a)  What is the principle of verification according to Ayer? What does Ayer mean by “the elimination of metaphysics”? How does the principle of verification support this elimination?
b) In the appendix to LTL, Ayer considers and responds to several objections to hisformulation of he principle of verification. Pick one objection. Explain and evaluate Ayer’s response.

The verifiability principle is a philosophical ideology holding that a statement is meaningful only if it is either empirically verifiable or tautological. In Ayer’s ​Language, Truth, and Logic (LTL)​, he adopts a “modified principle of verification”, to test whether a sentence expresses a genuine empirical hypothesis by requiring that some possible sense-experience be relevant to the determination of its truth or falsehood. With the exception of tautologies, propositio​ns that are true in virtue of the meaning of their terms, if a proposition fails to satisfy this principle, Ayer holds that it must be metaphysical. In being so, he claims that it is then neither true or false, but rather literally senseless. As an empiricist, Ayer believes that propositions which cannot be derived from observations or sense-experiences, such as many non-tautological philosophical propositions, ​ethical, aesthetic, and religious statements are linguistically necessary, and so analytic, but not in fact meaningful​. Such propositions are asserted to be emotionally significant in that they influence feelings and beliefs, but not in virtue of granting any knowledge or having any meaning.

In his first chapter of LTL, “The Elimination of Metaphysics”, he elaborates on the Kantian views of metaphysics, which like Ayer’s, claims that metaphysicians cannot be justified in asserting that things exist beyond ourselves, or in defining the boundaries of human understanding, if it is only possible to know what lies within the bounds of sense-experience. However, he states that the true problem in metaphysics is not that it attempts to overstep an impossible barrier, but rather that it produces sentences which fail to be literally significant. For this reason, he establishes the criterion of verifiability, to test the genuineness of statements. He states that a sentence is factually significant if, and only if, the proposition it claims to express can be verified through observations. That is, observations must lead one to accept the proposition as being true, or reject it as being false. However, if a non-tautological proposition truth or falsehood is determined by an assumption regarding the nature of future experience, it is considered to be a pseudo-proposition, and the sentence expressing it, although emotionally significant, is not literally significant. Similarly, questions that cannot be answered with observations, are not genuine questions despite having strong grammatical foundations. Ayer clarifies that due to the inability to establish with certainty the truth of general propositions of law by any finite series of observations, he chooses to fall back on the “weaker sense of verification”, meaning that instead of demanding observations to be the only determinant of a statement’s truth or falsehood, he deems that they merely be relevant to this determination. A statement then is considered nonsensical if it fails to comply with this standard of relevance. In having created this criterion for verification, Ayer derives that all propositions which have factual content are empirical hypotheses, that provide a rule for the anticipation of experience. In this way, if a statement is not relevant to some actual, or possible experience, it has no factual content and cannot then be considered an empirical hypothesis. For this reason, Ayer claims that metaphysical sentences are nonsensical in that they not only lack factual content, but they are not a priori propositions, all of which are tautologies. Such sentences aim to express genuine propositions but fail to do so as they are neither tautologies or empirical hypotheses. Having determined that, Ayer’s attack on metaphysics is that it unintentionally formulates nonsensical sentences in being deceived by grammar. The principle of verification supports Ayer’s “Elimination of Metaphysics”, that is, his belief that there is no reason for it, in that despite being held to have moral or aesthetic value, it is entirely senseless.

Despite the intent of Ayer’s “revised” principle of verification to offer a criterion to determine whether a sentence has literal meaning based on the analyticity or empirical verifiability of it’s expressed proposition, this principle has suffered some objections which are touched upon in his work’s appendix. The main objection Ayer addresses is that the principle of verification appears to be incomplete as a criterion of meaning because it disregards cases where sentences do not express any propositions. According to the principle, unless a sentence is determined to be literally meaningful, it does not express an analytic or empirically verifiable proposition, and assuming that every proposition has a definite truth value, there would appear to be nothing that the sentence could properly be said to express. Therefore, to say that a meaningless sentence doesn’t express anything, while establishing that what it expresses is empirically unverifiable, is self-contradictory in that it implies that something is being expressed. Ayer states that his way of trying to avoid this difficulty, by speaking of “putative propositions” and propositions which a sentence “purports to express”, is unsatisfactory as it is terminologically unclear. For this reason, he introduces several ways to eliminate this confusion. His prefered solution to the problem however, is with the introduction of the technical term “statement”, whose usage will slightly differ from the traditional one. He proposes that every indicative sentence despite being literally meaningful or not, shall be regarded as expressing a statement, and that any set of mutually translatable sentences will be said to express the same statement. Moreover, he states that sentences will express “propositions” only if they are literally meaningful, making “propositions” a subclass of “statements”. In having established this, Ayer’s revised principle of verification can, in addition to ​testing whether a sentence expresses a genuine empirical hypothesis​, provide a means of determining whether an indicative sentence expresses a proposition, or a mere statement.

Based on: Ayer, A.J. Language, Truth, and Logic, 1936.