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[2. The Main Philosophical Tenets of Logical Positivism.]

b. Elimination of Metaphysics.

The attitude of logical positivism towards metaphysics is well expressed by Carnap in the article Überwindung der Metaphysik durch Logische Analyse der Sprache in Erkenntnis, vol. 2, 1932 (English translation The Elimination of Metaphysics Through Logical Analysis of Language.) A language − says Carnap − consists of a vocabulary, i.e. a set of meaningful words, and a syntax, i.e. a set of rules governing the formation of sentences from the words of the vocabulary. Pseudo-statements, i.e. sequences of words that at first sight resemble statements but in reality have no meaning, are formed in two ways: either meaningless words occur in them, or they are formed in an invalid syntactical way. According to Carnap, pseudo-statements of both kinds occur in metaphysics.

A word W has a meaning if two conditions are satisfied. First, the mode of the occurrence of W in its elementary sentence form (i.e. the simplest sentence form in which W is capable of occurring) must be fixed. Second, if W occurs is an elementary sentence S, it is necessary to give an answer to the following questions (that are − according to Carnap − equivalent formulation of the same question):

(1.) What sentences is S deducible from, and what sentences are deducible from S?
(2.) Under what conditions is S supposed to be true, and under what conditions false?
(3.) How S is to verified?
(4.) What is the meaning of S?
(R. Carnap, The Elimination of Metaphysics Through Logical Analysis of Language in Sarkar, Sahotra (ed.), Logical Empiricism at its Peak: Schlick, Carnap, and Neurath, New York: Garland Pub., 1996, p. 12)

An example offered by Carnap concerns the word "arthropode". The sentence form "the thing x is an arthropode" is an elementary sentence form that is derivable from "x is an animal", "x has a segmented body" and "x has jointed legs". Conversely, these sentences are derivable from "the thing x is an arthropode". Thus the meaning of the words "arthropode" is determined.

According to Carnap, many words of metaphysics do not fulfil these requirements and thus they are meaningless. As an example, Carnap considers the word "principle". This word has a definite meaning, if the sentence "x is the principle of y" is supposed to be equivalent to the sentences "y exists by virtue of x" or "y arises out of x". The latter sentence is perfectly clear: y arises out of x when x is invariably followed by y, and the invariable association between x and y is empirically verifiable. But − says Carnap − metaphysicians are not satisfied with this interpretation of the meaning of "principle". They assert that no empirical relations between x and y can completely explain the meaning of "x is the principle of y", because there is something that cannot be grasped by means of the experience, something for which no empirical criterion can be specified. It is the lacking of any empirical criterion − says Carnap − that deprives of meaning the word "principle" when it occurs in metaphysics. Metaphysical pseudo-statements such as "water is the principle of the world" or "the spirit is the principle of the world" are void of meaning because a meaningless word occurs in them.

There are also pseudo-statements that consist of meaningful words. An example is the word sequence "Caesar is a prime number" that has the same form of "Caesar is a general". These two sentences are well formed in English, because there is not a grammatical distinction between predicates which can be affirmed of human beings (such as "general") and predicates which can be affirmed of numbers (such as "prime number"). Although every word occurring in "Caesar is a prime number" has a definite meaning, the sequence evidently has no meaning. In a logically constructed language - says Carnap - a distinction between the different kinds of predicates is specified, and pseudo-statements as "Caesar is a prime number" could not arise. Metaphysical statements which do not contain meaningless words are indeed meaningless because they are formed in a way which is admissible in natural languages but not admissible in logically constructed languages.

What are the most frequent sources of errors from which metaphysical pseudo-statements arise? A source of mistakes is the ambiguity of the verb "to be", which is sometimes used as a copula ("I am hungry") and sometimes to designate existence ("I am"). The latter statement incorrectly suggests a predicative form, and thus it suggests that existence is a predicate. Modern logic has introduced an explicit sign to designate existence (the sign ), which occurs only in statements such as xP(x). Therefore modern logic has clarified that existence is not a predicate, and has revealed the logical error from which pseudo-statements such as "cogito, ergo sum" arose. Another source of mistakes is type confusion, in which a predicate is used as predicate of a different type (see the example "Caesar is a prime number").

What is the role of metaphysics? According to Carnap, although metaphysics has not theoretical content, it has a content indeed: metaphysical pseudo-statements express the attitude of a person towards life. The metaphysician, instead of using the medium of art, works with the medium of the theoretical; he confuses art with science, attitude towards life with knowledge, and thus produces an unsatisfactory and inadequate work. "Metaphysicians are musicians without musical ability" (Carnap, The Elimination of Metaphysics, in Sarkar, Sahotra (ed.), Logical Empiricism at its Peak, p. 30).

Verifiability Principle

The Language of Science