© LOGOS & EPISTEME, VI, 1 (2015): 95-111 A DAVIDSONIAN RESPONSE TO RADICAL SCEPTICISM Ju WANG ABSTRACT: In this paper, I attempt to show how Davidson's anti-sceptical argument can respond to the closureRK-based radical scepticism. My approach will focus on the closureRK principle rather than the possibility that our beliefs could be massively wrong. I first review Davidson's principle of charity and the triangulation argument, and then I extract his theory on content of a belief. According to this theory, content of a belief is determined by its typical cause and other relevant beliefs. With this constraint on content, I argue that doubt must be local. Furthermore, since one cannot rationally believe that one's commitment to the cause of beliefs could be false, our commitment to the denial of a sceptical hypothesis is not a knowledge-apt belief. Therefore, the closureRK principle is not applicable to rational evaluations of this commitment. As a result, the closureRK-based sceptical argument fails while the closureRK principle remains. KEYWORDS: closureRK principle, radical skepticism, doubt and belief, knowledge-apt belief 0. Introduction Donald Davidson is a prominent anti-sceptical exemplar in contemporary philosophy. He famously argued that belief is in its nature veridical.1 If the claim were true, one significant presupposition of scepticism would be unattainable. In Davidson's view, scepticism regarding the external world presupposes that our beliefs about the external world could all be false. The idea of massive error in our beliefs can be motivated by considering ordinary cases where our senses present us misleading information. If we grant that a perceptual belief is fallible in particular cases, then it seems that nothing stops us from generalizing such a possibility of error. As far as we cannot exclude the possibility of massive error, scepticism is on the way.2 Accordingly, Davidson's theory aims to offer compelling reasons as to why such a possibility is unintelligible. 1 Donald Davidson, "A Coherence Theory of Truth and Knowledge," in his Subjective, Intersubjective, Objective (Oxford: Clarendon Press, 2001), 146. 2 Notice that apart from the idea of massive error, scepticism also needs the closure principle to bring it happen. Ju Wang 96 The standard formulation of the closure-based sceptical argument consists of the following three claims where S is a subject, Q is the denial of the sceptical hypothesis and P is an everyday proposition: A. S cannot know that Q. B. If S knows that P, and S knows that P entails Q, then S knows that Q. C. S knows that P. Here is the idea behind this formulation: in order for us to know something, we must be capable of ruling out the possibility of the sceptical hypothesis. If this requirement cannot be met, our epistemic status would be too weak to claim any knowledge. Notice that massive error in beliefs supports claim A implicitly. The reason is simple: in a sceptical scenario, ex hypothesi, our beliefs could be massively wrong while we continue believing them to be true. Thus, we cannot know whether the sceptical hypothesis obtains. If Davidson can offer good reasons to refute or dismiss the idea of massive error, then surely we are in a position to tell why claim A is not acceptable in the sceptical argument. Along one line, we can focus on how to interpret Davidson's argument and whether his argument is sound, but I won't pursue this line in this paper. Rather, I attempt to develop Davidson's anti-sceptical argument against claim B. We can respond to the closure-based sceptical argument by rejecting the second claim or what is normally called the closure principle. In order to focus upon a plausible version of B, let's look at a more specific principle formulated by Duncan Pritchard (forthcoming): The ClosureRK Principle If S has rationally grounded knowledge that p, and S competently deduces from p that q, thereby forming a belief that q on this basis while retaining her rationally grounded knowledge that p, then S has rationally grounded knowledge that q.3 At first sight, this principle is more demanding than the closure principle in that while the closure principle only demands that knowledge be under known entailment, the ClosureRK principle requires that knowledge be based on a rational ground which can preserve across a well-conducted rational operation by a believer. However, the ClosureRK principle is also defensible for this reason: it captures the core idea that knowledge is a cognitive achievement, thus competent deduction, as a paradigm way of a rational process, cannot undermine our rational ground for knowledge. Therefore, what motivates the closure principle motivates 3 Duncan Pritchard, Epistemic Angst: Radical Skepticism and the Groundlessness of Our Believing (Princeton: Princeton University Press, forthcoming in 2015). A Davidsonian Response to Radical Scepticism 97 the ClosureRK principle as well. Pritchard further argues that what underlies the ClosureRK principle is the idea: the reasons for believing p serve as reasons for believing any logical entailment of p. Pritchard thereby names the idea the universality of reasons thesis. Contemporary epistemologists generally agree that knowledge entails belief. Specifically, knowledge is responsive to a rational process and belief is knowledgeapt. A knowledge-apt belief is a belief that aims at truth. In what follows, I will limit my discussion to knowledge-apt belief. Given this, a quick point is that if we cannot bear a knowledge-apt-belief attitude towards a proposition, then this proposition is not even in the market for rational knowledge. I will proceed as follows: In sections 1-2, I review Davidson's theory of radical interpretation, the principle of charity and triangulation. In section 3, I extract Davidson's view on doubt and belief and argue that doubt is in its nature local. What follows in section 4 is an attempt to show how a Davidsonian response to the ClosureRK-based sceptical argument proceeds by denying that the sceptical hypothesis does not obtain is a belief. In the ending section, I give some comments on this solution. 1. Radical Interpretation and Principle of Charity Davidson appeals to the notion of radical interpretation in order to develop a theory of language, or more broadly, a theory of understanding. What is radical interpretation? Basically, it's a fantasy scenario where one is in a completely new place, say a remote island or an aboriginal tribe. One tries to understand residents by figuring out what they believe and what their utterances mean. However, the interpreter has no prior knowledge of either the speaker's beliefs or the meanings of the speaker's utterances. In such a scenario, what are available to the interpreter are only publicly observable behaviors and utterances, or more specifically, S's holding a sentence true at a certain time and a situation. Thus, the interpreter has to adopt a third-person stance to understand something internal to the speaker. Nonetheless, understanding a speaker seems to be extremely difficult as Davidson remarks, since there is interdependence between a speaker's belief and the meaning of her utterance. Given the interdependence, it follows that the interpreter cannot assign a meaning to a speaker's utterance without specifying the speaker's beliefs, and one cannot identify the speaker's beliefs without figuring out what her utterances mean. To see this, we need to think what we normally do in everyday life. We express our beliefs by uttering words or sentences. In doing this, we must also be competent to use our idiolect so that we are able to find the appropriate way to Ju Wang 98 express our beliefs. For instance, if I intend to express my belief that London is a modern city by uttering the sentence "London is a modern city," then I am doing right since I choose the proper sentence to express the corresponding belief. Otherwise, my expression would be improper. Then suppose we are to interpret someone who utters the very sentence, how can we start our interpretation? The problem is we cannot assign the meaning London is a modern city to S's utterance if we are ignorant of what S believes. By the same token, we cannot figure out what S believes unless we already have an idea of what her utterance means. If we plan to assign belief and meaning to a speaker in radical interpretation, the speaker's holding true attitude can be explained by more than one interpretation. Suppose S utters 'X', then I take S to hold her sentence X true and give two interpretations as follows: (Int1) S believes P (Int2) S believes Q X means that P X means that Q Hence S holds X true Hence S holds X true In (Int1) and (Int2), both interpretations provide an account of why S holds X true based on an ascription of S's utterance and S's belief. However, potential rival interpretations are countless. Thus, it would be very difficult for us even to set off the interpretation for a single utterance. That multiple interpretations are available for one utterance indicates that belief and meaning are co-varied in explaining one's holding true attitude. Without more constraints, we can't determine which interpretation is the optimal. In order to resolve this problem, Davidson appeals to the principle of charity. Roughly put, the principle of charity requires that the interpreter and the speaker share mostly true and coherent beliefs, by the interpreter's own light. How can this principle help solve the problem of interdependence between belief and meaning? Notice that the interdependence problem arises out of the covariation of meaning and belief. Therefore, we are supposed to determine meaning while maintaining belief as a constant factor as far as possible. With belief being fixed, we can ascribe meaning to one's utterance, and those ascriptions are not absurd in our own light. For example, let S say "there's a hippopotamus in the refrigerator." Davidson remarks that we prefer interpreting S's utterance as saying that there is an orange in the refrigerator rather than there is a hippopotamus in the refrigerator.4 The reason is that we find the former interpretation to be more reasonable when S's further account includes descriptions that we normally take 4 Donald Davidson, "On Saying That," in his Inquiries into Truth and Interpretation (Oxford: Clarendon Press, 1984), 101. A Davidsonian Response to Radical Scepticism 99 an orange to fit better, rather than a hippopotamus. Notice, here we take our beliefs about orange into consideration when determining the meaning of S's utterance. Brueckner objects that guaranteeing that the interpreter and the speaker share beliefs as much as possible, as in the orange case, would result in ridiculous interpretations when the speaker and the interpreter live quite different lives, such as when an interpreter from tropical area ascribes a belief to a Siberian resident that he has never seen snow.5 What's worse, not only is massive agreement in beliefs not enough, but also it won't be better if we add that we assign similar beliefs to a speaker by referring to similar evidence. The key reason is that my envatted counterpart and I have subjectively indistinguishable perceptual experience, and therefore our evidence for beliefs is on a par. Accordingly, it is required by charity to attribute true and coherent beliefs to her, but this move is at odds with my intuition that a BIV cannot have true beliefs about her environment. Moreover, unless we as interpreters have generally true beliefs, our attributed beliefs to others could not be true. In other words, it makes no sense to assign true beliefs if interpreters are massively wrong. Thus, there is something wanting in defense of the principle of charity, and Davidson is also aware of the weakness. Later on, Davidson puts forward the omniscient argument, but it's not what we should pursue here because he renders it as a useless argument on the one hand, and there are fatal problems with this argument on the other hand.6 Therefore, I will proceed to Davidson's triangulation argument which takes over the role of omniscient argument as articulating and defending the principle of charity. 2. Triangulation What is lacking in the previous formulation of charity is that, only massive agreement and similar evidence cannot make beliefs generally true. A crucial problem is if we can't determine the cause of beliefs, it is still possible that our beliefs are mistaken in the main since our beliefs may be caused by the evil demon rather than an objective world. Consequently, Davidson has to settle the issue how a belief gets its content. In "Rational Animals," Davidson suggests a triangulation model of radical interpretation: 5 Anthony Brueckner, "Charity and Skepticism," Pacific Philosophical Quarterly 67 (1986): 26468. 6 Donald Davidson, "Reply to A. C. Genova," in The Philosophy of Donald Davidson, ed. Lewis Hahn (Chicago: Open Court, 1999), 192-194. Ju Wang 100 If I were bolted to the earth, I would have no way of determining the distance from me of many objects. I would only know they were on some line drawn from me towards them. I might interact successfully with objects, but I could have no way of giving content to the question where they were. Not being bolted down, I am free to triangulate, one that requires two creatures. Each interacts with an object, but what gives each the concept of the way things are objectively is the base line formed between the creatures by language. The fact that they share a concept of truth alone makes sense of the claim that they have beliefs, that they are able to assign objects a place in the public world.7 A triangulation, just like a triangle in geometry, involves three points and three lines. It consists of an interpreter I, a speaker S, an object O, and lines connecting I, S and O respectively. I-O and S-O are both causal relations between a subject and the external world, while S-I forms a social network between two subjects. In triangulation, both subjects respond to the object located in a shared world and react to each other's reactions. Why appeal to such an argument? I suppose Davidson is in need of a new argument to justify the principle of charity and to establish that belief is in its nature veridical. How can he achieve this task via triangulation? Davidson urges that, we must, in the plainest and methodologically most basic cases, take the objects of a belief to be the causes of that belief.8 However, in determining the cause of a belief, we have to face the ambiguity of the concept of cause. The ambiguity is two-fold. On the one hand, one cannot locate the object that causes one's belief. The cause of one's belief may be distal or proximal, and it may lie at any point along the I-O line; on the other hand, one cannot determine what aspects of the object typically cause one's belief. In triangulation, what is essential is that when two causal lines converge, each can locate the cause of their belief. The reason is that what causes my belief may stand at any point along the I-O line, and so does whatever causes your belief. Nonetheless, what causes your belief can't be something in my mind or stimuli in by brain (i.e., proximal), therefore the cause of my belief must be somewhere in the external environment where our causal lines meet. Is the convergence enough to specify the cause of belief? The answer is no. Davidson needs the I-S line to identify the cause of belief as well. To see this, recall the orange in the refrigerator case. Even interpreter and speaker can locate where the cause of their beliefs is, 7 Donald Davidson, "Rational Animals," in Subjective, Intersubjective, Objective (Oxford: Clarendon Press, 2001), 105. 8 Davidson, "A Coherence Theory," 151. A Davidsonian Response to Radical Scepticism 101 they have a disagreement about what the object is. Only through further descriptions, they can settle whether the cause is an orange or a hippopotamus. Those further descriptions are not only further information that can disambiguate the cause of belief, but also a requirement for a rational belief. The role of I-S line is significantly vital in two aspects. Firstly, it provides the space of error. Since only in communication, both interpreter and speaker are in a position to identify the cause of their beliefs. When each alone attributes the cause of beliefs or when they assign beliefs to each other without communication, they sometimes make mistakes. However, it is implausible to correct this mistake by oneself since one cannot distinguish what is true from what is false. Communication provides a space in which one could realize that the truth of one's belief is determined by an objective world which one shares with others. Secondly, it seems that what is at issue here is language communication. It is true that we can identify the cause of a belief only in communication, but communication is not only a matter of language, it's also a matter of thought. In order to specify an orange as the cause of a belief, the interpreter considers several sentences of the speaker, not only the first claim that "there's a hippopotamus in the refrigerator." Those sentences help to determine whether the speaker is talking about an orange or a hippopotamus. Meanwhile, given that sentences express thoughts, we can infer that if the speaker's belief is about an orange, a set of further beliefs should also be endorsed by the speaker. Obviously, Davidson is here invoking semantic holism. Semantic holism is the thesis that meaning of a sentence is determined by other related sentences in the language. Even though it is impossible to draw a clear line where related sentences end, I suppose the core idea behind it is still plausible. We can motivate semantic holism by considering the indeterminacy of interpretation.9 In developing a theory of meaning for a language, one must deal with the totality of utterances in that language. However, given a certain finite amount of evidence, we can have more than one theory of interpretation that suffices to account for the evidence. Different interpretations can differ in a particular assignment of meaning and belief, but would be equally plausible in explaining the total evidence. It is the whole sentences and beliefs that have equally satisfying explanation to one's action regardless of differences in minor places. What follows from the indeterminacy of interpretation is the holistic nature of meaning and belief rather than a practical or cognitive limitation in interpretation. Another 9 Jeff Malpas, "Donald Davidson," The Stanford Encyclopedia of Philosophy, Summer 2014 Edition, http://plato.stanford.edu/archives/sum2014/entries/davidson/. Ju Wang 102 reason to support semantic holism is to appeal to the inferential property between meaning and belief. For instance, 'orange' is inferentially connected to 'fruit,' and further inferentially connected to 'non-meat'; similarly, my belief that this is an orange is inferentially connected to my belief that this is a fruit and that this is not meat. The holistic structure of meaning and belief not only serve as an explanatory tool in accounting for one's mental content, but also constitute a normative regulation on any attribution of meaning and belief. Therefore, to entertain a singular proposition is not possible in Davidson's view; at least the rationality of thought and language can only be appreciated in a holistic structure. To summarize, in the triangulation model, the content of a belief is determined by two factors. The first is the cause of the belief, which is indicated by I-O and S-O lines; the second is other relevant beliefs in the belief system, which is also a social trait embodied in the S-O line. So far, Davidson may have plenty of resources to argue that belief is in its nature veridical, and surely one can proceed to argue against the possibility of massive error. However, I will bear in mind his view on the content of belief and then turn to his comment on doubt and belief. 3. Belief, Doubt and Content When it comes to beliefs, Davidson emphasizes that a belief must have a determinate content. What determines a belief's content then? According to the previous discussion, we can specify the content of a belief by relating it to a world of further beliefs or its typical cause. See the following remark of Davidson: Not only does each belief require a world of further beliefs to give it content and identity, but every other propositional attitude depends for its particularity on a similar world of beliefs.10 By relating a belief to other beliefs, we can determine the very content of the belief in question. This claim is also supported by the semantic holism endorsed by Davidson. And since other propositional attitudes, like doubt, hope and wishful thinking, etc. depend on beliefs, we can only proceed to doubt by having beliefs in the first place. Davidson thus gives priority to belief among different propositional attitudes. Why is this plausible? To see this, let's have a look at the following example. When S doubts that there is a tree in the garden, she must have something in mind to support her doubt. These things in mind are beliefs she actually holds, like that a tree is an object with branches and trunk and that a 10 Davidson, "Rational Animals," 99. A Davidsonian Response to Radical Scepticism 103 garden is a space where plants are cultivated and displayed. Without those further beliefs in play, her doubt regarding the proposition would be void of content and thereby nonsense. The same holds for other propositional attitudes like hope that there is a tree in the garden, or fear that there is a tree in the garden. The core idea is that, in order to have a propositional attitude towards a proposition, or having a thought, it is necessary to have a network of related beliefs which serve to make the propositional attitude in question intelligible and contentful. Therefore, the starting point of any propositional attitude is belief, and so is doubt. In terms of doubt, Davidson proposes a constraint: It is only after belief has a content that it can be doubted. Only in the context of a system tied to the world can a doubt be formulated.11 Davidson's claim here can be split up into two aspects. One is how to have a doubt; the other is how to formulate a doubt if we had it. However, on closer inspection, I suspect Davidson has only one thing in mind. It is obvious that the logic of doubt, according to Davidson, presupposes belief with a content. That is to say; it is not possible to doubt that p unless p has a content, and it is only by having a prior set of relevant contentful beliefs that one can give this doubt a content. This claim is a natural consequence of the previous discussion on the order of propositional attitude, which says that belief is prior to doubt. Suppose then we form a genuine doubt that p by having a prior set of relevant contentful beliefs, why do we have to appeal to a context of system tied to the world in order to formulate the doubt? Won't it be enough for us to have a set of beliefs, worldy or otherwise, that can help us to determine the content of the proposition being doubted? Here, we need to return to the question, in virtue of what the content of a belief is determined. I have made it clear that both a set of further beliefs and the typical cause of a belief contribute to determining the content of a belief. However, the content-determining role of the typical cause is different from that played by the further relevant beliefs. In order to guarantee that our beliefs are objective, coherence between beliefs does not suffice. What is essential is that those beliefs should be about the external world, i.e., the origin of the content of beliefs is the external world. Thus, if we intend to formulate a doubt that p, we use our language to express this thought. Given that Davidson argues that thought and language are interdependent, it follows that the same content entertained by thought can be expressed by language. To sum up, belief and sentences owe its original content to the external world. 11 Donald Davidson, "Reply to Barry Stroud," in The Philosophy of Donald Davidson, 165. Ju Wang 104 In what follows, I will explore the consequence of Davidson's views about doubt and belief. It seems that what is entailed by Davidson's views in this respect is that doubt can't be wholesale. Here is the reason. In order for S to have a doubt that p, she must identify the content of her doubt that p. However, S can do this only by relating p to other relevant contentful beliefs which she holds; that is to say, S is required to believe for her doubt to take place. Also, since other relevant beliefs are connected to an external world, a doubt is therefore about an external world as well. Here, what S believes is fundamental to what S doubts, so S's doubt presupposes S's belief. The idea that there is a wholesale doubt is simply unintelligible, for a wholesale doubt puts all one's beliefs into question and therefore we can't find any leftover beliefs to determine the content of those propositions being doubted. The result is that the idea of a wholesale doubt simply can't get off the ground. This is so not because of a constraint on our cognitive capability, but rather because the essence of doubt excludes a wholesale doubt. A wholesale doubt is impossible, and thereby doubt must be in its nature local. 4. Consider the ClosureRK Principle Again Recall the ClosureRK principle, and let's take "There's a rabbit in front of me" as p and "I am not a BIV" as q; then an instance of ClosureRK would be as follows: If S has rational grounded knowledge that there is a rabbit in front of me and S competently deduces belief that I am not a BIV via knowledge that there is a rabbit in front of me, then S has rational grounded knowledge that I am not a BIV. Given what I have discussed, I doubt whether this instance is plausible. It fails not because ClosureRK fails, but rather that the instantiation of q is rather dubitable in this case. Specifically, I am wondering whether S could have a belief attitude towards the proposition that I am not a BIV. If not, this proposition would lie beyond the realm of rational knowledge. However, it is still not clear why that I am not a BIV doesn't count as a belief. What is necessary to have a thought? Or more specifically, what does it take to have a belief? Apart from what we have discussed earlier, Davidson maintains that: In order to have a belief, it is necessary to have the concept of belief.12 What is the concept of belief? One may suggest that the concept of a belief is the meaning of the concept 'belief.' In this sense, having the concept of belief is 12 Davidson, "Rational Animals," 104. A Davidsonian Response to Radical Scepticism 105 a precondition to use the word 'belief' in a sentence, which is similar to understanding the meaning of 'desk' before using the word in a sentence. However, this is not what Davidson has in mind. Davidson won't deny that there is a strong relationship between language and thought, so that in order to have a thought such as a belief, S must be able to express that belief in language. But the core idea of what is the concept of a belief is something other than this. We can articulate the concept of a belief, as Davidson later suggests, by referring to the concept of objective truth. Objective truth requires that the truth of a belief is not determined by any of the subject's mental states. Rather, a belief owes its truth partly to the external world. Accordingly, the truth of my belief is not determined merely by my mental states, and it is quite natural to assess my belief in part by reference to how the world is. If a belief is capable of being true or false, correct of incorrect, then to have a belief that p is different from it is true that P. After all, it is always possible that what I believe is not the case. How can we cash out the possibility that my belief could be wrong? Davidson emphasizes that linguistic communication could show command of the contrast between what is believed and what is the case. Further, I contend that the possibility of a thought's being true or false is best illustrated by (i) making sense of the possibility by appealing to relevant beliefs that S holds and (ii) [....] from S's perspective. Why is this move acceptable? The claim (i) is based on Davidson's idea just mentioned. In linguistic communication, when the difference between what is believed and what is the case is revealed, S who finds her prior belief was wrong must be possible to make this wrong belief intelligible, otherwise there cannot be such thing as a recognizable error. This error is intelligible just because S's beliefs in stock can account for such a mistake, and can accommodate a revised new belief. As to claim (ii), why making sense of the possibility has to be from S's perspective? The simple reason is: thought is always someone's thought, thus when attributing thought to someone S, we ought to consider if this thought can be held from S's own light. In other words, we should take into consideration whether S has the network of beliefs to maintain the belief in question. It is for this reason that Davidson remarks: I reserve the word 'concept' for cases where it makes clear sense to speak of a mistake, a mistake not only as seen from an intelligent observer's point of view, but as seen from the creature's point of view.13 Here is a case in point. If I believe that the Lake District is in Scotland, I should be aware that the belief could be wrong. What marks my awareness then? 13 Donald Davidson, Problems of Rationality (Oxford: Clarendon Press, 2004), 9. Ju Wang 106 Is it the claim that my belief could be wrong? Or is it something further that could make the supposed wrong belief intelligible? Awareness of this possibility of being wrong does not bring us any closer to the intelligibility of being wrong, we have to establish a room for the belief to be wrong. How is this room to be built? From my perspective and what Davidson has argued, the room of false belief rests on many other true beliefs. To realize that this belief could be wrong does not require us to find more evidence to support this claim. What is at stake is that it must be possible to make sense of when the belief is regarded as false. My example continues: suppose my belief that the Lake District is in Scotland is wrong (it is actually wrong), its being false would be intelligible for the reason that I had misidentified Lomond National Park, which is instead located in Scotland, as the Lake District, or the reason that I was ignorant of the boundary between Scotland and England, which caused my failure to recognize that the Lake District is a part of England. In this case, my false belief remains possible because it can be explained by other beliefs I still hold, such as that I believe that I had misidentified Lomond National Park as the Lake District, or that I believe that I was unsure where the boundary between Scotland and England lies. The point is that a certain belief's being wrong does not lead to a breakdown in my belief system so that I still have beliefs to which I appeal to account for this possibility. Here, I need to clarify what the breakdown means. When we find a prior belief to be wrong, it is natural for us to explain this situation by appealing to some undoubted beliefs, or a step further, to adjust to this change by changing some beliefs consequently. Changing the epistemic status of a belief, i.e. being true, being false and doubtful etc., may result in a chain of changes in our belief system, and the degree of change is determined by its status in the belief system. What I contend here may sound like a Quinean picture of knowledge,14 but I shall limit my discussion to the content of beliefs only, i.e. what may cause a drastic change in the content of beliefs in the belief system. I would say nothing about adopting or abandoning beliefs for practical reasons or moral reasons.15 To 14 According to Quine, our whole system of scientific claims, or our "web of belief," faces the tribunal of experience as a unity. When encountered with recalcitrant experience, or experience that does not fit our expectations, we could change observation beliefs, meanings of beliefs or even logical laws to accommodate this change. Essentially, nothing in our belief system is immune to revision. However, logical laws or fundamental hypotheses of a theory are so important that any change in them would result in massive changes in our belief system. Restrained by the maxim of minimum mutilation, we tend to avoid drastic changes and make adjustments in other places. 15 For instance, a doctor may, for the patient's benefit, tell her something that isn't true. In this case, a false belief is adopted for practical reasons. Likewise, we tend to think that cheating is A Davidsonian Response to Radical Scepticism 107 summarize, what I mean by breakdown of a belief system is a drastic change in the content of beliefs in the system. The crux is what can cause such a breakdown? In my view, the answer can be easily found in the origin of content of beliefs. Since a belief gets its content from other related beliefs and external causal object, what causes a breakdown in a system must be fundamental commitments in these two aspects, i.e., those about the relations between beliefs and those regarding the external world. The former are logical truths, and the latter are our commitments to the external world or its sceptical counterpart. There is no wonder that a change in logical truth such as declining the law of identity would have a devastating consequence in our belief system. But it is not equally clear what if a change occurs in our commitments to the external world, or to the sceptical scenario for a sceptic. Let's see the following pair: I am a BIV = the sceptical hypothesis does obtain I am not a BIV =the sceptical hypothesis does not obtain From the non-sceptical perspective, we are committed to the sceptical hypothesis not obtaining, i.e., that I am not a BIV. What comes next is a supposed change in this commitment. Our commitment changes to I am a BIV, or that the sceptical hypothesis does obtain. What follows this change? Apparently, our ordinary beliefs regarding the allegedly external object are all changed since the causes of beliefs are only stimuli generated by a supercomputer. It seems that we can still imagine what it is to be a BIV, but there is surely something wrong with this. In normal circumstances, when we talk about "there is a tree in front of me," this belief is caused by and therefore about a tree standing in front of the speaker/believer; while in BIV case, we find it plausible that the same sentence would be caused by and thereby about a series of stimuli regardless of the same subjective perceptual experience. However, what makes our claim about the change of content plausible? It is not that someone had been or is now in the exact sceptical situation, but that some cases we encountered in normal circumstances, like dreams and hallucinations, underlie the plausibility of such claim locally. Nonetheless, the local plausibility does not easily extend to universal, so the sceptical hypotheses usually rest on a thin sense that a sceptical scenario is not a logic contradiction thus it is metaphysically possibility. However, if I have been always a BIV from birth, chances are that I could never see that my beliefs are morally wrong. Even though cheating can bring benefits to an individual at times, given certain moral considerations such as that we should be righteous and we should treat others fairly, we have sufficient moral reasons to abandon the belief that cheating is a good behaviour. The point is that we change beliefs for non-epistemic reasons in everyday life. Ju Wang 108 about stimuli generated by a supercomputer. Even though the supercomputer can bestow me any stimuli needed, my belief can never get content about the computer. What's more, I couldn't have an idea of what the objective world is. Since in order to get the content from the objective world, BIV must be isolated from the supercomputer, otherwise the belief would still be about stimuli rather than worldly objects. It is obvious that by changing our fundamental commitment to the cause of our beliefs, we are committed to change the content of our ordinary beliefs as well. What is crucial now is that, from my perspective, all my previous beliefs would lose their content since they couldn't be about the external world as I earlier presumed. However, I cannot make sense any of the false belief because I have no any contentful beliefs left to which I appeal, thus this possibility of its being false, or the possibility that I am a BIV cannot be genuinely appreciated by me. If I cannot appreciate the possibility of being false, then the original proposition that I am not a BIV does not qualify as a belief at all. It does not count as a belief because no one can appreciate this proposition's being false with determinate content. Interestingly, the case would be likewise if we start from a sceptical hypothesis. If we start with the commitment that I am a BIV, then supposing the possibility that I am not a BIV would also change the content of all beliefs already formed. All my beliefs are about computer stimuli, and none of them is caused by the external world. If I were to form any belief about the external world due to the change of my commitment, I would have to sweep all my previous beliefs and form new basic beliefs from the scratch. Since no any contentful belief remains to help me identify the content of my belief that I am not a BIV, this initial commitment fails to be a belief either. Thus, it seems that no matter what we are committed to at first, whether I am a BIV or not, as far as this commitment leads to a massive change of the content of beliefs, it cannot be a knowledge-apt belief at all. To sum up, in order to have a knowledge-apt belief, we must have the concept of knowledge-apt belief. We can command the concept of knowledge-apt belief by having the concept of objective truth. Objective truth requires that we are aware of and are capable of appreciating the possibility of a belief's being true or false. And this possibility cannot be appreciated unless we have some related contentful beliefs to identity the content of the very belief. Crucially, a change in our fundamental commitment to the cause of beliefs would result in a total change of content in all beliefs, which leaves us no contentful belief at all to make this possibility intelligible. Therefore, it is impossible to appreciate the possibility of our fundamental commitment's being false from our own perspective. It is now A Davidsonian Response to Radical Scepticism 109 clear that our commitment does not meet the requirement of having a belief. And it follows that the sceptical hypothesis does not obtain is not a knowledge-apt belief. Thus, the ClosureRK principle is not applicable to the evaluation of the sceptical hypothesis. 5. Conclusion I have argued that our commitment to the denial of the sceptical hypothesis is not a rational belief; therefore it cannot be applied to the ClosureRK principle. But it is still not clear why sceptics and non-sceptical epistemologists take it as a belief? The therapeutic answer from Davidson is that they both misconceive how a belief can maintain its content while changing its content determining conditions. For sceptics, they wrongly contend that the content of beliefs can be the same while the cause of beliefs changed dramatically and that a universal doubt is a contentful doubt. Therefore, they hold a belief-like attitude towards the proposition that the sceptical hypothesis does not obtain via having other genuine contentful everyday belief. Meanwhile, it is tempting to think that our increased success of attributing ordinary beliefs to others, may serve as a reason to justify that the sceptical hypothesis does not obtain is very likely to be true. However, I am afraid that this idea also goes against Davidson's claim that it is absurd to look for a justifying ground for the totality of beliefs. Our commitment to the cause of beliefs serve as a ground to attribute content to all beliefs, but there is no need to justify this ground since it is in nature outside the reach of any rational beliefs and therefore nonjustifiable. Davidson arrives at the conclusion that doubt is local, and this conclusion echoes Wittgenstein's comment on the structure of reasons. Thus, I would further explore the details between these two diagnoses. Regarding the nature of doubt, Wittgenstein claims: [...] the questions that we raise and our doubts depend upon the fact that some propositions are exempt from doubt, are as it were like hinges on which those turn. That is to say, it belongs to the logic of our scientific investigations that certain things are indeed not doubted. But it isn't that the situation is like this: We just can't investigate everything, and for that reason we are forced to rest content with assumption. If I want the door to turn, the hinges must stay put.16 In this quotation, Wittgenstein maintains that it is only possible to doubt when some propositions are undoubted. Wittgenstein advances his argument from considering the certainty of propositions. Propositions have different degree of 16 Ludwig Wittgenstein, On Certainty, eds. G. E. M. Anscombe and G. H. von Wright, trans. D. Paul an G. E. M. Anscombe (Oxford: Blackwell, 1969), §§341-3. Ju Wang 110 certainties, some of which we are pretty sure while others are not. Thus, propositions with the highest certainty can provide rational support for those which have less certainty, but it is because of the highest certainty that those propositions are groundless. They are groundless because no propositions are more certain to provide rational support for them. What follows is that there can't be rational doubt regarding those hinge propositions on which any rational evaluations take place. In a nutshell, doubt must be local in its nature. Even though Davidson and Wittgenstein arrive at the same conclusion, reasons for the conclusion are different. Davidson draws this conclusion from a consideration on semantic/mental content, i.e., what makes a doubt with a determinate content? In contrast, Wittgenstein focusses upon the epistemic ground of doubt, i.e., what makes a doubt epistemically rational? It is natural to ask whether a contentful doubt is epistemically grounded. Suppose I doubt that this is an orange, I may have plenty of content-determining beliefs that an orange is a round shape fruit, juicy and tastes sweet and sour. Those beliefs can give my doubt a content about an orange rather than a rock. But it is likely that none of these beliefs serves as an epistemic ground to support my doubt. Since to rationally doubt this is an orange, I need to have some evidence like an experienced and reliable farmer told me that it's not an orange. Conversely, an epistemically grounded doubt may not come with a determinate content. If I was informed by an experienced and reliable farmer that this is not an orange, then I can rationally doubt that it is an orange. However, if I don't have belief that an orange is a round shape fruit, juicy and tastes sweet and sour, I may continue believing that this is a round shape fruit, juicy and tastes sweet and sour while maintaining the doubt that this is an orange, which is very implausible. In this case, people would say my doubt is not about an orange since I believe other propositions that fit perfectly with the orange in front of me. One may find it more plausible to argue that the farmer's information is not reliable, or that 'orange' in the farmer's language is not the same as in our language. My point is, if we don't have relevant beliefs to determine the content of a doubt, it would be impossible to appreciate any epistemic support for your doubt. A moral we can draw is that the content requirement of a doubt doesn't coincide with its epistemic support. However, a further question is, in order to rationally doubt something, do we have to have both content and epistemic support in place? If the answer is yes, then Wittgenstein and Davidson could go hand in hand in their respective responses to the closure-based sceptical argument. I suppose here is a reason to answer positively. In order to have a rational doubt, it is not only a matter of having a contentful doubt, but also having a A Davidsonian Response to Radical Scepticism 111 rationally supported doubt. Content of the doubt determines what the subject of the doubt is, and epistemic support for the doubt determines whether the doubt about something is well-motivated. If I aim to have a rational doubt on my friend Weighty's weight, I need to know first what weight is and what Weighty's weight is to be understood. Besides, I also need to know what ground I have in order to doubt Weighty's weight. The first requirement can guarantee that my propositional attitude is really about Weighty's weight rather than Weighty's height or Heighty's weight, while the second requirement can form this propositional attitude as a doubt, rather than believing or wishful thinking. A doubt without determinate content cannot be distinguished from other doubt, and a doubt without a rational support cannot be a doubting attitude at all. Accordingly, those two requirements are not only compatible, but also mutually supported. In this sense, doubt is essentially local both in terms of its content and its epistemic support. Indeed, Wittgenstein and Davidson could have a unified diagnosis of the sceptical illusion that a wholesale doubt is attainable. It is now clear that while the ClosureRK principle is plausible, it does not licence the sceptical conclusion. What is pivotal is that this principle is only applicable to (knowledge-apt) beliefs. Unfortunately, our commitment to the denial of the sceptical hypothesis is not a (knowledge-apt) belief. From a Davidsonian perspective, a (knowledge-apt) belief essentially involves other content-giving beliefs. Commitment to the denial of the sceptical hypothesis is so fundamental that, when being doubted, any contentful beliefs would be discarded therefore. Hence, it will be impossible to take it as a rational, contentful and (knowledge-apt) belief. As a result, we can retain the ClosureRK principle while evading the sceptical challenge apparently posed by this principle.17 17 I am grateful to Duncan Pritchard and Allan Hazlett for helpful discussions. My research is funded by China Scholarship Council and University of Edinburgh.