Verificationism and the Critique of Metaphysics

Not surprisingly, it was the Circle’s rejection of metaphysics by means of their seemingly devastating criterion of cognitive significance that attracted immediate opposition. (That they did not deny all meaning to statements thus ruled out of court was freely admitted from early on, but this “expressive” surplus was considered secondary to so-called “cognitive” meaning and discountable in science (see Carnap 1928b, 1932a).) Notwithstanding the metaphysicans’ thunder, however, the most telling criticisms of the criterion came from within the Circle or broadly sympathetic philosophers. When it was protested that failure to meet an empiricist criterion of significance did not make philosophical statements meaningless, members of the Circle simply asked for an account of what this non-empirical and presumably non-emotive meaning consisted in and typically received no convincing answer. The weakness of their position was rather that their own criterion of empirical significance seemed to resist an acceptable formal characterization.
To start with, it must be noted that long before the verification principle proper entered Circle’s discourse in the late 1920s, the thought expressed by Mach’s dictum that “where neither confirmation nor refutation is possible, science is not concerned” (1883 [1960, 587]) was accepted as a basic precept of critical reflection about science. Responsiveness to evidence for and against a claim was the hallmark of scientific discourse. (Particularly the group Frank-Hahn-Neurath, who formed part of a pre-World War I discussion group (Frank 1941, 1949a) sometimes called the “First Vienna Circle” (Haller 1985, Uebel 2003), can be presumed to be familiar with Mach’s criterion.) Beyond this, still in the 1920s, Schlick (1926) convicted metaphysics for falsely trying to express as logically structured cognition what is but the inexpressible qualitative content of experience. Already then, however, Carnap (1928b, §7) edged towards a formal criterion by requiring empirically significant statements to be such that experiential support for them or for their negation is at least conceivable. Meaningfulness meant the possession of “factual content” which could not, on pain of rendering many scientific hypotheses meaningless, be reduced to actual testability. Instead, the empirical significance of a statement had to be conceived of as possession of the potential to receive direct or indirect experiential support (via deductive or inductive reasoning).
In 1930, considerations of this sort appeared to receive a considerable boost due to Waisman’s reports of Wittgenstein’s meetings with him and Schlick. (Wittgenstein discussed the thesis “The meaning of its sentence is its verification” in conversations with Schlick and Waismann on 22 December 1929 and 2 January 1930 (see Waismann 1967 [1979]). The thesis was elaborated in Waismann’s “Theses” dated to “around 1930” which were presented as Wittgenstein’s considered views.) While Wittgenstein may have thought of this statement more as a constitutive principle of meaning, in the Circle it was put to work primarily as a demarcation criterion against metaphysics. Note that even though this early Wittgensteinian version of the meaning criterion required conclusive verifiability (which Carnap’s of 1928 did not), it also allowed for verifiability in principle only (and did not demand actual verifiability). Like Carnap’s notion of experiential support, this criterion worked with the mere conceivability of verifiability. (The demand for conclusive verifiability was discussed in the meetings with Wittgenstein.) By 1931, however, it had become clear to some that this would not do. What Carnap later called the “liberalization of empiricism” was underway and different camps became discernible within the Circle. It was over this issue that the so-called “left wing” with Carnap, Hahn, Frank and Neurath first distinguished itself from the “more conservative wing” around Schlick. (See Carnap 1936–37, 422 and 1963a, §9. Carnap 1936–37, 37n dated the opposition to strict verificationism to “about 1931”.)
In the first place, this liberalization meant the accommodation of universally quantified statements and the return, as it were, to salient aspects of Carnap’s 1928 conception. Everybody had noted that the Wittgensteinian verificationist criterion rendered universally quantified statements meaningless. Schlick (1931) thus followed Wittgenstein’s own suggestion to treat them instead as representing rules for the formation of verifiable singular statements. (His abandonment of conclusive verifiability is indicated only in Schlick 1936a.) By contrast, Hahn (1933, drawn from lectures in 1932) pointed out that hypotheses should be counted as properly meaningful as well and that the criterion be weakened to allow for less than conclusive verifiability. But other elements played into this liberalization as well. One that began to do so soon was the recognition of the problem of the irreducibility of disposition terms to observation terms (more on this presently). A third element was that disagreement arose as to whether the in-principle verifiability or support turned on what was merely logically possible or on what was nomologically possible, as a matter of physical law etc. A fourth element, finally, was that differences emerged as to whether the criterion of significance was to apply to all languages or whether it was to apply primarily to constructed, formal languages. Schlick retained the focus on logical possibility and natural languages throughout, but Carnap had firmly settled his focus on nomological possibility and constructed languages by the mid-thirties. Concerned with natural language, Schlick (1932, 1936a) deemed all statements meaningful for which it was logically possible to conceive of a procedure of verification; concerned with constructed languages only, Carnap (1936–37) deemed meaningful only statements for whom it was nomologically possible to conceive of a procedure of confirmation of disconfirmation.
Many of these issues were openly discussed at the Paris congress in 1935. Already in 1932 Carnap had sought to sharpen his previous criterion by stipulating that those statements were meaningful that were syntactically well-formed and whose non-logical terms were reducible to terms occurring in the basic observational evidence statements of science. While Carnap’s focus on the reduction of descriptive terms allows for the conclusive verification of some statements, it must be noted that his criterion also allowed universally quantified statements to be meaningful, provided they were syntactically and terminologically correct (1932a, §2). It was not until one of his Paris addresses, however, that Carnap officially declared the meaning criterion to be mere confirmability. Carnap’s new criterion required neither verification nor falsification but only partial testability so as now to include not only universal statements but also the disposition statements of science (see Carnap 1936–37; the English translation of the original Paris address (1936a [1949]) combines it with extraneous material). These disposition terms were thought to be linked to observation statements by a variety of reduction postulates or longer reduction chains, all of which provided only partial definitions (despite their name they provided no eliminative reductions). Though plausible initially, the device of introducing non-observational terms in this way gave rise to a number of difficulties which impugned the supposedly clear distinctions between logical and empirical matters and analytic and synthetic statements (Hempel 1951, 1963). Independently, Carnap himself (1939) soon gave up the hope that all theoretical terms of science could be related to an observational base by such reduction chains. This admission raised a serious problem for the formulation of a meaning criterion: how was one to rule out unwanted metaphysical claims while admitting as significant highly abstract scientific claims?
Consider that Carnap (1939, 1956b) admitted as legitimate theoretical terms that may be merely implicitly defined in calculi that are themselves only partially interpreted by correspondence rules between some select calculus terms and expressions belonging to an observational language (via non-eliminative reductions). The problem was that mere confirmability was simply too weak a meaning criterion to rule out some putative metaphysical claims. Moreover, this problem arose for both the statement-based approach to the criterion (taken by Carnap in 1928, by Wittgenstein in 1929/30, and by Ayer both in the first (1936) and the second editions (1946) of Language Truth and Logic) and for the term-based approach (taken by Carnap since 1932). For the former approach, the problem was that the empirical legitimacy of statements obtained via indirect testing also transferred to any expressions that could be truth-functionally conjoined to them (for instance, by the rule of ‘or’-introduction). Statements thus became empirically significant, however vacuous they had been on their own. For the term-based approach, the problem was that, given the non-eliminability of dispositional and theoretical terms, empirical significance was no longer ascribable to individual expressions in isolation but became a holistic affair, with little guarantee in turn for the empiricist legitimacy of all the terms now involved.
For most critics (even within the ranks of logical empiricism), the problem of ruling out metaphysical statements while retaining the terms of high theory remained unsolved. By 1950, in response to the troubles of Ayer’s two attempts to account for the indirect testing of theoretical statements via their consequences, Hempel conceded that it was “useless to continue to search for an adequate criterion of testability in terms of deductive relationships to observation sentences” (1950 [1959, 116]). The following year, Hempel also abandoned the idea of using, as a criterion of empirical significance, Carnap’s method of translatability into an antecedently determined empirical language consisting only of observational non-logical vocabulary. Precisely because it was suitably liberalized to allow abstract scientific theories with merely partial interpretations, its anti-metaphysical edge was blunted: it allowed for combination with “some set of metaphysical propositions, even if the latter have no empirical interpretation at all” (1951, 70). Hempel drew the holistic conclusion that the units of empirical significance were entire theories and that the measure of empirical significance itself was multi-criterial and, moreover, allowed for degrees of significance. To many, this amounted to the demise of the Circle’s anti-metaphysical campaign. By contrast, Feigl’s reaction (1956) was to reduce the ambition of the criterion of significance to the mere provision of necessary conditions.
Some further work was undertaken on rescuing and, again, debunking a version of the statement-based criterion, but not by (former) members of the Vienna Circle. However, in response to the problem of how to formulate a meaning criterion that suitably distinguished between empirically significant and insignificant non-observational terms, Carnap proposed a new solution in 1956 and another one in 1966. We will return to discuss these separately (see section 3.5 below); for now we need only note that these proposals were highly technical and applied only to axiomatized theories in formal languages. They too, however, found not much favor amongst philosophers. Yet whatever the problems that may or may not beset them, it would seem that far more general philosophical considerations contributed to the disappearance of the problem of meaning criterion from most philosophical discussions since the early 1960s (other than as an example of mistaken positivism). These include the increasing opposition to the distinctions between analytic and synthetic statements and observational and theoretical terms as well as a general sense of dissatisfaction with Carnap’s approach to philosophy which began to seem both too formalist in execution and too deflationary in ambition. The entire philosophical program of which the search for a precise criterion of empirical significance was a part had begun to fall out of favor (and with it technical discussions about the criterion’s latest version).
The widely perceived collapse of the classical Viennese project to find in an empiricist meaning criterion a demarcation criterion against metaphysics—we reserve judgement about Carnap’s last two proposals here—can be interpreted in a variety of ways. It strongly suggests that cognitive significance cannot be reduced to what is directly observable, whether that be interpreted in phenomenalist or intersubjective, physicalist terms. In that important but somewhat subsidiary sense, the collapse spelt the failure of many of the reductivist projects typically ascribed to Viennese neopositivism (but see section 3.3 below). Beyond that, what actually had failed was the attempt to characterize for natural languages the class of cognitively significant propositions by recursive definitions in purely logical terms, either by relations of deducibility or translatability. What failed, in other words, was the attempt to apply a general conception of philosophical analysis as purely formal, pursued also in other areas, to the problem of characterizing meaningfulness.
This general conception can be considered formalist in several senses. It was formalist, first, in demanding the analysis of the meaning of concepts and propositions in terms of logically necessary and sufficient conditions: it was precise and brooked no exceptions. And it was formalist, second, in demanding that such analyses be given solely in terms of the logical relations of these concepts and propositions to other concepts and propositions: it used the tools of formal logic. There is also a third sense that is, however, applicable predominantly to the philosophical project in Carnap’s hands, in that it was formalist since it concentrated on the analysis of contested concepts via their explication in formal languages. (Discussion of its viability must be deferred until sections 3.5 and 3.6 below, since what’s at issue currently is only the formalist project as applied to concepts in natural language.) The question arises whether all Vienna Circle philosophers concerned with empirical significance in natural language were equally affected, for the collapse of the formalist project may leave as yet untouched other ways of sustaining the objection that metaphysics is, in some relevant sense, cognitively insignificant. (Such philosophers in turn would have to answer the charge, of course, that only the formalist project of showing metaphysics strictly meaningless rendered the Viennese anti-metaphysics distinctive.)
Even though the formalist project became identified with mainstream logical empiricism generally (consider its prominence in confirmation theory and in the theory of explanation), it was not universally subscribed to in the Vienna Circle itself. In different ways, neither Schlick nor Neurath or Frank adhered to it. As noted in the overview above, Schlick’s attempts to exhibit natural language meaning abjured efforts to characterize it in explicitly formal terms, even though he accepted the demand for necessary and sufficient conditions of significance. In the end, moreover, Schlick turned away from his colleagues’ search for a criterion of empirical significance. In allowing talk of life after death as meaningful (1936a), for the very reason that what speaks against it is only the empirical impossibility of verifying such talk, Schlick’s final criterion clearly left empiricist strictures behind.
By contrast, Neurath and Frank kept their focus on empirical significance. While they rarely discussed these matters explicitly, their writings give the impression that Neurath and Frank chose to adopt (if not retain) a contextual, exemplar-based approach to characterizing the criterion of meaninglessness and so decided to forego the enumeration of necessary and sufficient conditions. Mach’s precept cited earlier is an example of such a pragmatic approach, as is, it should be noted, Peirce’s criterion of significance, endorsed by Quine (1969), which claims that significance consists in making a discernible difference whether a proposition is likely to be true or false. Mach’s pragmatic approach had been championed already before verificationism proper by Neurath, Frank and Hahn who became, like Carnap, early opponents of conclusive verifiability. (Indeed, it is doubtful whether Neurath’s radical fallibilism, most clearly expressed already in 1913, ever wavered.) This pragmatic understanding found clear expression in Neurath’s adoption (1935a, 1938) of K. Reach’s formulation of metaphysical statements as “isolated” ones, as statements that do not derive from and hold no consequences for those statements that we do accept on the basis of empirical evidence or for logical reasons. (Hempel’s dismissal, in 1951, of this pragmatic indicator presupposes the desiderata of the formalist project.) Finally, there is Frank’s suggestion (1963), coupled with his longstanding advice to combine logical empiricism with pragmatism, that Carnap’s purely logical critique of metaphysics in (1932a) was bound to remain ineffective as long as the actual use of metaphysics remained unexamined. It would be worth investigating whether—if the critique of the alleged reductionist ambitions of their philosophy could also be deflected (see section 3.3 below)—the impetus of the anti-verificationist critique can be absorbed by those with a pragmatic approach to the demarcation against metaphysics. Much as with Quine’s Peirce, such a criterion rules out as without interest for epistemic activity all concepts and propositions whose truth or falsity make no appreciable difference to the sets of concepts and propositions we do accept already.
An entirely different moral was drawn by Reichenbach (1938) and thinkers indebted to his probabilistic conception of meaning and his probabilistic version of verificationism, which escaped the criticisms surveyed above by vagaries of its own. Such theorists perceive the failure of the formalist model to accommodate the empirical significance of theoretical terms to stem from its so-called deductive chauvinism. In place of the exclusive reliance on the hypothetical-deductive method these theorists employ non-demonstrative analogical and causal inductive reasoning to ground theoretical statements empirically. Like Salmon, these theorists adopt a form of “non-linguistic empiricism” which they sharply differentiate from the empiricism of the Vienna Circle (Salmon 1985, 2003 and Parrini 1998).
Now against both the pragmatic and the post-linguistic responses to the perceived failure of the attempt to provide a precise formal criterion of significance serious worries can be raised. Thus it must be asked whether without a precise way of determining when a statement ‘makes an appreciable difference’, criticism of metaphysics based on such a criterion may be not be considered as a biased dismissal rather than a demonstration of fact and so fall short of what is needed. Likewise in the case of the anti-deductivist response, it must be noted that a criterion based on analogical reasoning will only be as effective as the strength of the analogy which can always be criticized as inapt (and similarly for appeals to causal reasoning). The very point of exact philosophy in a scientific spirit—for many the very point of Vienna Circle philosophy itself—seems threatened by such maneuvres. Acquiescence in the perceived failure of the proposed criteria of significance thus comes with a price: if not that of abandoning Vienna Circle philosophy altogether, then at least that of formulating an alternative understanding to how some of its ambitions ought to be understood. (Recent reconstructive work on Carnap, Neurath and Frank may be regarded in this light.)
A still different response—but one emblematic for the philosophical public at large—is that of another of Reichenbach’s former students, Putnam, who has come to reject the anti-metaphysical project that powered verificationism in its entirety. Repeatedly in his later years, Putnam has called for a refashioning of analytic philosophy as such, providing, as it were, a philosophically conservative counterweight to Rorty’s turn to postmodernism. Putnam’s reasons (the alleged self-refutation of the meaning criterion) are still different from those surveyed above and will be discussed when we return to reconsider the very point of the Circle’s campaign against metaphysics (see section 3.6 below).

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Verificationism and the Critique of Metaphysics

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Verificationism and the Critique of Metaphysics

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