Language, Truth and Logic

Criterion of Truth?

In terms of modern philosophers, Alfred Jules Ayer is undeniably among the most famous for his Americanized interpretation of logical positivism expressed within his work Language Truth and Logic. Ayer’s initial endeavor within Chapter I is best expressed in it’s title: “The Elimination of Metaphysics”. His goal is to refute “the metaphysical thesis that philosophy affords us knowledge of a reality transcending the world of science and common sense” (33). In order to do this Ayer tactfully chooses to go after the sentence structure of metaphysical statements rather than their meanings. The method which he uses to analyze these sentences is referred to as the “criterion of verifiability”, which can be applied to the ideas of Plato.

The criterion of verifiability is stated as follows: “A sentence is factually significant to any person if they know how to verify the proposition which it purports to express – that is, if they know what observation would lead them under certain conditions to accept the proposition as true or reject it as being false” (35). The “observations” which Ayer alludes to are those obtained through the senses alone. If no such sense-based annotations were used in either verifying or refuting the statement presented it therefore has no relevance and is considered nonsense. If it can, in fact, be verified, then it must be either empirically or tautologically based. Tautological statements, also known as conceptual truths, are those which are always truthful in virtue of meaning. The proof for tautology is inherent within the fact that it must contain truth’s based on fact rather than experience. In order for a statement to meet the requirements of an empirical verification it doesn’t necessarily have to be true, in fact if it can be empirically proved to be false it still remains a verified declaration. What it must have, however, is either practical or principle verifiability, meaning that it must be in some way verifiable through the senses, or at least theoretically conceivable through them. In further pursuit of precisely defining the terms within the criterion of verifiability, Ayer defines empirical verification as either strong or weak, stating, “A proposition is said to be verifiable, in the strong sense of the term, if, and only if, its truth could be conclusively established in experience. But it is verifiable, in the weak sense, if it is possible for experience to render it probable” (37). A dilemma that arises within such a statement is that nothing is completely verifiable, making experience render every proposition only probable rather than conclusive. “If it is recognized that such general propositions of law are designed to cover an infinite number of cases, then it must be admitted that they cannot, even in principle, be verified conclusively” (37). What these refutations inevitably lead us to is the classification of all verifications as weak, but with a simple question surrounding it, “would any observations be relevant to the determination of the putative statement’s truth or falsehood? And it is only if a negative answer is given to this question that we conclude that the statement under consideration is nonsensical” (38). In this sense, whether a statement has a strong or weak verification aspect is irrelevant, it is only whether it is verifiable at all. Ayer’s system of verifiability, now established, can be used to analyze the statements of metaphysicians.

“No statement which refers to a ‘reality’ transcending the limits of all possible sense-experience can possibly have any significance” (38). Ayer’s arguments seem to be directed specifically at criticizing metaphysical works as being unnecessary within the world of philosophy. In looking at Plato’s Dialogs two prevalent statements arise which we can here further analyze. The first concerns the “transcendent realm of Forms” in which Plato claims there exists a world separate of our senses containing all the attributes of the objects we see. If we are to make a simple statement in order to be analyzed by the criterion of verifiability, it might look something like, “a Transcendent Realm of Forms exists”. Immediately one can see that the statement is going to have trouble passing as verifiable according to the criterion established. The statement is not tautological due to its lack of conceptual truth. Empirically, it may be argued that all senses are deceiving and therefore the Realm may exist just beyond what we can perceive as a conceptual verification. Ayer refutes this through the following argumentation, “the senses sometimes deceive us, just because the expectations to which our sense-experiences give rise do not always accord what we subsequently experience…therefore the fact that our perceptual judgments are sometimes found to be erroneous has not the slightest tendency to show that the world of sense-experience is unreal… Consequently, anyone who condemns the sensible world as a world of mere appearance, as opposed to reality, is saying something which, according to our criterion of significance, is literally nonsensical” (39). By first refuting that the senses are deceitful based on the fact that the senses themselves are what deceive us, Ayer then claims that if a transcendent world exists it cannot even be an empirical truth because it cannot be either practically or theoretically verified through the senses. The second statement which Plato asserts in his Dialogs is that “all souls are immortal”. Again, tautological verification shows that the statement is not a priori but rather a posteriori, because you would have to experience it as being true, if at all. One does not simply know, without any prior experience, that a soul can exist, let alone be immortal. And once more we are left with determining whether the existence of immortal souls is empirically verifiable. If the proposition were to be verifiable in principle it would have to be theoretically conceivable through observation made through the senses. However, the senses cannot perceive the notion of a soul, let alone contemplate it’s existence. Because the soul cannot be conceived through the observations allowed within the criterion it is considered a pseudo-proposition. And while it may hold emotional or spiritual significance to some, it ultimately “fails to conform to the conditions under which alone a sentence can be literally significant” (35).

Although it may seem that Ayer is rejecting the significance of all metaphysical statements through failing to verify them under the criterion of verifiability, it is clear that he simply does not want them to be considered within the field of philosophy. “there remain a number of metaphysical passages which are the work of genuine mystical feeling; and they may more plausibly be held to have moral or aesthetic value. But, as far as we are concerned, the distinction between the kind of metaphysics that is produced by a philosopher who has been duped by grammar, and the kind that is produced by a mystic who is trying to express the inexpressible, is of no great importance” (45). Ayer calls instead for a distinction to be made between philosophy and metaphysics with evidence that truly philosophical questions are verifiable whereas metaphysical ones are nonsensical.