21 ideas
2676 | Didactic argument starts from the principles of the subject, not from the opinions of the learner [Aristotle] |
Full Idea: Didactic arguments are those which reason from the principles appropriate to each branch of learning and not from the opinions of the answerer (for he who is learning must take things on trust). | |
From: Aristotle (Sophistical Refutations [c.331 BCE], 165b01) |
2675 | Reasoning is a way of making statements which makes them lead on to other statements [Aristotle] |
Full Idea: Reasoning is based on certain statements made in such a way as necessarily to cause the assertion of things other than those statements and as a result of those statements. | |
From: Aristotle (Sophistical Refutations [c.331 BCE], 165a01) |
2677 | Dialectic aims to start from generally accepted opinions, and lead to a contradiction [Aristotle] |
Full Idea: Dialectical arguments are those which, starting from generally accepted opinions, reason to establish a contradiction. | |
From: Aristotle (Sophistical Refutations [c.331 BCE], 165b03) |
2674 | Competitive argument aims at refutation, fallacy, paradox, solecism or repetition [Aristotle] |
Full Idea: Those who compete and contend in argument aim at five objects: refutation, fallacy, paradox, solecism, and the reduction of one's opponent to a state of babbling, that is, making him say the same thing over and over again. | |
From: Aristotle (Sophistical Refutations [c.331 BCE], 165b15) |
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. |
16967 | 'Are Coriscus and Callias at home?' sounds like a single question, but it isn't [Aristotle] |
Full Idea: If you ask 'Are Coriscus and Callias at home or not at home?', whether they are both at home or not there, the number of propositions is more than one. For if the answer is true, it does not follow that the question is a single one. | |
From: Aristotle (Sophistical Refutations [c.331 BCE], 176a08) | |
A reaction: [compressed] Aristotle is saying that some questions should not receive a 'yes' or 'no' answer, because they are equivocal. Arthur Prior cites this passage, on 'and'. Ordinary use of 'and' need not be the logical use of 'and'. |
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. |
8784 | Neo-logicism founds arithmetic on Hume's Principle along with second-order logic [Hale/Wright] |
Full Idea: The result of joining Hume's Principle to second-order logic is a consistent system which is a foundation for arithmetic, in the sense that all the fundamental laws of arithmetic are derivable within it as theorems. This seems a vindication of logicism. | |
From: B Hale / C Wright (Logicism in the 21st Century [2007], 1) | |
A reaction: The controversial part seems to be second-order logic, which Quine (for example) vigorously challenged. The contention against most attempts to improve Frege's logicism is that they thereby cease to be properly logical. |
8787 | The Julius Caesar problem asks for a criterion for the concept of a 'number' [Hale/Wright] |
Full Idea: The Julius Caesar problem is the problem of supplying a criterion of application for 'number', and thereby setting it up as the concept of a genuine sort of object. (Why is Julius Caesar not a number?) | |
From: B Hale / C Wright (Logicism in the 21st Century [2007], 3) | |
A reaction: One response would be to deny that numbers are objects. Another would be to derive numbers from their application in counting objects, rather than the other way round. I suspect that the problem only real bothers platonists. Serves them right. |
8788 | Logicism is only noteworthy if logic has a privileged position in our ontology and epistemology [Hale/Wright] |
Full Idea: It is only if logic is metaphysically and epistemologically privileged that a reduction of mathematical theories to logical ones can be philosophically any more noteworthy than a reduction of any mathematical theory to any other. | |
From: B Hale / C Wright (Logicism in the 21st Century [2007], 8) | |
A reaction: It would be hard to demonstrate this privileged position, though intuitively there is nothing more basic in human rationality. That may be a fact about us, but it doesn't make logic basic to nature, which is where proper reduction should be heading. |
8783 | Logicism might also be revived with a quantificational approach, or an abstraction-free approach [Hale/Wright] |
Full Idea: Two modern approaches to logicism are the quantificational approach of David Bostock, and the abstraction-free approach of Neil Tennant. | |
From: B Hale / C Wright (Logicism in the 21st Century [2007], 1 n2) | |
A reaction: Hale and Wright mention these as alternatives to their own view. I merely catalogue them for further examination. My immediate reaction is that Bostock sounds hopeless and Tennant sounds interesting. |
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. |
16149 | Generic terms like 'man' are not substances, but qualities, relations, modes or some such thing [Aristotle] |
Full Idea: 'Man', and every generic term, denotes not an individual substance but a quality or relation or mode or something of the kind. | |
From: Aristotle (Sophistical Refutations [c.331 BCE], 179a01) | |
A reaction: This is Aristotle's denial that species constitutes the essence of anything. I take 'man' to be a categorisation of individuals, and is ontologically nothing at all in its own right. |
11840 | Only if two things are identical do they have the same attributes [Aristotle] |
Full Idea: It is only to things which are indistinguishable and one in essence [ousia] that all the same attributes are generally held to belong. | |
From: Aristotle (Sophistical Refutations [c.331 BCE], 179a37) | |
A reaction: This simply IS Leibniz's Law (to which I shall from now on quietly refer to as 'Aristotle's Law'). It seems that it just as plausible to translate 'ousia' as 'being' rather than 'essence'. 'Indistinguishable' and 'one in ousia' are not the same. |
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. |
8786 | One first-order abstraction principle is Frege's definition of 'direction' in terms of parallel lines [Hale/Wright] |
Full Idea: An example of a first-order abstraction principle is Frege's definition of 'direction' in terms of parallel lines; a higher-order example (which refers to first-order predicates) defines 'equinumeral' in terms of one-to-one correlation (Hume's Principle). | |
From: B Hale / C Wright (Logicism in the 21st Century [2007], 1) | |
A reaction: [compressed] This is the way modern logicians now treat abstraction, but abstraction principles include the elusive concept of 'equivalence' of entities, which may be no more than that the same adjective ('parallel') can be applied to them. |