17 ideas
| 23367 | Even pointing a finger should only be done for a reason [Epictetus] |
| Full Idea: Philosophy says it is not right even to stretch out a finger without some reason. | |
| From: Epictetus (fragments/reports [c.57], 15) | |
| A reaction: The key point here is that philosophy concerns action, an idea on which Epictetus is very keen. He rather despise theory. This idea perfectly sums up the concept of the wholly rational life (which no rational person would actually want to live!). |
| 22334 | Analysis must include definitions, search for simples, concept analysis, and Kant's analysis [Glock] |
| Full Idea: Under 'analysis' a minimum would include the Socratic quest for definitions, Descartes' search for simple natures, the empiricists' psychological resolution of complex ideas, and Kant's 'transcendental' analysis of our cognitive capacities. | |
| From: Hans-Johann Glock (What is Analytic Philosophy? [2008], 6.1) | |
| A reaction: This has always struck me, and I find the narrow focus on modern logic a very distorted idea of the larger project. The aim, I think, is to understand by taking things apart, in the spirit of figuring out how a watch works. |
| 10301 | The axiom of choice is controversial, but it could be replaced [Shapiro] |
| Full Idea: The axiom of choice has a troubled history, but is now standard in mathematics. It could be replaced with a principle of comprehension for functions), or one could omit the variables ranging over functions. | |
| From: Stewart Shapiro (Higher-Order Logic [2001], n 3) |
| 10588 | First-order logic is Complete, and Compact, with the Löwenheim-Skolem Theorems [Shapiro] |
| Full Idea: Early study of first-order logic revealed a number of important features. Gödel showed that there is a complete, sound and effective deductive system. It follows that it is Compact, and there are also the downward and upward Löwenheim-Skolem Theorems. | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.1) |
| 10298 | Some say that second-order logic is mathematics, not logic [Shapiro] |
| Full Idea: Some authors argue that second-order logic (with standard semantics) is not logic at all, but is a rather obscure form of mathematics. | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.4) |
| 10299 | If the aim of logic is to codify inferences, second-order logic is useless [Shapiro] |
| Full Idea: If the goal of logical study is to present a canon of inference, a calculus which codifies correct inference patterns, then second-order logic is a non-starter. | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.4) | |
| A reaction: This seems to be because it is not 'complete'. However, moves like plural quantification seem aimed at capturing ordinary language inferences, so the difficulty is only that there isn't a precise 'calculus'. |
| 10300 | Logical consequence can be defined in terms of the logical terminology [Shapiro] |
| Full Idea: Informally, logical consequence is sometimes defined in terms of the meanings of a certain collection of terms, the so-called 'logical terminology'. | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.4) | |
| A reaction: This seems to be a compositional account, where we build a full account from an account of the atomic bits, perhaps presented as truth-tables. |
| 10290 | Second-order variables also range over properties, sets, relations or functions [Shapiro] |
| Full Idea: Second-order variables can range over properties, sets, or relations on the items in the domain-of-discourse, or over functions from the domain itself. | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.1) |
| 10590 | Up Löwenheim-Skolem: if natural numbers satisfy wffs, then an infinite domain satisfies them [Shapiro] |
| Full Idea: Upward Löwenheim-Skolem: if a set of first-order formulas is satisfied by a domain of at least the natural numbers, then it is satisfied by a model of at least some infinite cardinal. | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.1) |
| 10296 | The Löwenheim-Skolem Theorems fail for second-order languages with standard semantics [Shapiro] |
| Full Idea: Both of the Löwenheim-Skolem Theorems fail for second-order languages with a standard semantics | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.3.2) |
| 10297 | The Löwenheim-Skolem theorem seems to be a defect of first-order logic [Shapiro] |
| Full Idea: The Löwenheim-Skolem theorem is usually taken as a sort of defect (often thought to be inevitable) of the first-order logic. | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.4) | |
| A reaction: [He is quoting Wang 1974 p.154] |
| 10292 | Downward Löwenheim-Skolem: if there's an infinite model, there is a countable model [Shapiro] |
| Full Idea: Downward Löwenheim-Skolem: a finite or denumerable set of first-order formulas that is satisfied by a model whose domain is infinite is satisfied in a model whose domain is the natural numbers | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.1) |
| 10294 | Second-order logic has the expressive power for mathematics, but an unworkable model theory [Shapiro] |
| Full Idea: Full second-order logic has all the expressive power needed to do mathematics, but has an unworkable model theory. | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.1) | |
| A reaction: [he credits Cowles for this remark] Having an unworkable model theory sounds pretty serious to me, as I'm not inclined to be interested in languages which don't produce models of some sort. Surely models are the whole point? |
| 10591 | Logicians use 'property' and 'set' interchangeably, with little hanging on it [Shapiro] |
| Full Idea: In studying second-order logic one can think of relations and functions as extensional or intensional, or one can leave it open. Little turns on this here, and so words like 'property', 'class', and 'set' are used interchangeably. | |
| From: Stewart Shapiro (Higher-Order Logic [2001], 2.2.1) | |
| A reaction: Important. Students of the metaphysics of properties, who arrive with limited experience of logic, are bewildered by this attitude. Note that the metaphysics is left wide open, so never let logicians hijack the metaphysical problem of properties. |
| 22332 | German and British idealism is not about individual ideas, but the intelligibility of reality [Glock] |
| Full Idea: Neither German nor British Idealism reduced reality to episodes in the minds of individuals. Instsead, they insisted that reality is intelligible only because it is a manifestation of a divine spirit or rational principle. | |
| From: Hans-Johann Glock (What is Analytic Philosophy? [2008], 5.2) | |
| A reaction: They standardly reject Berkeley. Such Idealism seems either to be the design argument for God's existence, or neo-Stoicism (in its claim that nature is rational). Why not just say that nature seems to be intelligible, and stop there? |
| 22336 | We might say that the family resemblance is just a consequence of meaning-as-use [Glock] |
| Full Idea: Against Wittgenstein's family resemblance view one might evoke his own idea that the meaning of a word is its use, and that diversity of use entails diversity of meaning. | |
| From: Hans-Johann Glock (What is Analytic Philosophy? [2008], 8.2) | |
| A reaction: Wittgenstein might just accept the point. Diversity of concepts reflects diversity of usage. But how do you distinguish 'football is a game' from 'oy, what's your game?'. How does usage distinguish metaphorical from literal (if it does)? |
| 22335 | The variety of uses of 'game' may be that it has several meanings, and isn't a single concept [Glock] |
| Full Idea: The proper conclusion to draw from the fact that we explain 'game' in a variety of different ways is that it is not a univocal term, but has different, albeit related, meanings. | |
| From: Hans-Johann Glock (What is Analytic Philosophy? [2008], 8.2) | |
| A reaction: [He cites Rundle 1990] Potter says Wittgenstein insisted that 'game' is a single concept. 'Game' certainly slides off into metaphor, as in 'are you playing games with me?'. The multivocal view would still meet family resemblance on a narrower range. |