Logical positivism was a philosophical movement that began in the 1920s in the Vienna Circle. The philosopher A.J. Ayer (1910-1989) was instrumental in popularizing logical positivism in the English-speaking world. His most famous and systematic exposition and defense of logical positivism was given in his book Language, Truth and Logic. At the heart of logical positivism is the principle of verification (also known as the verification principle, verifiability criterion, principle of verifiability, the verification criterion of meaning, etc.). The principle of verification is a criterion for determining whether or not a sentence is meaningful, where a sentence is meaningful just in case it succeeds in expressing a proposition. A major motivation of the principle is to enable us to distinguish between meaningful statements of logic and natural science and (according to logical positivists) meaningless statements of metaphysics, ethics, theology, and aesthetics. The principle tries to achieve this goal by dividing all propositions into two categories: (1) analytic propositions and (2) empirically verifiable propositions.
Ayer found the historical origin of this bifurcation in the thought of the Scottish Enlightenment philosopher David Hume (1711-1776). In particular, Ayer thought that this bifurcation is precisely the one expressed in Hume's fork, which Hume himself presented as follows:
All the objects of human reason or enquiry may naturally be divided into two kinds, to wit, Relations of Ideas and Matters of Fact. Of the first kind are the sciences of Geometry, Algebra, and Arithmetic; and in short, every affirmation, which is either intuitively or demonstratively certain... Propositions of this kind are discoverable by the mere operation of thought, without dependence on what is any where in the universe...
Matters of fact... are not ascertained in the same manner... That the sun will not rise to-morrow is no less intelligible a proposition, and implies no more contradiction, than the affirmation, that it will rise. We should in vain, therefore, attempt to demonstrate its falsehood (An Enquiry concerning Human Understanding, 4.1-2).
Relations of ideas are analytic, a priori, and necessary. Further, relations of ideas do not affirm (or deny) anything about the world. Ayer understands them as mere tautologies and as bereft of any factual content. Relations of ideas are true (or false) simply in virtue of the meanings of the terms used in the sentences that express them. By contrast, matters of fact are synthetic, a posteriori, and contingent. They affirm (or deny) things about the world and can be known only on the basis of experience. This is reflective of the strong form of empiricism that both Ayer and Hume were committed to. Further, any matter of fact can be affirmed or denied without contradiction, and they are thereby held to be contingent. (This is reflective of the early modern tendency to equate logical consistency with metaphysical possibility).
According to the principle of verification, any sentence that falls outside of these two categories is simply meaningless. In the second edition of Language, Truth and Logic, Ayer explains that his original formulation of the principle (as expressed in the first edition of the book) was as follows:
Principle of Verification 1: A sentence is literally meaningful if and only if the proposition it expresses is either analytic (a relation of ideas) or empirically verifiable (a matter of fact).
In this way, the principle of verification arguably captures what Hume affirmed at the very end of the Enquiry:
If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: For it can contain nothing but sophistry and illusion (An Enquiry concerning Human Understanding, 12.34).
The thesis that Hume was a forerunner of logical positivism is, however, controversial. The principle of verification is a principle about meaning. According to it, any sentence that falls outside of Hume's fork is literally meaningless. It is not clear that this is what Hume affirmed. Some interpreters see Hume as being concerned more with epistemology than with semantics so that if a statement falls outside of Hume's fork, it might very well be perfectly meaningful, but it will nevertheless be such that its truth value is epistemically inaccessible. This exegetical controversy is, however, not the concern of this post. Instead, what I want to focus on is the principle of verification itself and its use by Ayer in arguing that theology is literal nonsense. In particular, I will lay out Ayer's critique of theology based on the principle of verification as well as the various revisions that Ayer applied to the principle of verification in the second edition of Language, Truth and Logic. It will be shown that the principle of verification is hopelessly untenable. Consequently, Ayer's critique of theology, which is based on an application of the principle of verification, is a failure.
Ayer's critique of theology is quite straightforward. He argues that theological statements are neither analytic (i.e., tautological) nor empirically verifiable. Consequently, by the principle of verification, theological statements are literally meaningless. It is important to underscore the radicality of this position. Ayer is not claiming that various theological claims that religious believers hold to are false. Rather, theological claims are meaningless and bear no truth values at all. In this way, Ayer distinguishes his position on the status of theological claims from both atheism and agnosticism as they are traditionally understood (though he would later in life classify himself as an atheist). As Ayer himself explains:
It is important not to confuse this view of religious assertions with the view that is adopted by atheists, or agnostics. For it is characteristic of an agnostic to hold that the existence of a god is a possibility in which there is no good reason either to believe or disbelieve; and it is characteristic of an atheist to hold that it is at least probable that no god exists. And our view that all utterances about the nature of God are nonsensical, so far from being identical with, or even lending any support to, either of these familiar contentions, is actually incompatible with them. For if the assertion that there is a god is nonsensical, then the atheist’s assertion that there is no god is equally nonsensical, since it is only a significant proposition that can be significantly contradicted. As for the agnostic, although he refrains from saying either that there is or that there is not a god, he does not deny that the question whether a transcendent god exists is a genuine question. He does not deny that the two sentences ‘‘There is a transcendent god” and “There is no transcendent god” express propositions one of which is actually true and the other false. All he says is that we have no means of telling which of them is true, and therefore ought not to commit ourselves to either. But we have seen that the sentences in question do not express propositions at all. And this means that agnosticism also is ruled out (Language, Truth and Logic, Ch. VI: "Critique of Ethics and Theology").
Now, one might immediately think that a statement like "God exists" is in fact empirically verifiable. Proponents of the fine-tuning argument (and various design arguments more generally), for instance, certainly hold that there is empirical evidence that increases the likelihood of the existence of God. Consequently, Ayer's argument is unsound even if the principle of verification is true. But this raises the question of what empirical verifiability is supposed to amount to in the first place. This in turn raises issues about how the principle of verification is to be understood and elucidated more generally. It is to this that I turn next. As will be seen, the principle of verification is ultimately untenable.
In the second edition of Language, Truth and Logic, Ayer modifies the principle of verification in a variety of ways in order to escape from various difficulties with the Principle of Verification 1 formulation that he first presents. The first difficulty is that it does not make sense to say that a sentence is meaningless and yet expresses a proposition since a proposition is generally understood as the meaning or information content of a (declarative) sentence. So, in order for a sentence to be meaningful, it must already express a proposition. As such, in order to use the principle as presently formulated, one must first determine whether the sentence that the principle is to be applied to expresses a proposition, but if one has already determined that the sentence in question expresses a proposition, one has thereby already determined that the sentence is meaningful before the principle ever gets applied. Consequently, the principle is otiose. In response to this problem, Ayer introduces a distinction between a sentence and a statement. A sentence is any group of grammatically significant words, and a statement is what is expressed by a declarative sentence, whether that sentence is meaningful or not. A sentence is then meaningful if and only if the statement it expresses is meaningful, a statement is meaningful if and only if it is either analytic or empirically verifiable, and a statement expresses a proposition if and only if the statement is meaningful. The principle of verification can then be reformulated in terms of statements directly rather than in terms of the sentences that express them as follows:
Principle of Verification 2: A statement is literally meaningful if and only if it is either analytic or empirically verifiable.
All of this, however, still leaves the issue of verification unexplained. What does it mean for a statement to be empirically verifiable? First, Ayer distinguishes between weak and strong verification. A statement is strongly verifiable if and only if its truth can be conclusively established in experience, and a statement is weakly verifiable if and only if it is possible for experience to render it probable. Ayer then maintained that only weak verifiability is necessary for the principle of verification to be satisfied. Although Ayer previously did not think that there are any empirical statements that can be strongly verified, he later came to think there are in fact such statements: basic statements. A basic statement is a statement that directly records an immediate sense experience. An example would be the statement "this is white," where this refers ostensively to one's immediate sense experience. Ayer came to allow that such statements are incorrigible in that one cannot be mistaken about their truth (or falsity). (The claim that there are such incorrigible statements has been challenged by some contemporary literature in epistemology, but discussing this is beyond the scope of this post). But in any case, as stated, Ayer only required weak verifiability in order for the principle of verification to be satisfied. To require strong verifiability would unacceptably render many statements of science meaningless as they express mere empirical hypotheses.
Now, Ayer holds that weak verifiability consists in a statement possibly being made probable by experience. In elucidating this, Ayer thinks that experience increases the probability of a statement if the experience is relevant to the truth of the statement. Recognizing the vagueness of this notion of relevance, Ayer introduces the notion of an observation statement and explains relevance in tems of observation statements. An observation statement is a statement that records an actual or possible observation (sense experience). In Humean terms, an observation statement records or refers to a (actual or possible) sense impression (whether simple or complex). Ayer then holds that verifiability in the sense that is strictly required by the principle of verification in order for a statement that is not analytic to be meaningful should be understood as follows: A statement is verifiable just in case an observation statement can be deduced from it in conjunction with certain other premises without being deducible from those other premises alone. This cashes out the way in which an experience is supposed to be relevant to the truth of a statement. In light of this, Ayer introduces the following revised principle of verification:
Principle of Verification 3: A statement is literally meaningful if and only if it is either analytic or if some observation statement can be deduced from it in conjunction with certain other premises without being deducible from those other premises alone.
As Ayer points out, however, the problem with this revision
is that it is far too liberal as it allows any statement whatsoever to be
meaningful. This can be seen as follows: Let “S" be any statement and
let “O" be an observation statement. Then “O" follows from “S" and “if S, then O" without following from “if S, then O”
alone. For example, the statements “the Absolute is lazy” and “if the Absolute
is lazy, then this is white” jointly entail the observation statement “this is
white,” and “this is white” does not follow from either premise taken by itself.
Consequently, “the Absolute is lazy” counts as meaningful, and this is
unacceptable for Ayer. Moreover, since this allows any statement whatsoever to
count as meaningful, this renders the principle of verification worthless.
In response to this problem, Ayer introduces a distinction between direct and indirect verifiability. A statement is directly verifiable if and only if it is either itself an observation statement or is such that in conjunction with one or more observation statements it entails at least one observation statement that is not deducible from these other premises alone. A statement is indirectly verifiable if and only if (i) in conjunction with certain other premises (some of which may be analytic) it entails one or more directly verifiable statements which are not deducible from these other premises alone and (ii) these other premises do not include any statement that is not either analytic, or directly verifiable, or capable of being independently established as indirectly verifiable. This brings us to the final formulation of the principle of verification that Ayer offers in the second edition of Language, Truth and Logic:
Principle of Verification 4: A statement is literally meaningful if and only if it is either analytic or it is either directly or indirectly verifiable.
But even this final formulation of the principle of verification is problematic. For, in the end, it also allows any statement whatsoever to be meaningful. An argument for this fact was given by the mathematical logician Alonzo Church (1903-1995) in his 1949 review of Language, Truth and Logic. The argument is as follows. Let O1, O2, and O3 be any logically independent observation statements, and let S be any statement whatsoever. Then the following statement is directly verifiable:
(α) (~O1 & O2) v (O3 & ~S)
This can be seen as follows. (α) in conjunction with O1 entails O3, and O3 is not deducible from O1 alone (since O1 and O3 are logically independent). Now, either S is indirectly verifiable or ~S is directly verifiable. This can be seen as follows. S and (α) jointly entail O2. Now, either O2 is deducible from (α) alone or it is not. If it is not, then S is indirectly verifiable. If it is, then ~S is directly verifiable since O2 is thereby entailed by O3 & ~S (since (O3 & ~S) entails (α) and (α) entails O2) and O2 is not deducible from O3 alone (since O2 and O3 are logically independent). Thus, either S is indirectly verifiable or ~S is directly verifiable. Consequently, either S is meaningful or ~S is meaningful, and S is meaningful if and only if ~S is meaningful (since meaningfulness is surely closed under logical operations). Therefore, S is meaningful. Since S is any statement whatsoever, it follows that any statement whatsoever is meaningful. Q.E.D.
Thus, the final formulation of the principle of verification that Ayer offers is a failure. The principle of verification is also a failure for an even for fundamental reason: It is self-defeating. For the principle of verification is itself evidently neither analytic nor empirically verifiable. Thus, according to its own standard, the principle of verification is literally meaningless. In the end, then, the principle of verification, particularly with respect to the way in which Ayer formulates it, is untenable. Consequently, Ayer's critique of theology, which crucially relies on the principle of verification, must be deemed a failure.
No comments:
Post a Comment