22 ideas
| 8952 | We reach 'reflective equilibrium' when intuitions and theory completely align [Fisher] |
| Full Idea: A state of 'reflective equilibrium' is when our theory and our intuitions become completely aligned | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 12.IV) | |
| A reaction: [Rawls made this concept famous] This is a helpful concept in trying to spell out the ideal which is the dream of believers in 'pure reason' - that there is a goal in which everything comes right. The problem is when people have different intuitions! |
| 8943 | Three-valued logic says excluded middle and non-contradition are not tautologies [Fisher] |
| Full Idea: In three-valued logic (L3), neither the law of excluded middle (p or not-p), nor the law of non-contradiction (not(p and not-p)) will be tautologies. If p has the value 'indeterminate' then so will not-p. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.I) | |
| A reaction: I quite accept that the world is full of indeterminate propositions, and that excluded middle and non-contradiction can sometimes be uncertain, but I am reluctant to accept that what is being offered here should be called 'logic'. |
| 8945 | Fuzzy logic has many truth values, ranging in fractions from 0 to 1 [Fisher] |
| Full Idea: In fuzzy logic objects have properties to a greater or lesser degree, and truth values are given as fractions or decimals, ranging from 0 to 1. Not-p is defined as 1-p, and other formula are defined in terms of maxima and minima for sets. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.II) | |
| A reaction: The question seems to be whether this is actually logic, or a recasting of probability theory. Susan Haack attacks it. If logic is the study of how truth is preserved as we move between propositions, then 0 and 1 need a special status. |
| 8951 | Classical logic is: excluded middle, non-contradiction, contradictions imply all, disjunctive syllogism [Fisher] |
| Full Idea: For simplicity, we can say that 'classical logic' amounts to the truth of four sentences: 1) either p or not-p; 2) it is not the case that both p and not-p; 3) from p and not-p, infer q; 4) from p or q and not-p, infer q. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 12.I) | |
| A reaction: [She says there are many ways of specifying classical logic] Intuition suggests that 2 and 4 are rather hard to dispute, while 1 is ignoring some grey areas, and 3 is totally ridiculous. There is, of course, plenty of support for 3! |
| 8950 | Logic formalizes how we should reason, but it shouldn't determine whether we are realists [Fisher] |
| Full Idea: Even if one is inclined to be a realist about everything, it is hard to see why our logic should be the determiner. Logic is supposed to formalize how we ought to reason, but whether or not we should be realists is a matter of philosophy, not logic. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 09.I) | |
| A reaction: Nice to hear a logician saying this. I do not see why talk in terms of an object is a commitment to its existence. We can discuss the philosopher's stone, or Arthur's sword, or the Loch Ness monster, or gravitinos, with degrees of commitment. |
| 8946 | We could make our intuitions about heaps precise with a million-valued logic [Fisher] |
| Full Idea: We could construct a 1,000,000-valued logic that would allow our intuitions concerning a heap to vary exactly with the amount of sand in the heap. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008]) | |
| A reaction: Presumably only an infinite number of grains of sand would then produce a true heap, and even one grain would count as a bit of a heap, which must both be wrong, so I can't see this helping much. |
| 23664 | Powers are quite distinct and simple, and so cannot be defined [Reid] |
| Full Idea: Power is a thing so much of its own kind, and so simple in its nature, as to admit of no logical definition. | |
| From: Thomas Reid (Essays on Active Powers 1: Active power [1788], 1) | |
| A reaction: True. And this makes Powers ideally suited for the role of primitives in a metaphysics of nature. |
| 23669 | Thinkers say that matter has intrinsic powers, but is also passive and acted upon [Reid] |
| Full Idea: Those philosophers who attribute to matter the power of gravitation, and other active powers, teach us, at the same time, that matter is a substance altogether inert, and merely passive; …that those powers are impressed on it by some external cause. | |
| From: Thomas Reid (Essays on Active Powers 1: Active power [1788], 6) | |
| A reaction: This shows the dilemma of the period, when 'laws of nature' were imposed on passive matter by God, and yet gravity and magnetism appeared as inherent properties of matter. |
| 23666 | It is obvious that there could not be a power without a subject which possesses it [Reid] |
| Full Idea: It is evident that a power is a quality, and cannot exist without a subject to which it belongs. That power may exist without any being or subject to which that power may be attributed, is an absurdity, shocking to every man of common understanding. | |
| From: Thomas Reid (Essays on Active Powers 1: Active power [1788], 1) | |
| A reaction: This is understandble in the 18th C, when free-floating powers were inconceivable, but now that we have fields and plasmas and whatnot, we can't rule out pure powers as basic. However, I incline to agree with Reid. Matter is active. |
| 8944 | Vagueness can involve components (like baldness), or not (like boredom) [Fisher] |
| Full Idea: Vague terms come in at least two different kinds: those whose constituent parts come in discrete packets (bald, rich, red) and those that don't (beauty, boredom, niceness). | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.II) | |
| A reaction: The first group seem to be features of the external world, and the second all occur in the mind. Baldness may be vague, but presumably hairs are (on the whole) not. Nature doesn't care whether someone is actually 'bald' or not. |
| 8941 | We can't explain 'possibility' in terms of 'possible' worlds [Fisher] |
| Full Idea: Explaining 'it is possible that p' by saying p is true in at least one possible world doesn't get me very far. If I don't understand what possibility is, then appealing to possible worlds is not going to do me much good. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 06.III) | |
| A reaction: This seems so blatant that I assume friends of possible worlds will have addressed the problem. Note that you will also need to understand 'possible' to define necessity as 'true in all possible worlds'. Necessarily-p is not-possibly-not-p. |
| 8947 | If all truths are implied by a falsehood, then not-p might imply both q and not-q [Fisher] |
| Full Idea: If all truths are implied by a falsehood, then 'if there are no trees in the park then there is no shade' and 'if there are no trees in the park there is plenty of shade' both come out as true. Intuitively, though, the second one is false. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 08.I) | |
| A reaction: The rule that a falsehood implies all truths must be the weakest idea in classical logic, if it actually implies a contradiction. This means we must take an interest in relevance logics. |
| 8949 | In relevance logic, conditionals help information to flow from antecedent to consequent [Fisher] |
| Full Idea: A good account of relevance logic suggests that a conditional will be true when the flow of information is such that a conditional is the device that helps information to flow from the antecedent to the consequent. | |
| From: Jennifer Fisher (On the Philosophy of Logic [2008], 08.III) | |
| A reaction: Hm. 'If you are going out, you'll need an umbrella'. This passes on information about 'out', but also brings in new information. 'If you are going out, I'm leaving you'. What flows is an interpretation of the antecedent. Tricky. |
| 23665 | Consciousness is the power of mind to know itself, and minds are grounded in powers [Reid] |
| Full Idea: Consciousness is that power of the mind by which it has an immediate knowledge of its own operations. …Every operation of the mind is the exertion of some power of the mind. | |
| From: Thomas Reid (Essays on Active Powers 1: Active power [1788], 1) | |
| A reaction: I strongly favour this account of the mind and consciousness in terms of powers, because they give the best basis for their dynamic nature, and seem to be primitives which terminate all of our explanations. Science identifies the powers for us. |
| 23668 | Our own nature attributes free determinations to our own will [Reid] |
| Full Idea: Every man is led by nature to attribute to himself the free determination of his own will, and to believe those events to be in his power which depend upon his will. | |
| From: Thomas Reid (Essays on Active Powers 1: Active power [1788], 5) | |
| A reaction: I'm happy to say we are all responsible for those actions which are caused by the conscious decisions of our own will (our mental decision mechanisms), but personally I would drop the word 'free', which adds nothing. We are not 'ultimately' responsible. |
| 20051 | Reid said that agent causation is a unique type of causation [Reid, by Stout,R] |
| Full Idea: Thomas Reid said that an agent's causing something involves a fundamentally different kind of causation from inanimate causing. | |
| From: report of Thomas Reid (Essays on Active Powers 1: Active power [1788]) by Rowland Stout - Action 4 'Agent' | |
| A reaction: I'm afraid the great philosopher of common sense got it wrong on this one. Introducing a new type of causation into our account of nature is crazy. |
| 13304 | Learned men gain more in one day than others do in a lifetime [Posidonius] |
| Full Idea: In a single day there lies open to men of learning more than there ever does to the unenlightened in the longest of lifetimes. | |
| From: Posidonius (fragments/reports [c.95 BCE]), quoted by Seneca the Younger - Letters from a Stoic 078 | |
| A reaction: These remarks endorsing the infinite superiority of the educated to the uneducated seem to have been popular in late antiquity. It tends to be the religions which discourage great learning, especially in their emphasis on a single book. |
| 8383 | Day and night are constantly conjoined, but they don't cause one another [Reid, by Crane] |
| Full Idea: A famous example of Thomas Reid: day regularly follows night, and night regularly follows day. There is therefore a constant conjunction between night and day. But day does not cause night, nor does night cause day. | |
| From: report of Thomas Reid (Essays on Active Powers 1: Active power [1788]) by Tim Crane - Causation 1.2.2 | |
| A reaction: Not a fatal objection to Hume, of course, because in the complex real world there are huge numbers of nested constant conjunctions. Night and the rotation of the Earth are conjoined. But how do you tell which constant conjunctions are causal? |
| 23667 | Regular events don't imply a cause, without an innate conviction of universal causation [Reid] |
| Full Idea: A train of events following one another ever so regularly, could never lead us to the notion of a cause, if we had not, from our constitution, a conviction of the necessity of a cause for every event. | |
| From: Thomas Reid (Essays on Active Powers 1: Active power [1788], 5) | |
| A reaction: Presumably a theist like Reid must assume that the actions of God are freely chosen, rather than necessities. It's hard to see why this principle should be innate in us, and hard to see why it must thereby be true. A bit Kantian, this idea. |
| 23670 | Scientists don't know the cause of magnetism, and only discover its regulations [Reid] |
| Full Idea: A Newtonian philosopher …confesses his ignorance of the true cause of magnetic motion, and thinks that his business, as a philosopher, is only to find from experiment the laws by which it is regulated in all cases. | |
| From: Thomas Reid (Essays on Active Powers 1: Active power [1788], 6) | |
| A reaction: Since there is a 'true cause', that implies that the laws don't actively 'regulate' the magnetism, but only describe its regularity, which I think is the correct view of laws. |
| 23671 | Laws are rules for effects, but these need a cause; rules of navigation don't navigate [Reid] |
| Full Idea: The laws of nature are the rules according to which the effects are produced; but there must be a cause which operates according to these rules. The rules of navigation never navigated a ship. | |
| From: Thomas Reid (Essays on Active Powers 1: Active power [1788], 6) | |
| A reaction: Very nice. No enquirer should be satisfied with merely discovering patterns; the point is to explain the patterns. |
| 20820 | Time is an interval of motion, or the measure of speed [Posidonius, by Stobaeus] |
| Full Idea: Posidonius defined time thus: it is an interval of motion, or the measure of speed and slowness. | |
| From: report of Posidonius (fragments/reports [c.95 BCE]) by John Stobaeus - Anthology 1.08.42 | |
| A reaction: Hm. Can we define motion or speed without alluding to time? Looks like we have to define them as a conjoined pair, which means we cannot fully understand either of them. |