 'animalist' view of the nature of a person or a self. |
| 9267 | Free will is the capacity to choose what sort of will you have [Frankfurt] |
| Full Idea: The statement that a person enjoys freedom of the will means that he is free to want what he wants to want. More precisely, he is free to will what he wants to will, or to have the will he wants. | |
| From: Harry G. Frankfurt (Freedom of the Will and concept of a person [1971], §III) | |
| A reaction: A good proposal. It covers kleptomaniacs and drug addicts quite well. Thieves have second-order desires (to steal) of which kleptomaniacs are incapable. There is actually no such thing as free will, but this sort of thing will do. |
| 5828 | Extension is the class of things, intension is the correct definition of the thing, and intension determines extension [Lewis,CI] |
| Full Idea: "The denotation or extension of a term is the class of all actual or existent things which the term correctly applies to or names; the connotation or intension of a term is delimited by any correct definition of it." ..And intension determines extension. | |
| From: C.I. Lewis (An Analysis of Knowledge and Valuation [1946]), quoted by Stephen P. Schwartz - Intro to Naming,Necessity and Natural Kinds §II | |
| A reaction: The last part is one of the big ideas in philosophy of language, which was rejected by Putnam and co. If you were to reverse the slogan, though, (to extension determines intension) how would you identify the members of the extension? |
| 9361 | We have to separate the mathematical from physical phenomena by abstraction [Lewis,CI] |
| Full Idea: Physical processes present us with phenomena in which the purely mathematical has to be separated out by abstraction. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.367) | |
| A reaction: This is the father of modal logic endorsing traditional abstractionism, it seems. He is also, though, endorsing the view that a priori knowledge is created by us, with pragmatic ends in view. |
| 9265 | The will is the effective desire which actually leads to an action [Frankfurt] |
| Full Idea: A person's will is the effective desire which moves (or will or would move) a person all the way to action. The will is not coextensive with what an agent intends to do, since he may do something else instead. | |
| From: Harry G. Frankfurt (Freedom of the Will and concept of a person [1971], §I) | |
| A reaction: Essentially Hobbes's view, but with an arbitrary distinction added. If the desire is only definitely a 'will' if it really does lead to action, then it only becomes the will after the action starts. The error is thinking that will is all-or-nothing. |
| 20015 | Freedom of action needs the agent to identify with their reason for acting [Frankfurt, by Wilson/Schpall] |
| Full Idea: Frankfurt says that basic issues concerning freedom of action presuppose and give weight to a concept of 'acting on a desire with which the agent identifies'. | |
| From: report of Harry G. Frankfurt (Freedom of the Will and concept of a person [1971]) by Wilson,G/Schpall,S - Action 1 | |
| A reaction: [the cite Frankfurt 1988 and 1999] I'm not sure how that works when performing a grim duty, but it sounds quite plausible. |
| 9228 | Ranking order of desires reveals nothing, because none of them may be considered important [Frankfurt] |
| Full Idea: Ranking desires in order of preference is no help, because a person who wants one thing more than another may not regard the former as any more important to him than the latter. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 1.5) | |
| A reaction: A salutary warning. Someone may pursue something with incredible intensity, but only to stave off a boring and empty existence. The only way I can think of to assess what really matters to people is - to ask them! |
| 9270 | A 'wanton' is not a person, because they lack second-order volitions [Frankfurt] |
| Full Idea: I use the term 'wanton' to refer to agents who have first-order desires but who are not persons because, whether or not they have desires of the second-order, they have no second-order volitions. | |
| From: Harry G. Frankfurt (Freedom of the Will and concept of a person [1971], §II) | |
| A reaction: He seems to be describing someone who behaves like an animal, performing actions without ever stopping to think about them. Presumably some persons occasionally become wantons, if, for example, they have an anger problem. |
| 9269 | A person may be morally responsible without free will [Frankfurt] |
| Full Idea: It is not true that a person is morally responsible for what he has done only if his will was free when he did it. He may be morally responsible for having done it even though his will was not free at all. | |
| From: Harry G. Frankfurt (Freedom of the Will and concept of a person [1971], §IV) | |
| A reaction: Frankfurt seems to be one of the first to assert this break with the traditional view. Good for him. I take moral responsibility to hinge on an action being caused by a person, but not with a mystical view of what a person is. |
| 9238 | Morality isn't based on reason; moral indignation is quite unlike disapproval of irrationality [Frankfurt] |
| Full Idea: The ultimate warrant for moral principles cannot be found in reason. The sort of opprobrium that attaches to moral transgressions is quite unlike the sort of opprobrium that attaches to the requirements of reason. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 2.5 n6) | |
| A reaction: More like a piece of evidence than a proper argument. We may not feel indignant if someone fails a maths exam, but we might if they mess up the arithmetic of our bank account, even though they meant well. |
| 9232 | It is by caring about things that we infuse the world with importance [Frankfurt] |
| Full Idea: It is by caring about things that we infuse the world with importance. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 1.10) | |
| A reaction: This book is a lovely attempt at getting to the heart of where values come from. 'Football isn't a matter of life and death; it's more important than that' - Bill Shankly (manager of Liverpool). Frankfurt is right. |
| 9234 | If you don't care about at least one thing, you can't find reasons to care about anything [Frankfurt] |
| Full Idea: It is not possible for a person who does not already care at least about something to discover reasons for caring about anything. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 1.11) | |
| A reaction: This is the key idea of this lovely book. Without a glimmer of love somewhere, it is not possible to bootstrap a meaningful life. The glimmer of caring about one thing is transferable. See the Ancient Mariner and the watersnake. |
| 9229 | What is worthwhile for its own sake alone may be worth very little [Frankfurt] |
| Full Idea: What is worth having or worth doing for its own sake alone may nonetheless be worth very little. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 1.5) | |
| A reaction: That is one of my cherished notions sunk without trace! Aristotle's idea that ends are what matter, not means, always struck me as crucial. But Frankfurt is right. Collecting trivia is done for its own sake. Great tasks are performed as a means. |
| 9233 | Our criteria for evaluating how to live offer an answer to the problem [Frankfurt] |
| Full Idea: Identifying the criteria to be employed in evaluating various ways of living is also tantamount to providing an answer to the question of how to live. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 1.10) | |
| A reaction: Presumably critical reflection is still possible about those criteria, even though he implies that they just arise out of you (in a rather Nietzschean way). The fear is that critical reflection on basic criteria kills in infant in its cradle. |
| 9235 | Rather than loving things because we value them, I think we value things because we love them [Frankfurt] |
| Full Idea: It is often understood that we begin loving things because we are struck by their value. ..However, what I have in mind is rather that what we love necessarily acquires value for us because we love it. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 2.3) | |
| A reaction: The uneasy thought here is that this makes value much less rational. If you love because you value, you could probably give reasons for the value. If love comes first it must be instinctive. He says he loved his children before they were born. |
| 9236 | Love can be cool, and it may not involve liking its object [Frankfurt] |
| Full Idea: It is not among the defining features of love that it must be hot rather than cool, ..and nor is it essential that a person like what he loves. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 2.4) | |
| A reaction: An interesting pair of observations. The greatness of love would probably be measured by length, or by sacrifice. Extreme heat makes us a little suspicious. It would be hard to love something that was actually disliked. |
| 9237 | The paradigm case of pure love is not romantic, but that between parents and infants [Frankfurt] |
| Full Idea: Relationships that are primarily romantic or sexual do not provide very authentic or illuminating paradigms of love. ...The love of parents for their small children comes closest to offering recognizably pure instances of love. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 2.4) | |
| A reaction: Excellent. Though perhaps a relationships which began romantically might settle into something like the more 'pure' love that he has in mind. Such a relationship must, I trust, be possible between adults. |
| 9239 | I value my children for their sake, but I also value my love for them for its own sake [Frankfurt] |
| Full Idea: Beside the fact that my children are important to me for their own sakes, there is the additional fact that loving my children is important to me for its own sake. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 2.7) | |
| A reaction: This is at the heart of Frankfurt's thesis, that love is the bedrock of our values in life, and we therefore all need to love in order to generate any values in our life, quite apart from what our love is directed at. Nice thought. |
| 9227 | We might not choose a very moral life, if the character or constitution was deficient [Frankfurt] |
| Full Idea: People who are scrupulously moral may nonetheless be destined by deficiencies of character or of constitution to lead lives that no reasonable person would freely choose. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 1.2) | |
| A reaction: This fairly firmly refutes any Greek dream that all there is to happiness is leading a virtuous life. Frankfurt is with Aristotle more than with the Stoics. It would be tempting to sacrifice virtue to get a sunny character and good health. |
| 9230 | People want to fulfill their desires, but also for their desires to be sustained [Frankfurt] |
| Full Idea: Besides wanting to fulfil his desire, the person who cares about what he desires wants something else as well: he wants the desire to be sustained. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 1.6) | |
| A reaction: Plato, in 'Gorgias', makes this fact sound like a nightmare, resembling drug addiction, but in Frankfurt's formulation it looks like a good thing. If you want to make your family happy because you love them, you would dread finding your love had died. |
| 9241 | Loving oneself is not a failing, but is essential to a successful life [Frankfurt] |
| Full Idea: Far from demonstrating a flaw in character or being a sign of weakness, coming to love oneself is the deepest and most essential - and by no means the most readily attainable - achievement of a serious and successful life. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 2.14) | |
| A reaction: Obviously it will be necessary to dilineate the healthy form of self-love, which Frankfurt attempts to do. Ruthless vanity and self-seeking certainly look like the worst possible weaknesses of character. With that proviso, he is right. |
| 9300 | Boredom is serious, not just uncomfortable; it threatens our psychic survival [Frankfurt] |
| Full Idea: Boredom is a serious matter. It is not a condition that we seek to avoid just because we do not find it enjoyable. ..It threatens the very continuation of conscious mental life. ..Avoiding bored is a primitive urge for psychic survival. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 2.8) | |
| A reaction: Presumably nihilism will flood into the emptiness created by boredom. Frankfurt will see it as a lack of love for anything in your life, and hence an absence of value. Frankfurt is very good. |
| 9231 | Freedom needs autonomy (rather than causal independence) - embracing our own desires and choices [Frankfurt] |
| Full Idea: What counts as far as freedom goes is not causal independence, but autonomy. It is a matter of whether we are active rather than passive in our motives and choices, whether those are what we really want, and not alien to us. | |
| From: Harry G. Frankfurt (The Reasons of Love [2005], 1.8) | |
| A reaction: This is why setting your own targets is excellent, but having targets set for you by authorities is pernicious. These kind of principles need to be clear before any plausible theory of liberalism can be developed. |
| 9363 | Science seeks classification which will discover laws, essences, and predictions [Lewis,CI] |
| Full Idea: The scientific search is for such classification as will make it possible to correlate appearance and behaviour, to discover law, to penetrate to the "essential nature" of things in order that behaviour may become predictable. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.368) | |
| A reaction: Modern scientific essentialists no longer invoke scare quotes, and I think we should talk of the search for the 'mechanisms' which explain behaviour, but Lewis seems to have been sixty years ahead of his time. |