The Logical Syntax of Language. By Rudolf Camap. Translated from the German by Amcthc Smcaton. New York: Harcourt, Brace and Company. $7.50. Language, Truth and Logic. By Alfred J. Ayer. New York: Oxford University Press. $3.00.
Traditional systems of philosophy may roughly be classified as “metaphysical” and “empirical.” Suppose that we regarded a given philosophical system as a series of statements. These statements, we should discover, are not all of the same kind. Some are assertions about the characteristics of “reality,” others are statements of everyday fact, still others statements of the author’s aim. Statements of the first kind are usually considered to be the most important, and so we may ask, how are we to go about finding evidence that they are true or false? This question could not be answered satisfactorily if, for instance, it were asked concerning “The Absolute is self-conscious.” We may call this a metaphysical statement. And we may speak of a philosophical system in which such statements predominate as a metaphysical system. Systems, on the other hand, which at least in intention exclude such statements we may call empirical.
It was in a spirit of rebellion against metaphysics that the movement known as scientific empiricism (formerly “logical positivism”) originated. In the early nineteen-twenties a group including Professor Carnap met periodically in Vienna and was called, as it still is, the Vienna Circle. A steadily growing literature emerging from its discussions has resulted in the gradually improved formulation of the early views, and in the writings of Carnap scientific empiricism attains a high degree of precision. But it must not be imagined that the purpose of the Vienna Circle rested with a critique of metaphysics, for this would have meant only the refinement of arguments already advanced by Hume and Comte. The rejection of metaphysics entails the rejection of virtually all traditional philosophy, and it is not easy to convince traditional philosophers that they lack a subject-matter. It has therefore devolved upon scientific empiricism to redefine the function of philosophy. The reasons why this redefinition was necessary are given in Mr. Alfred J. Ayer’s “Language, Truth and Logic”; the difficult task of preparing the ground for the practice of philosophy as redefined is undertaken by Professor Carnap in “The Logical Syntax of Language.”
It is impossible here to do more than mention four points of general interest in scientific empiricism and thereby perhaps indicate its significance. The first point is discussed by Mr. Ayer; the other three are discussed in “The Logical Syntax of Language,” primarily in Part V.
1. In order that a statement of fact should be meaningful, it must be possible to make observations which will enable us to ascertain (not “ascertain conclusively”) the statement’s truth or falsity. We can specify, if not actually carry out, the observations by which we gather evidence for the truth or falsity of scientific laws, and we can specify what observations will help establish the truth of ordinary common-sense statements; hence these are meaningful. But a metaphysical statement is meaningless, because it is not possible to collect evidence for it: we cannot say what the observable difference would be if it were true or false. Similarly, the problems which metaphysical statements attempt to answer are pseudo-problems. If “Spirit is the sole reality” and “Matter is the sole reality” are answers to a problem, what would the observable difference be if one or the other were true?
2. There are two domains of inquiry by means of which theoretical knowledge is increased. One comprises the individual sciences, such as physics, biology, and history. The other consists in the logical analysis of these sciences. The sciences alone can make statements about the actual world and its characteristics. It is the business of logical analysis (or logical syntax) to examine the nature of science as a whole, the manner in which scientific laws are expressed, the differences between the laws of one science and another, and the general relationship of the various sciences.
3. The way in which logical analysis deals with the various sciences as its subject-matter is to regard them as language-systems. Its function is to deal not only with the languages called the sciences but with any language whatsoever. What, after all, is a language? It consists, first, of symbols, for example, words; but it requires also certain rules, and these are of two kinds. One states how the symbols may be combined to form sentences; the second states how we can deduce some sentences from others, or under what conditions one sentence is to mean the same thing as another. An example of the second kind of rule would be the one stating that “All men are mortal” is to mean the same as “No men are immortal.” Now these two sets of rides constitute the logic of the language. The distinction between the language and the logic of the language is important. For the logic is itself a language whose subject-matter is the language of which it is the logic. Thus, for instance, while the subject-matter of physics is the physical world, the subject-matter of the logic of physics is the terms and sentences in which physics is expressed. So that the logical syntax, or logic, of physics consists of statements about the statements of physics. Let us call the statements of a language “object-sentences,” and the statements of the logic of a language “syntactical sentences.” The object-sentences of some languages, for example, physics, are statements of fact; those of other languages, for example, mathematics, are not. We may consider metaphysical statements as object-sentences of a certain language which, though it purports to make statements of fact, fails to meet the requirements of a language which actually does so. While metaphysical statements constitute the bulk of traditional philosophy, there are certain philosophical statements which seem to be factual sentences but are syntactical sentences in disguise. For example, traditional philosophy says, “That A should be taller than B, and B taller than A, is an impossible state of affairs”; but logical syntax expresses it this way: ” ‘A is taller than B, and B is taller than A’ is a contradictory sentence.” For the statement is really about another statement, not about a fact.
4. The function of philosophy is the logical analysis of language. The charge that philosophy as thus conceived is a barren investigation would not have been without justice, say, a generation ago. Only recently has logic been liberated from its narrow traditional status, though its great renascence dates from the middle of the last century. Professor Carnap, building on this foundation, has created a solid framework of logical concepts. He intends it as the proper instrument of philosophy, which in true scientific fashion will replace private speculation by co-operative and self-corrective inquiry, and which will no longer wallow in a universal ferment of controversy.
Mr. Ayer, who acknowledges his debt to Professor Car-nap, shows, among other things, how logical analysis may be fruitfully applied to the vast, unsystematized domain known as the language of everyday life, and how its function is to clarify the rules governing that language. Professor Carnap’s remarkable book, largely concerned with technical matters and replete with symbolism, will be rough going for philosophers who have neglected the study of modern logic. Carnap has, however, published an excellent little book called “Philosophy and Logical Syntax” which will serve as an introduction to the present one and supplement Mr. Ayer’s volume as a survey of scientific empiricism in general.
Philosophy, like politics, has its conservatives, and scientific empiricism has met stubborn opposition. Much the noisiest has come from those whose understanding of its principal theses is imperfect. There is a sounder group of critics who are in general agreement with scientific empiricism and who, together with its nominal proponents, are the guarantors of its future.