20 ideas
| 18739 | Three stages of philosophical logic: syntactic (1905-55), possible worlds (1963-85), widening (1990-) [Horsten/Pettigrew] |
| Full Idea: Three periods can be distinguished in philosophical logic: the syntactic stage, from Russell's definite descriptions to the 1950s, the dominance of possible world semantics from the 50s to 80s, and a current widening of the subject. | |
| From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 1) | |
| A reaction: [compressed] I've read elsewhere that the arrival of Tarski's account of truth in 1933, taking things beyond the syntactic, was also a landmark. |
| 18741 | Logical formalization makes concepts precise, and also shows their interrelation [Horsten/Pettigrew] |
| Full Idea: Logical formalization forces the investigator to make the central philosophical concepts precise. It can also show how some philosophical concepts and objects can be defined in terms of others. | |
| From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 2) | |
| A reaction: This is the main rationale of the highly formal and mathematical approach to such things. The downside is when you impose 'precision' on language that was never intended to be precise. |
| 18744 | Models are sets with functions and relations, and truth built up from the components [Horsten/Pettigrew] |
| Full Idea: A (logical) model is a set with functions and relations defined on it that specify the denotation of the non-logical vocabulary. A series of recursive clauses explicate how truth values of complex sentences are compositionally determined from the parts. | |
| From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 3) | |
| A reaction: See the ideas on 'Functions in logic' and 'Relations in logic' (in the alphabetical list) to expand this important idea. |
| 18740 | If 'exist' doesn't express a property, we can hardly ask for its essence [Horsten/Pettigrew] |
| Full Idea: If there is indeed no property of existence that is expressed by the word 'exist', then it makes no sense to ask for its essence. | |
| From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 2) | |
| A reaction: As far as I can tell, this was exactly Aristotle's conclusion, so he skirted round the question of 'being qua being', and focused on the nature of objects instead. Grand continental talk of 'Being' doesn't sound very interesting. |
| 18745 | A Tarskian model can be seen as a possible state of affairs [Horsten/Pettigrew] |
| Full Idea: A Tarskian model can in a sense be seen as a model of a possible state of affairs. | |
| From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 3) | |
| A reaction: I include this remark to show how possible worlds semantics built on the arrival of model theory. |
| 18747 | The 'spheres model' was added to possible worlds, to cope with counterfactuals [Horsten/Pettigrew] |
| Full Idea: The notion of a possible worlds model was extended (resulting in the concept of a 'spheres model') in order to obtain a satisfactory logical treatment of counterfactual conditional sentences. | |
| From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 4) | |
| A reaction: Thus we add 'centred' worlds, and an 'actual' world, to the loose original model. It is important to remember when we discuss 'close' worlds that we are then committed to these presuppositions. |
| 18748 | Epistemic logic introduced impossible worlds [Horsten/Pettigrew] |
| Full Idea: The idea of 'impossible worlds' was introduced into epistemic logic. | |
| From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 4) | |
| A reaction: Nathan Salmon seems interested in their role in metaphysics (presumably in relation to Meinongian impossible objects, like circular squares, which must necessarily be circular). |
| 18746 | Possible worlds models contain sets of possible worlds; this is a large metaphysical commitment [Horsten/Pettigrew] |
| Full Idea: Each possible worlds model contains a set of possible worlds. For this reason, possible worlds semantics is often charged with smuggling in heavy metaphysical commitments. | |
| From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 3) | |
| A reaction: To a beginner it looks very odd that you should try to explain possibility by constructing a model of it in terms of 'possible' worlds. |
| 18750 | Using possible worlds for knowledge and morality may be a step too far [Horsten/Pettigrew] |
| Full Idea: When the possible worlds semantics were further extended to model notions of knowledge and of moral obligation, the application was beginning to look distinctly forced and artificial. | |
| From: Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 5) | |
| A reaction: They accept lots of successes in modelling necessity and time. |
| 19419 | Not all of perception is accompanied by consciousness [Leibniz] |
| Full Idea: I do not think that the Cartesians have ever proved or can prove that every perception is accompanied by consciousness. | |
| From: Gottfried Leibniz (Principle of Life and Plastic Natures [1705], p.195) | |
| A reaction: This idea is very important in Leibniz, because non-conscious or barely conscious thoughts and perceptions explain a huge amount about behaviour, reality and morality. |
| 19421 | Souls act as if there were no bodies, and bodies act as if there were no souls [Leibniz] |
| Full Idea: Everything takes place in souls as if there were no body, and everything takes place in bodies as if there were no souls. | |
| From: Gottfried Leibniz (Principle of Life and Plastic Natures [1705], p.198) | |
| A reaction: I don't think I have ever encountered a modern thinker who accepts this view. Leibniz rejected Occasionalism, but his account depends entirely on the role of God, to set up the pre-established harmony. Why would God do that? |
| 19420 | Death and generation are just transformations of an animal, augmented or diminished [Leibniz] |
| Full Idea: Death, like generation, is only the transformation of the same animal, which is sometimes augmented and sometimes diminished. | |
| From: Gottfried Leibniz (Principle of Life and Plastic Natures [1705], p.195) | |
| A reaction: Leibniz has a very unusual view of death, since neither minds nor their bodies can ever be wholly destroyed. Death is a kind of shrinking. I suspect that he was wrong about that. |
| 19896 | It is not a law if not endorsed by the public [Hooker,R] |
| Full Idea: Laws they are not which public approbation hath not made so. | |
| From: Richard Hooker (Of the Laws of Ecclesiastical Polity [1593], I s.10), quoted by John Locke - Second Treatise of Government 134 n1 | |
| A reaction: Margaret Thatcher's Poll Tax, rejected by public rebellion, illustrates the point. |
| 19891 | Rule of law is superior to autonomy, because citizens can see what is expected [Hooker,R] |
| Full Idea: Men saw that to live by one man's will became the cause of all men's misery. This contrained them to come unto laws wherein all men might see their duty beforehand, and know the penalties of transgressing them. | |
| From: Richard Hooker (Of the Laws of Ecclesiastical Polity [1593], I s.10), quoted by John Locke - Second Treatise of Government 111 n1 | |
| A reaction: One British school has a single rule, that pupils 'shall always treat other people with respect'. Presumably the rulers, as well as the pupils, must decide when this is transgressed. The rule of law may be preferable. |
| 19897 | Human laws must accord with the general laws of Nature [Hooker,R] |
| Full Idea: Laws human must be made according to the general laws of Nature. | |
| From: Richard Hooker (Of the Laws of Ecclesiastical Polity [1593], III s.9), quoted by John Locke - Second Treatise of Government | |
| A reaction: The point simply seems to be that they won't get assent from the public if they are not in accord with natural justice. Positivists say you can make any damned law you like. |
| 19416 | Not all of matter is animated, any more than a pond full of living fish is animated [Leibniz] |
| Full Idea: It must not be said that each portion of matter is animated, just as we do not say that a pond full of fishes is an animated body, although a fish is. | |
| From: Gottfried Leibniz (Principle of Life and Plastic Natures [1705], p.190) | |
| A reaction: This is a particularly clear picture of the role of monads in matter. Monads are attached to bodies, which are entirely inanimate, but monads suffuse matter and give it its properties, like particularly bubbly champagne. Cf Idea 19422. |
| 19422 | Every particle of matter contains organic bodies [Leibniz] |
| Full Idea: There is no particle of matter which does not contain organic bodies. | |
| From: Gottfried Leibniz (Principle of Life and Plastic Natures [1705], p.198) | |
| A reaction: Cf Idea 19416. There seems to be an interaction problem here (solved, presumably, by pre-established harmony). The organic bodies are there to explain the active behaviour of matter, but the related matter seems intrinsically inert. |
| 17005 | Natural things observe certain laws, and things cannot do otherwise if they retain their forms [Hooker,R] |
| Full Idea: Things natural …do so necessarily observe their certain laws, that as long as they keep those forms which give them their being they cannot possibly be apt or inclinable to do otherwise than they do. | |
| From: Richard Hooker (Of the Laws of Ecclesiastical Polity [1593], 1.3.4), quoted by Marc Lange - Laws and Lawmakers 1.2 | |
| A reaction: Cited by some as the beginnings of the idea of 'laws of nature', but it is striking that Hooker says the laws are controlled by 'forms' (which are Aristotelian essences). This is an essentialist view of laws, not a regularity or divine power one. |
| 19418 | Mechanics shows that all motion originates in other motion, so there is a Prime Mover [Leibniz] |
| Full Idea: The maxim that there is no motion which has not its origin in another motion, according to the laws of mechanics, leads us again to the Prime Mover. | |
| From: Gottfried Leibniz (Principle of Life and Plastic Natures [1705], p.194) | |
| A reaction: This is Leibniz's endorsement (uncredited) to Aquinas's First Way. It is hard to see how the laws of mechanics could have anything to say about the origin of movement. And doesn't the law say that the motions of God need a mover? |
| 19417 | All substances are in harmony, even though separate, so they must have one divine cause [Leibniz] |
| Full Idea: My system of Pre-established Harmony furnishes a new proof of God's existence, since it is manifest that the agreement of so many substances, of which the one has no influence upon the other, could only come from a general cause on which they all depend. | |
| From: Gottfried Leibniz (Principle of Life and Plastic Natures [1705], p.192) | |
| A reaction: Adjacent harmony seems self-explanatory, but remote harmony is interesting evidence for God. Hence modern quantum non-locality should make us all wonder whether there is a deeper explanation. |