CHAPTER ONE
FREGE
Michael Beaney
Gottlob Frege (1848â1925) was primarily a mathematician, logician and philosopher of mathematics rather than a philosopher of language as that might be understood today. However, in inventing modern logic and pursuing his main goal â the demonstration that arithmetic can be reduced to logic â he was led to reflect on how language works, and the ideas he introduced in doing so laid the foundations for the development of philosophy of language, especially within the analytic tradition, in the twentieth century.
1. Life and works
Frege was born in Wismar, on the Baltic coast in northern Germany, in 1848, and he studied mathematics, physics, chemistry and philosophy at the Universities of Jena and Göttingen from 1869 to 1873. In 1874 he was appointed to teach mathematics at Jena, where he remained for the rest of his academic career. He retired in 1918 and moved back to the Baltic coast, where he died in 1925.1
Frege published three books in his lifetime: Begriffsschrift (Conceptual Notation) in 1879, Die Grundlagen der Arithmetik (The Foundations of Arithmetic) in 1884 and Grundgesetze der Arithmetik (Basic Laws of Arithmetic) in 1893 (Volume I) and 1903 (Volume II). Fregeâs main aim in these books was to demonstrate the logicist thesis that arithmetic is reducible to logic. To do so, Frege realized that he needed to develop a better logical theory than was then available: he gave his first exposition of this in Begriffsschrift, âBegriffsschriftâ (literally, âconcept-scriptâ or âconceptual notationâ) being the name he gave to his logical system. (In what follows, I shall use âBegriffsschriftâ in italics to refer to the book and without italics to refer to Fregeâs logical system.) In Grundlagen he criticized other views about arithmetic, such as those of Kant and Mill, and offered an informal account of his logicist project. In Grundgesetze he refined his logical system and attempted to provide a formal demonstration of his logicist thesis. In 1902, however, as the second volume was in press, he received a letter from Russell informing him of a contradiction in his system â the contradiction we know now as Russellâs paradox. Although Frege hastily wrote an appendix attempting to respond to this, he soon realized that the response failed and was led to abandon his logicism. He continued to develop and defend his philosophical ideas, however, writing papers and corresponding with other mathematicians and philosophers. It is these philosophical writings, and his four most important papers, in particular, which have established his status as one of the founders of modern philosophy of language. These papers are âFunction and Conceptâ (1891), âOn Sense and Referenceâ (1892a), âOn Concept and Objectâ (1892b) and âThoughtâ (1918). The main ideas in these four papers form the subject of the present chapter. We start with the idea that lay at the heart of his new logical system.
2. Fregeâs use of functionâargument analysis
The key to understanding Fregeâs work is his use of functionâargument analysis, which he extended from mathematics to logic. Indeed, it is no exaggeration to say that all Fregeâs main doctrines follow from his thinking through the implications of this use.2 We can begin with a simple example from mathematics. In analytic geometry, the equation for a line is y = ax + b: this exhibits y as a function of x, with a and b here being constants (a being the gradient of the line and b the point where the line cuts the y-axis on a graph). Let a = 2 and b = 3. If x = 4, then y = 11: we say that 11 is the value of the function 2x + 3 for argument 4. We call x and y the variables here: as x varies, so too does y, in the systematic way reflected in the function. By taking different numerical values for x, we get different numerical values for y, enabling us to draw the relevant line on a graph. Frege thought of sentences â and what those sentences express or represent â in the same way: they can be analysed in functionâargument terms. Sentences, too, have a âvalueâ which can be seen as the result of an appropriate function for an appropriate argument or arguments. If we think of this value as in some sense its âmeaningâ, then we can regard this meaning, too, as a function of the âmeaningsâ of what we might loosely call its âpartsâ, that is, of what functionâargument analysis yields as the constituent elements of the sentence. What are these âmeaningsâ and âpartsâ? This is the question that Frege attempted to answer in his philosophical work, and it is the main aim of the present chapter to explain his answer.
Let us see how Frege applied functionâargument analysis in the case of sentences, starting with simple sentences such as âGottlob is humanâ. In traditional (Aristotelian) logic, such sentences were regarded as having subjectâpredicate form, represented by âS is Pâ, with âSâ symbolizing the subject (âGottlobâ) and âPâ the predicate (âhumanâ), joined together by the copula (âisâ). According to Frege, however, they should be seen as having functionâargument form, represented by âFaâ, with âaâ symbolizing the argument (âGottlobâ) and âFxâ the function (âx is humanâ), the variable x here indicating where the argument term goes to complete the sentence. The sentence âGottlob is humanâ is thus viewed as the value of the functional expression âx is humanâ for the argument term âGottlobâ. Besides the terminological change, though, there might seem little to choose between the two analyses, the only difference being the absorption of the copula (âisâ) into the functional expression (âx is humanâ).3
The advantages of functionâargument analysis begin to emerge when we consider relational sentences, which are analysed as functions of two or more arguments. In âGottlob is shorter than Bertrandâ, for example, âGottlobâ and âBertrandâ are taken as the argument terms and âx is shorter than yâ as the relational expression, formalized as âRxyâ or âxRyâ. This allows a unified treatment of a wide range of sentences which traditional logic had had difficulties in dealing with in a single theory.
The superior power of functionâargument analysis only fully comes out, though, when we turn to sentences involving quantifier terms such as âallâ and âsomeâ. Take the sentence âAll logicians are humanâ. In traditional logic, this was also seen as having subjectâpredicate form, âAll logiciansâ in this case being the subject, with âhumanâ once again the predicate, joined together by the plural copula âareâ. According to Frege, however, such a sentence has a quite different and more complex (quantificational) form: in modern notation, symbolized as â(âx)(Lx â Hx)â,4 read as âFor all x, if x is a logician, then x is humanâ. Here there is nothing corresponding to the subject; instead, what we have are two functional expressions (âx is a logicianâ and âx is humanâ) linked together by means of the propositional connective âif ⊠then âŠâ and bound by a quantifier (âfor all xâ). In developing his Begriffsschrift, Fregeâs most significant innovation was the introduction of a notation for quantification, allowing him to formalize â and hence represent the logical relations between â sentences not just with one quantifier term but with multiple quantifier terms.
Traditional logic had had great difficulty in formalizing sentences with more than one quantifier term. Such sentences are prevalent in mathematics, so it was important for Frege to be able to deal with them. Consider, for example, the sentence âEvery natural number has a successorâ. This can be formalized as follows, âNxâ symbolizing âx is a natural numbe...