| 5772 | The idea of a variable is fundamental [Russell] |
| Full Idea: I take the notion of the variable as fundamental. | |
| From: Bertrand Russell (On Denoting [1905], p.42) | |
| A reaction: A key idea of twentieth century philosophy, derived from Frege and handed on to Quine. A universal term, such as 'horse', is a variable, for which any particular horse can be its value. You can calculate using x, and generalise about horses. |
| 14114 | Variables don't stand alone, but exist as parts of propositional functions [Russell] |
| Full Idea: A variable is not any term simply, but any term as entering into a propositional function. | |
| From: Bertrand Russell (The Principles of Mathematics [1903], §093) | |
| A reaction: So we should think of variables entirely by their role, rather than as having a semantics of their own (pace Kit Fine? - though see Russell §106, p.107). |
| 17699 | Variables are auxiliary notions, and not part of the 'eternal' essence of logic [Schönfinkel] |
| Full Idea: A variable in a proposition of logic ....has the status of a mere auxiliary notion that is really inappropriate to the constant, 'eternal' essence of the propositions of logic. | |
| From: Moses Schönfinkel (Building Blocks of Mathematical Logic [1924], §1) | |
| A reaction: He presumably thinks that what the variables stand for (and he mentions 'argument places' and 'operators') will be included in the essence. My attention was caught by the thought that he takes logic to have an essence. |
| 7784 | 'Object' is a pseudo-concept, properly indicated in logic by the variable x [Wittgenstein] |
| Full Idea: The variable name ‘x’ is the proper sign of the pseudo-concept object. Wherever the word ‘object’ (‘thing’, ‘entity’, etc.) is rightly used, it is expressed in logical symbolism by the variable name. | |
| From: Ludwig Wittgenstein (Tractatus Logico-Philosophicus [1921], 4.1272) | |
| A reaction: This seems to be the germ of Quine's famous dictum (Idea 1610). I am not persuaded that because logic must handle an object as a variable, that it follows that we are dealing with a pseudo-concept. Let logic limp behind life. |
| 12221 | 'Corner quotes' (quasi-quotation) designate 'whatever these terms designate' [Quine] |
| Full Idea: A 'quasi-quotation' [corner quotes, Quine quotes] designates that (unspecified) expression which is obtained from the contents of the corners by replacing the Greek letters by the (unspecified) expressions which they designate. | |
| From: Willard Quine (Mathematical Logic (revised) [1940], 1.6) | |
| A reaction: Filed under 'variables', as they seem to be variables that can refer to actual expressions, like algebra. Quine was determined to distinguish clearly between 'mention' and 'use'. 'Half-hearted substitutional quantification', says Fine. |
| 1618 | We study bound variables not to know reality, but to know what reality language asserts [Quine] |
| Full Idea: We look to bound variables in connection with ontology not in order to know what there is, but in order to know what a given remark or doctrine, ours or someone else's, says there is. | |
| From: Willard Quine (On What There Is [1948], p.15) |
| 13839 | Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers [Hacking] |
| Full Idea: For some purposes the variables of first-order logic can be regarded as prepositions and place-holders that could in principle be dispensed with, say by a system of arrows indicating what places fall in the scope of which quantifier. | |
| From: Ian Hacking (What is Logic? [1979], §11) | |
| A reaction: I tend to think of variables as either pronouns, or as definite descriptions, or as temporary names, but not as prepositions. Must address this new idea... |
| 17558 | Variables are just like pronouns; syntactic explanations get muddled over dummy letters [Inwagen] |
| Full Idea: Explanations in terms of syntax do not satisfactorily distinguish true variables from dummy or schematic letters. Identifying variables with pronouns, however, provides a genuine explanation of what variables are. | |
| From: Peter van Inwagen (Material Beings [1990], 02) | |
| A reaction: I like this because it shows that our ordinary thought and speech use variables all the time ('I've forgotten something - what was it?'). He says syntax is fine for maths, but not for ordinary understanding. |
| 9148 | I think of variables as objects rather than as signs [Fine,K] |
| Full Idea: It is natural nowadays to think of variables as a certain kind of sign, but I wish to think of them as a certain kind of object. | |
| From: Kit Fine (Cantorian Abstraction: Recon. and Defence [1998], §2) | |
| A reaction: Fine has a theory based on 'arbitrary objects', which is a rather charming idea. The cell of a spreadsheet is a kind of object, I suppose. A variable might be analogous to a point in space, where objects can locate themselves. |
| 15590 | It seemed that Frege gave the syntax for variables, and Tarski the semantics, and that was that [Fine,K] |
| Full Idea: Once Frege had provided a clear syntactic account of variables and once Tarski had supplemented this with a rigorous semantic account, it would appear that there was nothing more of significance to be said. | |
| From: Kit Fine (Semantic Relationism [2007], 1) | |
| A reaction: He later remarks that there are now three semantic accounts: the Tarskian, the instantial, and the algebraic [see xref ideas]. He offers a fourth account in his Semantic Relationism. This grows from his puzzles about variables. |
| 15591 | In separate expressions variables seem identical in role, but in the same expression they aren't [Fine,K] |
| Full Idea: When we consider the semantic role of 'x' and 'y' in two distinct expressions x>0 and y>0, their semantic roles seems the same. But in the same expression, such as x>y, their roles seem to be different. | |
| From: Kit Fine (Semantic Relationism [2007], 1.A) | |
| A reaction: [compressed] This new puzzle about variables leads Fine to say that the semantics of variables, and other expressions, is not intrinsic to them, but depends on their external relations. Variables denote any term - unless another variable got there first. |
| 15592 | The usual Tarskian interpretation of variables is to specify their range of values [Fine,K] |
| Full Idea: The usual Tarskian way of indicating how a variable is to be interpreted is to simply specify its range of values. | |
| From: Kit Fine (Semantic Relationism [2007], 1.B) |
| 15593 | Variables can be viewed as special terms - functions taking assignments into individuals [Fine,K] |
| Full Idea: The alternative Tarskian way of indicating how a variable is to be interpreted is that a variable x will be a special case of the semantic value of the term; it will be a function which takes each assignment into the individual which it assigns to x. | |
| From: Kit Fine (Semantic Relationism [2007], 1.B) |
| 15595 | The 'algebraic' account of variables reduces quantification to the algebra of its component parts [Fine,K] |
| Full Idea: In the 'algebraic' approach to variables, we move from a quantified sentence to the term specifying a property (the λ-term), and then reducing to the algebraic operations for atomic formulas. | |
| From: Kit Fine (Semantic Relationism [2007], 1.C) | |
| A reaction: [Bealer is a source for this view] Fine describes it as an 'algebra of operations'. I presume this is a thoroughly formalist approach to the matter, which doesn't seem to get to the heart of the semantic question. |
| 15594 | 'Instantial' accounts of variables say we grasp arbitrary instances from their use in quantification [Fine,K] |
| Full Idea: According to the 'instantial' approach to variables, a closed quantified sentence is to be understood on the basis of one of its instances; from an understanding of an instance we understand satisfaction by an arbitrary individual. | |
| From: Kit Fine (Semantic Relationism [2007], 1.D) | |
| A reaction: Fine comments that this is intuitively plausible, but not very precise, because it depends on 'abstraction' of the individual from the expression. |
| 15409 | All occurrences of variables in atomic formulas are free [Burgess] |
| Full Idea: All occurrences of variables in atomic formulas are free. | |
| From: John P. Burgess (Philosophical Logic [2009], 1.7) |
| 13696 | When a variable is 'free' of the quantifier, the result seems incapable of truth or falsity [Sider] |
| Full Idea: When a variable is not combined with a quantifier (and so is 'free'), the result is, intuitively, semantically incomplete, and incapable of truth or falsity. | |
| From: Theodore Sider (Logic for Philosophy [2010], 4.2) |
| 9135 | We now see that generalizations use variables rather than abstract entities [Sorensen] |
| Full Idea: As philosophers gradually freed themselves from the assumption that all words are names, ..they realised that generalizations really use variables rather than names of abstract entities. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 8.4) | |
| A reaction: This looks like a key thought in trying to understand abstraction - though I don't think you can shake it off that easily. (For all x)(x-is-a-bird then x-has-wings) seems to require a generalised concept of a bird to give a value to the variable. |
| 12797 | If plural variables have 'some values', then non-count variables have 'some value' [Laycock] |
| Full Idea: If a plural variable is said to have not a single value but some values (some clothes), then a non-count variable may have, more quirkier still, some value (some clothing, for instance) in ranging arbitrarily over the scattered stuff. | |
| From: Henry Laycock (Words without Objects [2006], 4.4) | |
| A reaction: We seem to need the notion of a sample, or an archetype, to fit the bill. I hereby name them 'sample variables'. Damn - Laycock got there first, on p.137. |