In this post, we shall explore the test of whether responses to questions are plausible. We shall consider use of the test in philosophy and in history.
The plausibility test is in principle less demanding than the test of whether responses are correct. But it is still important, for two reasons. The first one is that it is not always possible to say whether a response is correct. The second one is that a focus on plausibility brings out certain important requirements for responses to be acceptable, such as that they should not outrage our background understanding and that (in some cases) they should confer Verstehen.
References are given at the end of the post.
The test
Suppose that one seeks a response to a philosophical question, or to the historical question of why events in the human world took the course they did. Such a response may be a one-line statement of some conclusion, or an elaborate account that implicitly answers the question.
We shall use the term "response" to cover the full range of such possibilities. And we shall sometimes be able to speak of responses being correct or incorrect, meaning either that they are answers to questions where those answers could be identified as correct or incorrect in the ordinary sense, or that they are more discursive responses which could nonetheless attract attributions of correctness or incorrectness which would be based on their head-on collisions with facts.
There will however be some responses which are too discursive to collide with facts in the required way, or which do not collide with facts in that way because of the nature of the subject matter of or the approach to it. Concepts of correctness and incorrectness will then be inapplicable. And there will be gradations, with some responses more or less open to classification as correct or incorrect.
When a response is not open to classification as correct or incorrect, an important control is to ask whether it strikes experts as plausible. In this context, plausibility will require making sense, not being outlandish or in serious conflict with how one thinks the world works, and so on. It will not just mean within the bounds of possibility. On the other hand, our intended sense of plausibility is not that a response is to be believed cautiously, or that it is to be assigned some respectable probability of being correct (such as 0.25). Rather, the sense is that adoption of the response would not be unreasonable.
This plausibility test is what will concern us here. When applied in an academic discipline, it will not stand alone. Even if a judgement as to correctness is not expected, there will still be scope for detailed argument as to the evidential and other reasons to accept or reject a response. And what is learnt in the course of such detailed argument should influence judgements as to whether the response is plausible. But the plausibility test will still take investigation a step forward from the stage of detailed argument. It is a safeguard against getting lost in the trees of analysis so that one fails to see the wood of the overall picture, an overall picture which will include the background of existing understanding.
The test also has a role when a judgement as to correctness is envisaged. Even in such cases, once all the detailed work on evidence and reasoning has been done, it is worth standing back and asking whether the response is plausible. This final stage may not be especially worthwhile in disciplines in which one can be confident both that all the relevant evidence has been collected and interpreted correctly, and that its analysis will drive one to an inevitable conclusion as to whether a response is correct. But such happy conditions are only met in physics, chemistry, and a few other parts of the natural sciences. Elsewhere, and certainly across the humanities, the plausibility test is a valuable additional check. This role of the test in writing history was for example highlighted by Geoffrey Elton (The Practice of History, chapter 2, section 5). Elton did not draw our distinction between contexts in which judgements as to correctness are envisaged and contexts in which they are not, but he did stress the need for a stage of detailed analysis of the available evidence.
There is no algorithm for the plausibility test. A judgement as to whether the test is passed will not rest directly on a detailed analysis of evidence or reasoning, even though it may be influenced by matters that have come to light in the course of such an analysis. Rather, whether a response is plausible will simply be manifest to an expert, who will not then seek further justification for their judgement.
One might speak of intuitive judgements. We shall however not do so, except when we refer to other authors' work on intuition. A reference to intuition may be helpful in grasping the notion of judgements that responses are plausible. But the concept of intuition is liable to bring some baggage with it. One can see some of this baggage in discussions of the role of intuitions in philosophy. Philosophers are widely thought to rely on intuitions, but there is also a case to be made that intuitions are not needed (Cappelen, Philosophy without Intuitions). One might argue that the proper role of intuitions in philosophy was not in reaching or directly supporting specific conclusions, but in making judgements of plausibility, albeit subject to the qualification that a response which failed the plausibility test might nonetheless be correct (since intuitions can mislead). We shall not pursue that line of argument here. But we do note that it would be challenged by the fact that a lot of philosophical discussion centres on the scope for intuitions to give direct support to specific conclusions (see the papers in Booth and Rowbottom (eds.), Intuitions).
We should add that expertise does matter. Someone must have had the right kind of education and experience for their judgements to count for much. To describe a response's plausibility or implausibility as manifest, or to refer to intuition, is not to throw the door open to the views of the ill-informed or the untrained.
Examples
We shall now set out some examples of use of the test. We shall include some comments on use of the test in different contexts. Later on we shall focus on the nature and the value of the test itself, rather than on examples of its use.
Our examples will be drawn from the disciplines of philosophy and history. The sense in which a response to a question can be plausible differs as between these disciplines. The normal sense in the areas of philosophy we shall highlight is that a response may be plausible given our own attitudes and habits of thought. In history, the point of reference is not our own attitudes and habits of thought but those of people of the past, along with what was feasible at the time studied. Our own attitudes and habits of thought, along with our current knowledge of people's physical and mental capacities and our grasp of the history of technology, will however be the starting point in compiling the point of reference we need.
Our treatment of the tests in the areas of philosophy we shall highlight and in history as a single test is justified by the fact that in both cases, the point of reference is primarily the nature of human beings. This also opens up scope for applying what would be broadly the same test across other humanities and to some extent across the social sciences. But while there can be good reason to ask whether an account in the natural sciences is plausible, the point of reference would be different enough that one could not say that the plausibility test would be the same kind of test.
Meta-ethics
Various responses to the question of the nature of ethical claims may be accepted by some ethicists and rejected by others on technical grounds. But the most powerful reason for rejecting some responses can be that the responses simply strike one as implausible against the background of a common human understanding of the nature of ethics.
Emotivism may be rejected because it seems plain that an ethical claim is more than an expression of preference, or even an expression of preference with which one would expect others to agree. And one can reject emotivism as implausible on such grounds even before noticing technical concerns such as those raised by the Frege-Geach problem (Geach, "Assertion", pages 463-464).
Some forms of moral realism may be rejected because it seems that there is no space in the world as we generally understand it for moral facts or moral properties on a par with non-moral facts or properties. (One source for such arguments is Mackie, Ethics: Inventing Right and Wrong, chapter 1, section 9.)
Substantive ethics
Suppose that an ethicist argues for some specific response to the question of how to act in a situation of a given type. Other people may agree, or they may disagree but think that the response is nonetheless plausible. As an example of such disagreement, one ethicist might endorse telling small lies to save people's feelings, and another one might say that while their own commitment to honesty was too strong for them to agree, they could still see that the use of small lies for such purposes could be a sensible policy. Whether there was agreement or such eirenic disagreement, the first ethicist's response would pass the plausibility test in the eyes of the second one.
On the other hand, an ethicist might offer a response from which many people would recoil. One such response would be that nobody should ever lie, even to protect someone from a potential murderer. Then the response would in the eyes of most people not pass the plausibility test, and we would start to look for defects in the reasoning or in the premises from which it started.
In order for us to fit the application of the plausibility test to substantive ethics into our discussion, we need to take it that there is scope for disagreement about what to do in situations of different types. An emotivist position would stand in the way of seeing scope for disagreement. But there are other meta-ethical positions, so we shall explore application of the plausibility test on the assumption that there is scope for disagreement about what to do.
Use of the plausibility test in substantive ethics draws on our personal inclinations. We may accept one response to a question as to what to do as reasonable, and reject another one as manifestly immoral, because of our own values. This need not be illegitimate. Ethics concerns how to conduct human lives. So it seems reasonable to give a conspicuous role to how human beings regard it as appropriate to live. But that does give rise to questions. How respectable are the origins of our views on how people should live? And are those views consistent enough between people and across cultures for judgements of plausibility to be thought of as having more value than idiosyncratic preferences?
On the respectability of origins, we may compare reaching a verdict on the plausibility of some response to a question of what to do with the route to conclusions that has been advocated by intuitionists. Intuitionists take the correctness of an ethical claim to be self-evident, without the need for direct support from argument (Stratton-Lake, "Intuitionism in Ethics"; for a full exploration of ways in which intuitionists may reach their ethical conclusions and advocacy of one particular way see Roeser, Moral Emotions and Intuitions). Correctness in the eyes of intuitionists does not however mean obviousness at first glance. It may become evident only after detailed thought which helps to bring out what is salient. Likewise, a judgement of the plausibility of a response will not depend on arguments that support the response directly, but it will be likely to follow detailed argument that relates to aspects of the response other than its plausibility. Having said that, there is a difference between the intuitionist approach and our approach. An intuitionist's claim that it is self-evident that a particular ethical claim is correct is a very strong claim. All conflicting claims are ruled out. To say that it is self-evident that a response which makes the claim is plausible can be to say something much weaker, because several conflicting responses might still be admitted to be plausible.
On consistency of views, we may look to surveys that have been conducted under the banner of experimental philosophy. (Much has been and is being written in this area. Two starting points for what we say here, including our remark about Gettier cases under the heading of epistemology, are Knobe, "Philosophical Intuitions are Surprisingly Robust Across Demographic Differences"; Stich and Machery, "Demographic Differences in Philosophical Intuition: a Reply to Joshua Knobe". On personal identity under our heading of metaphysics see Tobia (ed.), Experimental Philosophy of Identity and the Self.)
There is some evidence from experimental philosophy that people's ethical views do vary across cultures and can be affected by framing. That would count against the worth of views on the plausibility of responses to ethical questions where those views were not based on detailed argument, perhaps reducing the views to expressions of idiosyncratic preferences. Having said that, there are reasons why we should perhaps not be too concerned.
One reason not to be too concerned is that interpretations of the data differ. Not everyone agrees that there are wide variations in views.
A second reason not to be too concerned is that the data often reflect the views of people in general, while we are interested in application of the plausibility test by experts (although sometimes experts are surveyed and turn out to have varying views). There may not be a clear distinction between people in general and experts when it comes to substantive ethics, but there is still a distinction between what people will say when answering a questionnaire quickly and what they would say if they were encouraged to reflect on their views before answering. And those who had already spent some time considering ethical questions could be expected to reflect more thoroughly and more effectively than those who had not.
A third reason not to be too concerned is that even if results varied between cultures, the results obtained in a particular culture could still be seen as valid for people within that culture. The significance of an ethical claim's being thought correct or of a response to an ethical question's being thought plausible would however then have to be limited to what could be concluded from its being thought correct or plausible relative to the relevant culture. No conclusion based on any supposed general correctness or plausibility could be drawn.
Finally, when reviewing data on what people think, we must be sensitive to whether the questions they were asked related to correctness or to plausibility. These can be hard to disentangle. A claim will typically be that in all situations, or in all situations of certain types, some specified conduct is required, acceptable, or forbidden. And the question put to people is quite likely to amount to "Is it required/acceptable/forbidden to perform such and such action in such and such circumstances?". Such a question would relate to the conduct in question rather than to the claim considered as a response to a question. One might conclude from what a subject said that agreement with a response encapsulated by a claim was being shown. For example, agreement that some specified conduct was required would imply a view that a response to the ethical question to the effect that the conduct was required was correct. It would be less straightforward to get at views on the plausibility of responses. Thinking a claim correct would imply thinking that a response which the claim encapsulated was plausible, but it would be left unclear how wide a range of people thought a claim incorrect but still regarded such a response as plausible, and therefore unclear how far views on plausibility of responses varied between different cultures or between segments of the population defined in other ways. One might however at least hope that if ratios of regarding claims as correct to regarding them as incorrect were much the same across cultures or across other segments, proportions regarding corresponding responses to ethical questions as plausible would be much the same too.
Metaphyiscs
In fundamental physics, any plausibility test that is of value will be couched in highly technical terms. It will only be usable by physicists who are deeply immersed in current research. It would be misleading to think of it in the way in which we have been thinking of the plausibility test more generally. And if the results obtained or their conceptualisation turn out to be utterly counter-intuitive to non-experts, so much the worse for those people. Any objection that a non-technical plausibility test was failed would rightly be ignored by physicists.
Turning back to philosophy, we do reasonably demand a commonsense metaphysics of space, time and matter. That is however allowed us, with no need to challenge physics. We may borrow an image supplied by Max Tegmark, without needing to accept his whole theory. The world as described by counter-intuitive physics can unproblematically be seen as giving rise to the consensus reality of space, time, objects, and the observable interactions of objects within which we conduct our lives (Tegmark, Our Mathematical Universe, chapter 9).
There are other areas of metaphysics in which there is not the same need to accept the supremacy of potentially non-intuitive physics and then recover our everyday world.
One example is given by personal identity. A response to the question of what constitutes personal identity over time may be reviewed to see whether it offers a secure identity through all sorts of changes. These will include both gradual changes such as those of maturing and ageing, and sudden changes such as those caused by brain injuries. And the identity must be substantial enough to fulfil its practical roles in settling to which people we relate in certain ways (as family, friends, colleagues, and so on), in settling attributions of responsibility and property, and so on.
How the plausibility test can affect debates is interesting. Philosophers will imagine strange cases, including brain swaps, brain divisions, and successful and interrupted teleportations. Then they will precisify or amend everyday notions of personal identity to find notions that will yield plausible verdicts on those cases. This will be an initial application of the plausibility test. But the test must be applied again in relation to cases that actually occur.
It will usually be trivial to show that a notion of personal identity yields plausible verdicts in the most straightforward everyday cases. But there may be difficulties in less straightforward cases, such as extreme memory loss, where we naturally want to say that identity is in fact preserved but have difficulty in doing so. There may also be concern that a notion provided by philosophers is not robust enough to meet our everyday requirements. For example, a criterion based on a sense of attachment to one's past or to one's forthcoming conscious life might be thought to be too focused on ephemeral mental phenomena. And philosophers like Derek Parfit (Reasons and Persons, chapter 12) who say that identity is not the important thing may be thought to have insufficient respect for a notion that is central to our personal and social lives. In all the cases in this paragraph we may see applications of the plausibility test, both by philosophers and by other people who take an interest. And even if one were to discount the views of non-philosophers, a notion that they would criticise as implausible might well also be criticised as implausible by many philosophers.
Another example is given by the question of human free will. From the inside, we have a clear sense of making our own decisions and acting on them. But from the outside, we may be told that all of our thoughts and actions as they may be characterised in human terms supervene on physical reality, and that this reality's evolution reflects a mixture of determinism and randomness.
(For an introduction to views we now mention see Fischer, Kane, Pereboom and Vargas, Four Views on Free Will.)
Some philosophers will tell us that free will is indeed illusory. Such responses to the question of free will would fail any plausibility test, even among philosophers, until good reason had been given to think that there was no alternative.
Other philosophers, the libertarian incompatibilists, will tell us that while the physical world cannot accommodate free will, we have it anyway. Such a response might fail the plausibility test not because it would be disappointing, but because it would be unclear how free will would arise.
Finally, there are the compatibilists who work on our initial conceptions of free will. Schopenhauer located freedom in our freedom to do what we will, and dismissed the idea of our being able to will what we will (Prize Essay on the Freedom of the Will). More recent philosophers have developed the notion of guidance control: our choices and actions reflect our own personalities because lines of causal influence flow through our brains and bodies, but this does not imply that things could have turned out differently by virtue of influences originating within ourselves and not directly or indirectly prompted by any prior events in the external world. Compatibilist responses to the question of free will would seem to have the best prospect of passing the plausibility test. This reflects the fact that a response can on reflection be found plausible by virtue of some adjustment to our initial demands, in this case an adjustment to everyday conceptions of free will.
Epistemology
Most people are confident that many facts are known by humanity, and that they themselves know a fair few. Even experts in various disciplines, well aware of the difficulty of making discoveries and the risk of error, take the same view of the contents of their disciplines. Responses to the question of how to define knowledge that would make knowledge very hard to obtain, for example definitions that would require no possibility of error, would therefore fail the plausibility test.
A more interesting case is that of definitions which discriminate between examples of knowledge and non-knowledge in ways that provoke debate, both among people generally and among experts in various disciplines. Typically the examples are justified true beliefs where there has been some element of luck, for example through harmless or even positively helpful reliance on false premises or on defective reasoning. A response that supplies a given definition may be thought to fail the plausibility test if the definition too often classifies such beliefs as knowledge when people are inclined not to do so, or if it too often classifies them as non-knowledge when people are inclined to think of them as knowledge.
As with substantive ethics, such verdicts as to plausibility can legitimately have force. The facts that we know may not be human constructs, save to the extent that we have invented specific concepts to express those facts, and even then the independent world may have forced us to use certain concepts and not others. But the notion of knowledge is our own construct. It has been created to capture important facts about our relationship to the world, such as the fact that people with knowledge tend to get on better than people without it. The notion has been tailored to capture the fact that there is something more advantageous than true belief, following the issue raised by Plato (Meno, 97-99). And the verdicts on individual beliefs that a definition gives had better not be too far out of line with what people would think prior to philosophical reflection.
But as with substantive ethics, we must ask about the consistency across cultures of pre-philosophical thought. Again, experimental philosophy has something to say. Views on Gettier cases and the like do vary. But as with substantive ethics, we can ask how great the variation really is.
One difference from substantive ethics is that it is harder with knowledge to minimise concerns about a lack of consistency by saying that views may be for particular cultures rather than for the whole of humanity. Cultural relativity need not be overly troubling in relation to substantive ethical views. Different people live in different circumstances, with different histories. So different judgements of good and bad, right and wrong, may be apt to different societies. But the notion of knowledge is closely tied to the notion of truth. And we tend to regard both the notion of truth and the set of propositions that are true as universal.
History
At first glance, the discipline of history might seem to amount to the narration of facts on the basis of evidence. That would leave no room for a plausibility test, save in making judgements when the available evidence was not decisive.
But history goes far beyond chronology. Historical accounts impute motives, they abstract from factual details to identify political, economic and social forces, and they give narratives that are powerfully explanatory and that confer understanding on those who read them.
Having said that, history is far from being a natural science. There is no scope for repeated experiments, nor for precise and decisive calculations of the extent to which evidence supports conclusions. And both the motives of human beings and the causal links between what they think and what they do are too ill-defined to admit of comprehensive calculation.
In such a context, there is work for the plausibility test to do. Are portrayals of people's thoughts, fears and desires, and identifications of reasons for significant actions, plausible?
The test will usually be passed in published work, because historians are also human beings and will have a good inner sense of what would be realistic portrayals of the people they study. But we may still see the test as having played a role in processes of thinking, writing and re-writing, perhaps playing that role without historians' being conscious of its having done so.
The plausibility test acts as a filter to dispose of responses to questions of why events took the course they did which would not be much good, rather than as a way to show that a given response which passes the test is correct. In the context of history, the test may first be applied to see whether Vestehen (understanding) is conferred. Its conferral would be a good sign, given the need for consonance with our background understanding of people and the world if it is to be conferred. Then the test may be applied in two directions, running between Erklären (explanation in a broadly scientific sense) and Verstehen.
The first direction runs from Erklären to Verstehen. Suppose that some quasi-mechanical causal account has been given as a response to the question of why events took the course they did. If the account is good enough, it will amount to Erklären. But is it good enough? Given the lack of mechanical precision in the world as viewed by historians, it is useful to have a test that brings in a different set of requirements. This is what the plausibility test can do. It can be used to assess whether the quasi-mechanical detail in the account affords a route to Verstehen. The move is from testing the proposed mechanism by reference to technical and quasi-mechanical principles to testing whether the account would resonate with us on the basis of our common understanding of how human beings and the world work.
The second direction runs from Verstehen to Erklären. An account may seem to confer understanding, and that may be checked in an initial application of the plausibility test. But an impression of understanding may be too easily given. If understanding depends on accepting an account that assumes a pattern of causes and effects which is in quasi-mechanical terms implausible, then the account should be rejected as an implausible response to the question of why events took the course they did.
Historians must be cautious when checking for plausibility by reference to Verstehen, whether in an initial application of the test or to see whether the quasi-mechanical detail provided affords a route to Verstehen.
The need for caution arises from the fact that principles of human motivation and action, the satisfaction of which in an account is required for the account to confer Verstehen, vary as between societies. Given that the test should be of whether the people studied could plausibly have acted as described, the relevant principles will be the ones of that society. (In anthropological terms, an emic approach should be preferred to an etic one.) These relevant principles may not be the ones that first occur to historians, especially if the historians come from a society other than the one being studied or if they are looking back many centuries. Just how easy it can be for principles to differ can be seen from one anthropologist's attempt to explain the story of Hamlet to members of a west African community (Bohannan, "Shakespeare in the Bush").
A general consideration of the test
We now move on from specific applications of the plausibility test to a more general consideration of its worth.
Plausibility and correctness
A judgement that a response is plausible is not always a judgement that the response is uniquely correct or that it is among the correct responses. It is however at least a judgement that the response should not be discarded yet, but should continue to be kept in play and explored as a useful way to look at relevant features of the world. It is therefore at least a judgement that the response should not currently be regarded as incorrect, because responses regarded as incorrect are never worth keeping in play except perhaps as part of a lateral thinking exercise in which they may prompt new thoughts.
There are three possibilities to consider.
The first possibility is that it was expected that one response would deserve to be regarded as correct. Then the identification of only one response as plausible might amount to a judgement of its correctness.
The second possibility is that it was expected that several responses would deserve to be regarded as correct. If it was thought that all plausible responses deserved to be regarded as correct, a judgement of plausibility would amount to a judgement of correctness. (This case might not be reducible to the one-response case. Differences in the aspects of the topic on which responses focused might suffice to obstruct simply taking their conjunction and presenting that as a perhaps unwieldy single correct response.)
The third possibility is that the nature of the discipline or of the topic would make it inappropriate to assert that every response could be shown to be correct or shown to be incorrect, so that there would be space for an intermediate category of responses which, while plausible, could not have their status as correct or as incorrect determined. Then a judgement of plausibility would not in general amount to a judgement of correctness, although it might do so in relation to some responses. (There might or might not be responses which could never have their status determined. It might only be that at any one time, there would be responses which could not have their status determined in the near term. As the discipline progressed, they might have their status determined or they might cease to be of any interest, but it would be likely that new responses of indeterminate status would also come into play.)
When a judgement of correctness is made, a judgement of plausibility becomes redundant save as a path to a judgement of correctness. Correct responses have to be accepted whether one likes them or not. The favourable result of any test of plausibility would play no more than a supporting role, showing the absence of a certain kind of objection to a response. There is also pressure on experts to resolve any disagreement as to correctness.
It is when no judgement of correctness is made, or when conflicting judgements of correctness are made by different experts and there is no prospect of resolving their disagreement in the near term, that the role of plausibility becomes interesting. A judgement of plausibility is not rendered redundant, but may be valuable in its own right. So a test of plausibility may make a real contribution, moving us forward from a plethora of possible responses either to one plausible response, or to a modest range of plausible responses.
We should think in terms of a range of responses, however many responses are currently in play. Even if only one is in play, we should allow for a potential range that would encompass responses which could be introduced. That possibility would be interesting because while there might be grounds to think that only one response could be correct, and there would always be reason to think that when responses conflicted no more than one of them could be correct, there would not in general be reason to think even that only one out of a range of conflicting responses could be plausible, at least not when determinations of correctness were not expected to be available in the near term.
It may be perfectly possible to consider each member of a set of responses plausible, even if various responses in the range would not sit comfortably together or would contradict one another. This would however need to be limited to saying that each one was plausible individually, not that the conjunction of all of them would be plausible.
If conflict fell short of contradiction, for example because different responses identified different ethical or experiential considerations as central while each allowed some role for considerations picked out as central by others, or because different responses identified different factors in the explanation of some historical event as the most significant factors, there would be a hope and maybe an expectation that either current approaches to the question or knowledge of the world would in due course advance so that some responses would drop out and the conflict would be resolved. It would however be possible to live with the thought that the conflict might never be resolved. If there was contradiction, there would be a more pressing need to resolve the conflict. Then a thought that the conflict might never be resolved would amount to a thought that our grasp of the world and of life might be irremediably inadequate.
One feature of the humanities would contribute to making it tolerable to regard several conflicting responses as acceptable. This is the fact that a given response is prone to carry with it a given way to weigh up competing considerations and sometimes a given way to interpret evidence. So someone who favours one response may see someone who favours another response not as debating with them against a background of a completely shared understanding of the significance of different considerations and of the meaning of the evidence, but as debating against a background that was in some respects different. The effects would be a bit like that of perspective-taking in the natural sciences, where what might be seen as tension between different accounts of the same phenomenon can be defused by a recognition that different scientists may approach a single topic from different perspectives.
The significance of tolerance
We now turn to the significance of the scope to tolerate several conflicting answers as plausible. We shall explore what it might mean for the worth of a response's passing the plausibility test, not merely in cases in which several conflicting responses are in fact considered plausible, but in general. We shall say something about the nature of the test which will be relevant whether or not, in a particular case, several conflicting responses all pass it.
A judgement of plausibility is at least a judgement that it makes sense to look at some feature of the world in a particular way. It is stronger than a judgement that it is pedagogically helpful to look at the feature of the world in that way. Pedagogical helpfulness will reflect the psychology of students. Responses that experts would regard as misleading may turn out to be helpful. We on the other hand are concerned with what fully trained experts, who would not need the same level of assistance as students, would say about keeping possible responses in play.
Having said that, a response may be plausible in our sense when the usefulness of keeping it in play reflects the powers of thought of experts, while some hypothetical more advanced being would regard the response as misleading. Such a being might view it in the ways that human experts would view ways to look at the relevant feature of the world which were needed only to help students. We cannot have more than a speculative grasp of what the powers of such a more advanced being might be, so we cannot tell which answers might be downgraded in the eyes of such a being.
One might argue that such advanced beings were already among us, in the form of artificial intelligence systems. We might declare certain ways to look at features of the world of which the systems appeared to have no need to be of merely pedagogical helpfulness. We would however be reluctant to do so if, as would be entirely possible, we could not grasp how such systems thought. Dispensing with our own ways to look at features of the world would then leave us with artificial intelligence systems which could assure us that the evidence found should not surprise us, or which could make accurate predictions, but the systems would not give us any understanding. Concerns about degrees of sophistication and comprehensibility of different responses would however mainly arise in relation to the natural sciences, rather than in relation to the humanities which are our concern here.
While a judgement of plausibility is stronger than a judgement of pedagogical helpfulness, it is weaker than a judgement that the world actually is as described, at least when the judgement of plausibility falls short of a judgement of correctness. It is weaker than such a factual judgement even if the factual judgement is read in ways that either anti-realists or perspectivists in the philosophy of science might advocate. (We take perspectivists to read factual judgements as saying "From this perspective, the world is like this".)
The comparative weakness of a judgement of plausibility explains why it is possible to judge several responses plausible even when they contradict one another. If responses were judged to say how the world was, such tension between them would be intolerable. If one description of the world was thought correct, contradictory ones would have to be thought mistaken. This is not because the world is known not to be an awkward place which could encourage contradictory descriptions. The existence of sensible if inconclusive discussion about adjusting logic in the face of quantum mechanics shows that we cannot be confident of the world's not being so awkward. Rather, our aversion to regarding contradictory responses as correct springs from the fact that doing so would undermine our notion of judgements of correctness as saying how the world actually was and implying decisively how it was not. If our judgements of plausibility do not amount to judgments of correctness, we can tolerate contradiction more easily. Contradiction will however remain uncomfortable.
Likewise, the comparative weakness of a judgement of plausibility makes it easier to judge several responses plausible when they would conflict with one another in some way that fell short of contradiction than it would be to judge all of those responses correct. The prospect of the world's being awkward enough to encourage conflicting but non-contradictory descriptions is more tolerable than that of the world's encouraging contradictory descriptions. It would undermine not our notion of correctness, but our confidence that we were on the high road to a full understanding. And finding several conflicting but non-contradictory responses plausible would not be as depressing as thinking we had to regard them all as correct. It might indeed be encouraging, in that it showed we were capable of developing several lines of enquiry without knowing which one would turn out to be the most fruitful.
We can see one way in which it can be tolerable to keep conflicting responses in play by reflecting on how things are in certain types of philosophy and in history. An important feature of these areas of work, and of some other work in the humanities, is that decisive judgements as to the truth of assertions can often be expected to lie permanently out of reach. This is so because in order to say anything interesting, one has to go beyond what the evidence requires one to say or not to say, and to interpret it in ways that are optional. Given that the crunch point at which final verdicts of truth and falsity are announced is not expected to be reached, conflicting responses can be tolerated because their coexistence will not be forced to come to an end. This does not however mean that anything goes. There are still standards to be met. For standards in history see Baron, Epistemic Respectability in History.
The value of the test
As we have already said, the fact that a response passes the plausibility test does not show that it should be taken to be correct, at least not without some substantial additional conditions being met. And we can often tolerate having conflicting responses to the same question which all pass the test. The test is only a filter to reject some responses, while potentially leaving several others in play. Does all this mean that the test is too undemanding for its administration to have value? No, it does not.
The fact that the test is only a filter to rule out some responses does not undermine the whole process of review of responses, because it is not the only test. It will normally be administered in addition to a detailed analysis of evidence and reasoning.
But why should such a filter add much to detailed analysis?
One reason is that detailed analysis cannot be as conclusive in the humanities, or indeed in the social sciences and some parts of the natural sciences, as it can be in physics and chemistry. Forms of evidence are diverse enough for there to be scope to overlook relevant evidence, and the evidence that is found can be misinterpreted.
A second reason is that evidence may be open to alternative interpretations, all arguably legitimate, in the light of different background theories. The use of such theories may be required in order to make the evidence speak at all, so it is not to be avoided. From within a theory, its interpretation of the evidence cannot be seen as illegitimate, and there may be no neutral standpoint from which to weigh up the alternative theories and their approaches to the interpretation of evidence. Then the plausibility test, based on general principles which are not specific to particular theories, may help to screen out theories which fall short in some way. The test would typically do so by finding that responses in some way failed to make sense, implying that there might have been something wrong with the theories under which they were produced. The test would however still not offer a neutral standpoint from which theories could be examined, because it would not have the tools with which to examine theories directly. Indeed, its use might lead to the identification of a theory as unsatisfactory without specifying the defects in that theory, merely condemning it by reference to its results.
A third reason is that in the humanities in particular, there is a legitimate demand for Verstehen. Responses to questions must bear an appropriate relationship to the nature of human readers, one that really does confer understanding. It is hard to check for that through detailed analysis. A general test like the plausibility test is what is needed.
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