CRITERIA FOR PLAUSIBLE ARGUMENTS

The most conspicuous datum in philosophy, perhaps the most important one as well, is the following:

(d) Most philosophers consider the thesis of scepticism¹ highly implausible, yet they consider the traditional arguments in its defence highly plausible at first glance.

The rationale for the qualifier ‘at first glance’ in the datum is the following generally accepted thesis concerning plausibility,

(ð) A thesis defensible by plausible arguments is plausible, and vice versa.

Most philosophers would accept our plausibility thesis (p) as a matter of course, if not as analytic. Hence, our datum (d) without the qualifier ‘at first glance’ would allow us to charge most philosophers with inconsis­tency.

(ñ) Most philosophers are inconsistent in viewing scepticism as both implausible and plausible.

The charge is answered, of course, by the qualifier which will force us or modify (c) by qualifying ‘plausible’ in it with ‘seeming’, and this qualifying ‘inconsistent’ likewise.

The outcome, then, would be:

(c') Most philosophers are seemingly inconsistent in viewing scepticism as both implausible and seemingly plausible.

Now, this raises a serious problem. Suppose a philosopher rejects a thesis as implausible. Suppose a colleague advances some plausible argu­ments in its defence. By our plausibility thesis (p) he will consequently have to change his mind. Suppose he is unwilling to do so. Suppose he is unable to do so since his intuitions are too strongly bent on his own views which are contrary to the thesis just proven plausible. Suppose he has suspicions that not all is as clear as he wished. Suppose even that he cannot convince himself on the strength of one or two plausible arguments that practically all his colleagues and illustrious predecessors were utterly in error. What then?

The problem is rather significant.

Lest the reader think that the dilemma just presented is an abstract thought-experiment with little or no practical significance for sane thin­kers, let me mention an example. The details of the example are given in my Faraday as a Natural Philosopher (Chicago University Press, 1971). Rightly or not, I have presented in that book the following story. In the mid-nineteenth century Newtonian mechanics was considered absolutely proven. Some thinkers even said it could never be explained by another theory; all thinkers agreed that it was absolutely true and definitely neither a mere approximation to, nor a special case of, another theory. At that time Faraday strove towards developing another theory of just these qualities. He advanced arguments which he found amply plausible. His contemporaries ignored his theory; even those who admitted some of his arguments in favour of his theory ignored it. In order to compensate him for this disregard of his theory, his comtemporaries rewarded him and praised him all the more for his numerous empirical discoveries (which he made as, and while searching for, plausible arguments for his theory).

Not all manifestations of this dilemma are equally dramatic, of course. As it will soon transpire, the dilemma cannot be very dramatic unless it concerns a very far-reaching thesis. Hence, Faraday’s case is very far from the average, a very extreme case indeed. In principle, however, the dilemma is very common and was implicitly recognized by Francis Bacon who blamed some people for too much self-trust, others for too little self­trust, some for too much dependence on public opinion, others for too much willingness to oppose public opinion. What, however, is the just measure of self trust and of consideration for serious public opinion? At least Faraday tried hard to find the answer to this question, yet he failed. At times, it seems, Bacon and the whole tradition of the Enlightenment, as well as Faraday, recommended the utter disregard for all public opinion. But no one except perhaps Spinoza could live by this standard.

One may, perhaps, sympathize with the problem but declare it no longer pressing in view of the fact that we have now a long and stable tradition of scientific public opinion which one may safely rely upon without becom­ing a dogmatist. This, however, will not do. Unusual as Faraday’s case may have been, it nonetheless refutes (should I say ‘seemingly’?) the view that public opinion, when scientific, can be relied upon. It even refutes the weaker view, which is offered in the preface to the first edition of Popper’s Logik der Forschung, of 1935, and which permits the reliance on scientific public opinion regarding its own problems. ‘A scientist... can attack his problem straight away... For a structure of scientific doctrines is already in existence; and with it, a generally accepted problem­situation....

The gist of all this is to lend force to the problem at hand: when is it forbidden, when is it permissible, when is it imperative, for a member of a learned society, to declare a thesis plausibly defended? (The prohibition and the compulsion may be on the pain of expulsion from the society or of demotion within it; a point noted repeatedly and systematically by Michael Polanyi.) What are our criteria of plausibility? When may (should) we charge one (person or society) with an inconsistency of the type of (c), and when do we have to accept the plea that the inconsistency is only a seeming one of the type of (c')? When is it the case that scepticism is defended by only seemingly plausible arguments and under what con­ditions will scepticism win?

The problem, as my story of Faraday indicates, is not peculiar to philosophy alone. As many other stories, some of them quite well-known, clearly suggest, the same problem occurs in daily life, in political life, in technology, and even in science. (The story of Columbus is so interesting as it is a mixture of all these.) The problem when a thesis is plausibly defended, is all too common. It can be split two ways:

(PA) When is an argument plausible, when is it only seemingly so (as yet)?

(PT) When is a thesis sufficiently defended by admittedly plausible arguments to count as plausible?

To be more precise, the splitting should not be considered a separation, since under certain circumstances a thesis rendered plausible may lend plausibility to some of its more doubtful supporting arguments.

(p) A thesis defensible by plausible arguments is plausible, and vice versa.

Most philosophers of science will want to modify (p) quantitatively. Ignoring the problem (PA) as hardly troublesome, and taking all and only attested relevant facts to constitute plausible (inductive) arguments, they would present a rule for determining numerically the degree of plausible inductive support which given arguments afford a given thesis. They will then add the following rule:

(PIS) A thesis more supportable by plausible inductive arguments than any competing thesis, is the one to be endorsed as scien­tifically plausible.

Even while taking the outlandish view that (PA) does not cause us any trouble, and even while taking the more outlandish view that we can deter­mine quantitatively degrees of inductive support, even then we may still find (PIS) too vague, and for the following reasons. First, it speaks only of support, not of undermining, whereas, at least to begin with, many scientific theories (even well-supported ones) look seriously undermined by known evidence. This perhaps can be remedied by setting-off support against undermining (=negative support). But we know that the initial undermining may be taken lightly at first, and so it is quite different from the undermining which cannot as yet be removed despite certain efforts. Secondly, (PIS) does not say what makes two theses competitors. (The intuitive idea is that two theories are competing if and only if they are contraries, i.e. inconsistent unless referring to non-existent entities. The proviso, however, does not stay unproblematic and the range of contrari­ness can thus easily be expanded indefinitely - which is absurd. This prob­lem is still unstudied, strange to notice.) Nor does (PIS) say what is the set of competing theses - all the known competitors or all the possible ones.

There is one further reason which, I think, invalidates (PIS) as well as all its traditional substitutes. It is this: even if it is at times valid, it must be qualified by additional criteria.

To show this let us follow the suggestion that we should take inadequacy before taking adequacy (a suggestion which Plato’s early dialogues made a central part of our tradition). All existing theories of science consider only one kind of inadequacy, namely poor agreement between theory and fact. This is clearly not sufficient because, as the first reason above indi­cates, some such poor agreements are considered merely temporary set­backs, others not. Hence, there is need for some deeper criterion of in­adequacy. Nor is the temporariness merely a matter of how long and how hard we have already attempted to overcome it. For it may indeed be the case that a theory is engaging us in other directions than the setback, or that the theory pleases us so much with its many agreements with facts that we are willing to turn a blind eye to the disagreements, as indicated in my second reason. Moreover, history clearly shows that other criteria are often deemed more significant.

When a theory is offered as a solution, it is seldom the case, contrary to Popper’s above-quoted view, that we all agree what problems it comes to solve. It is, indeed, all too often the case that opponents expect from a theory that it should solve more problems before they deem it plausible. For example, Bohr’s ability to explain only wavelengths, not enough wavelengths, and no intensities of spectral lines. This limitation is an un­contested historical fact. It was deemed by many scientists at the time to be a strong argument against the plausibility of Bohr’s ideas. His paper on the correspondence principle came to combat that by suggesting new criteria and new avenues of research.

The moral from Bohr’s case is very simple and obvious. Supposing each argument in favour of a thesis is deemed (at least for the sake of argument) perfectly plausible, we still have no consensus about how many such argu­ments make that thesis plausible. We have this divergence of opinion even in science, not to mention engineering, medicine, politics, everyday affairs, or philosophy. How shall we judge or choose between the diverse opinions? By what criterion?

This problem can be reformulated as the problem of desiderata for a plausible thesis:

(PD) What are the desiderata reasonably expected from a thesis before it be, may be, should be deemed reasonable?

Now the question may be tackled both descriptively and prescriptively, allowing, of course, always for the fact that even the best of us fall short of their own standards, not to mention the possibility that our standards are improving, so that our predecessors, even the most illustrious scien­tists and philosophers and wise men amongst them, may fall short on two counts and not only one.

During the whole tradition of western thought there were two and only two answers to the problem of desiderata held consistently enough for any length of time to enable their holders to elaborate on them with sufficient detail and clarity to permit adequate comment on them without exegesis. The first is that of classical rationalism - Greek or of the Age of Reason - according to which a thesis can be deemed reasonable if and only if it is demonstrable. The second is that of all fideistic religious philosophy - medieval philosophy almost exclusively, some but not all modern religious philosophy, and some but not all philosophers who call themselves Marx­ists (rightly or not) - according to which a thesis is plausible if and only if it accords with the faith and then is supported or proven etc. by further arguments.

This brings us back to the very initial datum (d) from which we started. For what is common to both these answers to our problem of desiderata (PD) is that they include the following two assumptions. First, that (PD) is answerable. Second, that if scepticism is true, then (PD) is not answerable. Scepticism is thus rejected by all its opponents a priori on one transcen­dental argument: if scepticism is not rejected, then (PD) is not answerable; hence whether one is a sceptic or not becomes a sheer matter of taste; hence we need not endorse scepticism come what may.

It is, therefore, highly desirable for a sceptic like the present author to try and show how (PD) can at all be attacked by a sceptic. In other words, the problem the initial datum (d) poses to the sceptic concerns rational scepticism:

(RS) is it at all possible for a sceptic to be rational ?

Given (PD), the problem (RS) can be put more specifically thus:

(RD) is it possible for a sceptic to decide reasonably about the reasonableness of the desiderata for a reasonable thesis?

Now (RD) is formulated in a manner most conducive to elicit a nega­tive answer and so condemn scepticism. For, any decision about reasona­bleness which a sceptic may come up with cannot but be circular, and hence unreasonable, whereas (RD) is the search for a reasonable answer. Let us assume, for the moment, that indeed, scepticism is hopelessly cir­cular; the non-sceptic can then reasonably admit the sceptics’ charge of circularity, without being forced into scepticism thereby. The non-sceptic can reason as follows. The sceptics’ criticism, admittedly, deserves study and ought to be demolished regardless of the effort required by such a task. Yet this does not mean that the sceptic wins, no matter how long the attempt to demolish his seemingly plausible argument has failed. For, to succumb to scepticism on this point is simply to replace one circularity by another, thus arriving at no gain and quite possibly, indeed obviously, at some great loss.

This last point, it seems, goes as deep into the anti-sceptical mode of argument as any. It should also be noted that not only classical rationa­lists but also classical fideists have asserted or implied it now and then. It is quite an interesting point, since it embraces a view shared by all non-sceptics of the necessary and sufficient conditions which render plausible a thesis plausibly defended. We have now presented the classical answer to our question (PT): when is a thesis sufficiently defended by plausible argument to count as plausible? And the classical answer is meant to be used in the attempt to vindicate the rationality of most philosophers (who, in accord with our initial datum (d), deny the plausibility of scep­ticism, though they admit it is plausibly defended), be they classical ratio­nalists, or modified rationalists along (PIS) or some such principle, or fideists. What our discussion thus far clearly indicates are the following desiderata, the following necessary and sufficient conditions for the trans­mission of plausibility from arguments to the thesis they defend:

(1) Circularity is bad and should be avoided, at least if at all possible.

(2) A thesis should answer certain specifiable desiderata.

(3) The arguments defending the thesis should cover these desi­derata to an agreed extent.

(4) The agreed extent, as well as the desiderata, should themselves be plausible.

(5) We take as plausible the most plausible thesis we have, prov­ided it is plausible enough by the other criteria. (Otherwise we have to keep searching.)

(The fourth desideratum, it may be noted, is relatively new. It is, for example, the central argument A. J. Ayer employs against the sceptics in his The Problem of Knowledge of 1956: The sceptics win all too easy a victory, but only after they make some quite unreasonable demands put on any thesis which may then be deemed plausible; the extravagant demands, he says, concern both the kind of desiderata and their extent. The fifth desideratum is really a variant of (PIS) and appears in the works of Keynes and Jeffreys on inductive logic early in the century.)

The thesis of the present chapter is that - surprisingly - the above list of five criteria is sceptical, not anti-sceptical. The argument in its defence would hinge on the interpretation of the plausibility of the desiderata which, according with (1), should not be circular, if possible. A bootstrap theory of rationality best answers the five desiderata listed above and is sceptical par excellence, where a bootstrap theory presents series of crite­ria of rationality, each an improvement on its predecessor by its prede­cessor’s own lights. This, incidentally, will remove the circularity from the definition of plausibility since the plausibility referred to in the definien- dum is more advanced than that referred to in the definiens.

This, however, is a mere nicety. There is a substantive and very well known important desideratum which a bootstrap theory of plausible argument should satisfy. It is a principle which has been invented by historians, but which has not yet been introduced into the discussion of the theory of rationality. It is the principle of the historical relativity of rationality:

(HRR) What was rational enough yesterday need not be rational enough today.

Coupled with the classical, rationalistic or fideistic, theory of the deside­rata for a plausible thesis (PD), the thesis of historical relativism of ratio­nality (HRR) yields the thesis of historical relativity of truth:

(HRT) What was true enough yesterday need not be true enough today.

This, incidentally, explains why so few historians of science endorse the thesis of historical relativism of rationality (even though this lands them repeatedly in trouble, as I have illustrated in my Towards An Historio­graphy of Science, 1963, reprinted by Wesleyan University Press, 1967). Most of them endorse the classical theory of rationality as demonstrability or as scientific probability or such, but refuse to accept that truth is relative. They have a point here which is very attractive on both philo­sophical and commonsense grounds. But so is the thesis of historical rela­tivism. This, then, may culminate with a major desideratum and a major thesis.

(Major Desideratum) We want a theory of plausible argument which embraces historical relativism of rationality (HRR) and rejects historical relativism of truth (HRT);

(Major Thesis) To achieve the major desideratum we need notice not only the improvement over the ages of our theories and of our stock of data, but also of our standards of rationality (preach­ed or practiced).

The gratifying corollary of any bootstrap theory of rationality is this. We may, and indeed should, distinguish between a descriptive and a prescriptive theory of plausible argument; yet in so far as there is progress, what is merely prescriptive at one time may become fairly descriptive soon after. In that vein we may avoid charging traditional anti-sceptical philos­ophers with the inconsistency (c) but rather explain our main datum (d) by (c'), the claim that they seem inconsistent. The dilemma we mentioned above, between following one’s own reason and following the mainstream, is likewise resolved in a manner which may stand a little elaboration before the close of this essay.

What seems to characterize the bootstrap theory is the interaction between the framework and its content. Whereas the fideist accepts the framework of faith as final, and whereas the classical rationalist accepts the framework (if any) of demonstration as final, in historical fact frame­works are accepted tentatively. (As Richard von Mises observes, even the Catholic Church could not escape all improvements.) The frameworks enable us to solve some problems locally and declare other problems locally insoluble, or practically insoluble. It is commonsense which tells us what can be taken for granted and what should be considered practi­cally impossible - and the articulation of commonsense is a framework. When a practically insoluble problem is pressing enough, we may offer a solution to it which transcends the framework. The question then will be: can the new solution be the new, or the foundation of the new, framework? The more daring will take the plunge first and act on a framework which is hardly there and which may turn out to be a mirage. As Bunge suggests, it is commonsense to hope to be able to solve a problem within the given framework; it is ambitious to hope to fail in that and succeed otherwise; it is folly not to try to search for a more conventional solution (i.e. a solu­tion within the given framework) first.

The choice between frameworks often follows a theory of rationality, whether more articulated or more intuited. There is, also, the interaction between the choice of a framework and the choice of a theory of ratio­nality. It is no accident that avant-garde defenders of rudimentary frame­works from Galileo to Niels Bohr have also revised (and explicitly) our criteria of rationality.

Finally, the question of whether the old sceptics were rationalists or nihilists is likewise solved. The old sceptics did not have anything like a bootstrap theory of rationality. And so in a sense the rudiment of a theory here presented (largely due to Karl Popper, Mario Bunge, W. W. Bartley III, I. C. Jarvie and others) is not sceptical. Yet, by some lower standard of rationality which is more to the taste of the historically minded, they were eminently rational. Whether the new bootstrap operation theory is more akin to classical scepticism or to classical rationalism becomes less clear- cut than it seemed before. All this is highly satisfactory and should now enable us to declare philosophers who insist on their attempts to answer a sceptic not very rational. With the further development and expression of the detail of the new theory of rationality (c') will have to be replaced by (c) unless, and much more preferably so, our initial datum (d) is no longer true.

All this opens new and exciting vistas. The most gratifying corollary to all this is the solution to the following mystery. Many historically impor­tant debates have been left uncompleted; and no rational reconstruction could complete them in a satisfactory manner. Query: is there a logic to all this? Answer: Yes. A debate led by one set of desiderata may evolve a new set of desiderata which may then lead all participants to rethink and reformulate their answer - or even their questions.

NOTE

¹ By scepticism I mean the view that we ‘cannot defend reason by reason’, as Hume puts it {Treatise, I, iv, 2), or that we can never justify our theory either by proof or by probability.