Skip to content
BY 4.0 license Open Access Published by De Gruyter March 14, 2022

Does Doubt Require Reasons?

  • Christoph C. Pfisterer EMAIL logo
From the journal Wittgenstein-Studien


In On Certainty, Wittgenstein conceives a novel way of dispelling skeptical doubts about our knowledge of the external world. He acknowledges that in his attempt to refute the skeptic, Moore uncovered epistemologically relevant propositions such as ‘I know that this is a hand’. But he denies that appealing to such truisms is likely to succeed in refuting skepticism–not because they cannot be doubted, but because they are not objects of knowledge in the first place. Rather than refuting skepticism about the external world, Moore’s truisms form the background against which claims to knowledge and doubt are reasonable, meaningful, or justified. By incorporating such conditions for doubt, Wittgenstein seems to provide an effective rationale against skepticism: not only do we lack reasons for certain doubts about our knowledge of the external world, but those doubts also presuppose that much of what we take to know is exempt from them. This paper critically examines the claim that doubt requires reasons and uses Descartes’ famous dream argument as an example to show that not every doubt can be easily dispelled by invoking it.

1 Introduction

This paper aims not so much to find a conclusive answer to the question of whether doubt requires reasons as to question what might follow from an affirmative answer. For if one can only doubt if there is a reason or occasion for doubt or distrust, as Wittgenstein seems to suggest, then doubts that do not meet this condition can be easily dispelled. Doubts without justification would be no threat, just as knowledge without justification gives no comfort. But can deliberate or persistent skeptics be put in their place when they are reminded of the condition that doubt requires reasons? I believe that it is anything but clear what might follow from such a demand.

One must, of course, take note of the fact that Wittgenstein is, at least prima facie, quite decisive on this issue. For example, at the beginning of On Certainty, he emphatically rejects the question of whether I can doubt that I have a brain: “Grounds for doubt are lacking!” (OC 4). Other passages, which will be discussed later, seem to confirm the view that doubt requires reasons (OC 122, 323, 458, 519). Furthermore, Wittgenstein is known to have taken a critical stance towards skepticism very early on:

Scepticism is not irrefutable, but obviously nonsensical, when it tries to raise doubts where no questions can be asked. For doubt can exist only where a question exists, a question only where an answer exists, and an answer only where something can be said. (TLP 6.51)

Already here, our attention is drawn to the conditions for raising doubts, if these are meant to be more than pure nonsense. However, Wittgenstein is also known to be a thinker who has constantly developed his views. To avoid reading something into his later work that he may no longer hold so resolutely, this early passage should not be used as evidence that, according to the later Wittgenstein, doubt always requires reasons.

As far as knowledge is concerned, the requirement for justification is comparatively uncontroversial, be it because one follows Austin (1946) in thinking that knowledge claims are typically bolstered by answering the question ‘How do you know?’ or because one holds the orthodox view that knowledge is justified true belief.[1] But with the requirement that one must also have reasons to doubt, doubt is aligned with knowledge in a way that could raise false hopes about how doubts can be dispelled. This doesn’t mean that doubters cannot be made accountable as a matter of principle, but as a general strategy for defending knowledge against skeptical doubts, tu quoque is not enough. Skeptical doubts cannot simply be eliminated by inviting the skeptic to think about whether their doubts have a reasonable foundation. For one thing, skeptical doubts can be well-founded, as the example of Descartes’ methodological doubt shows. For another, the skeptical threat might persist, as it seems, even if there are no reasons to doubt what we claim to know.

The paper is structured as follows. In section 2, I roughly sketch the positions of Wittgenstein’s interlocutors by presenting Descartes’ dream argument and Moore’s proof of the external world. In section 3, I attempt to explain the nature of the skeptical threat by drawing on the work of Barry Stroud. In section 4, I discuss how Wittgenstein enters the debate between Moore and Descartes by breaking with the traditional opposition between knowledge and doubt. Finally, in section 5, I articulate my reservations about the idea that requiring reasons for doubt is an effective remedy against the skeptical threat.

2 Descartes Dream and Moore’s Proof

For the purposes of stage-setting, I shall briefly introduce two antagonists, Descartes and Moore, who significantly shape Wittgenstein’s discussion in On Certainty. This is to provide a better understanding of the skeptical threat posed by Descartes and to help identify the shortcomings that Wittgenstein finds in Moore’s response. But before presenting the two positions, I want to start with some general remarks about the resilience of the theses in the source text.

Unlike the Tractatus and the Philosophical Investigations, On Certainty is not work that lives up to Wittgenstein’s standards. On the surface, we are also dealing with a collection of consecutively numbered passages. But despite their “thematic unity which makes them almost unique in Wittgenstein’s whole literary output” (Wright 1972, 47), many of these paragraphs have the character of notes or drafts that Wittgenstein would presumably have revised had they not been written in the last two years of his life. For example, remarks are often prefaced with statements that suggest a certain dissatisfaction with his own writing: “I should like to say” (OC 69, 151), “I want to say” (OC 111, 124, 401, 404, 447, 448, 450, 457, 509), or “I am inclined to say” (OC 437). Other passages contain explicit disclaimers: “And of course that is wrongly put” (OC 303), “That is very badly expressed and probably badly thought as well” (OC 358), “Here there is still a big gap in my thinking. And I doubt whether it will be filled now” (OC 470). Elsewhere Wittgenstein even confesses: “I do philosophy now like an old woman who is always mislaying something and having to look for it again: now her spectacles, now her keys” (OC 532). This doesn’t sound like a philosopher who feels confident, and one should keep this fact in mind when trying to take lessons from On Certainty (cf. Schroeder, forthcoming).

Wittgenstein’s arguments and theses are not quite as settled as those in some of his other works. As interpreters, we are challenged to keep an eye on the big picture and to actively participate in Wittgenstein’s thinking. This is precisely what Wittgenstein demands when he alludes to the reader’s personal contribution when dealing with his ‘notes’: “I believe it might interest a philosopher, one who can think himself, to read my notes. For even if I have hit the mark only rarely, he would recognize what targets I had been ceaselessly aiming at” (OC 387).

One clear target is Moore’s proof for the existence of objects in the external world, which is the linchpin of Wittgenstein’s reasoning. G.E. Moore famously argued that the existence of external things can be proved by the following procedure:

By holding up my two hands, and saying, as I make a certain gesture with the right hand “Here is one hand,” and adding, as I make a certain gesture with the left, “and here is another.” (Moore 1939, 144)

Moore was confident that such a procedure satisfies all the criteria for rigorous proof: the premises are known to be true, the conclusion that at least two things exist in the external world follows from the premises, and it is distinct from them (hence no petitio principii). Moore is occasionally charged that it is unclear whether his proof is directed against idealism or skepticism. Does Moore compete against someone who denies the existence of things in the external world, or someone who denies our knowledge of them? Moore presumably thought he could kill two birds with one stone, and assuming a factive notion of knowledge this is not implausible. For if we know or can prove that at least two external objects exist independently of our mind, this refutes not only skepticism, which denies knowledge of such facts, but also idealism or immaterialism, which denies these facts themselves. I will focus on skepticism, even though for Wittgenstein and Moore the main target was idealism (cf. Glock 2004, 66).

This brings us to the second, albeit imaginary, antagonist in Wittgenstein’s On Certainty. Descartes, in his search for absolute certainty, famously considers that what he experiences sitting by the fire with a piece of paper in his hands might just all be a dream. The so-called ‘dream argument’ represents the second stage of skeptical doubt and is put forward right after raising doubts against sense perception in the first meditation. Descartes does not claim that the senses could always deceive us, but rather that it is not ‘prudent’ to rely on something that has deceived us even once. He considers the objection that to deny that he is sitting by the fire holding a piece of paper in his hands would put him in the category of madmen who believe that they are pumpkins or made of glass. Descartes dismisses the objection, however, since one need not be crazy or insane to doubt what one immediately experiences, as one may simply be asleep and dreaming. He says that asleep at night, one can be convinced of just such familiar events as that one is sitting by the fire when in fact one is lying bed:

Yet at the moment my eyes are certainly wide awake when I look at this piece of paper; I shake my head and it is not asleep; as I stretch out and feel my hand I do so deliberately, and I know what I am doing. All this would not happen with such distinctness to someone asleep. Indeed! As if I did not remember other occasions when I have been tricked by exactly similar thoughts while asleep! As I think about this more carefully, I see plainly that there are never any sure signs by means of which being awake can be distinguished from being asleep. The result is that I begin to feel dazed, and this very feeling only reinforces the notion that I may be asleep. (Descartes 1996, I, 19)

The dream argument seems to undermine empirical knowledge completely. For if I can legitimately claim to know something only if I can rule out that I am just dreaming what I say I know, then any claim to knowledge would have to be made with a kind of ‘anti-dream warrant’. I would have to have a test, so to speak, that I am not dreaming right now, and it would have to be beyond doubt that I am not just dreaming to pass that test (cf. Stroud 1984, 20 – 22).

3 The Nature of the Skeptical Threat

Before turning to Wittgenstein’s response to Moore and Descartes, I want to dwell on the dream argument and address a misunderstanding that affects not only the concept of knowledge but also the skeptical challenge to knowledge. Given the required evidence about one’s waking state, one might argue that Descartes sets the bar too high. According to Descartes’ standards, it is not enough that I know that I am sitting by the fire holding a piece of paper in my hands; I must also know that I am not dreaming this. Descartes seems to have an overly demanding concept of knowledge, one according to which knowing that p presupposes knowing that one knows that p. Why not accuse Descartes of having changed the concept of knowledge in a way that makes it impossible for anyone to know anything at any time?

Barry Stroud (1984, 40) answers this objection with the following comparison. Suppose that someone claims that there are no physicians in the city of New York. Such an outrageous claim would be hard to reconcile with what we believe applies to cities of this size. But now this person explains that there is in fact no physician in New York, because by ‘physician’ he understands a person who has a medical degree and can cure any conceivable illness in less than two minutes. The question is whether Descartes alters the meaning of the term ‘knowledge’ in the same way as someone who imposes conditions on the correct use of ‘physician’ that can hardly be met. Stroud argues that Descartes cannot be accused of redefining the concept knowledge, since he only finds that there is no reliable test to find out whether I am awake or dreaming. The skeptical threat to my knowledge has not been disarmed, because if it turns out that I am indeed dreaming, then it is simply not true that I know that I am sitting by the fire with a piece of paper in my hands—and this does not depend on some peculiar conception of knowledge.

A dreaming person certainly does not meet the conditions for knowledge, even if things happen to be as they appear in the dream. But does a person who is only possibly dreaming meet the conditions for knowledge? After all, we attribute knowledge in everyday situations without asking people to test for the possibility that they are dreaming. Stroud questions whether resorting to the practice of attributing knowledge can do much to counter the skeptical challenge as put forward by Descartes. As a person who cannot rule out the possibility of dreaming, I may still be said to know that p, but being said to know that p is a weaker condition, much easier to fulfill than Descartes’ condition of knowing that I know that p. This does not mean that our knowledge attributions are inappropriate or unjustified unless the outrageous possibility of dreaming has been excluded—in fact, it is only reasonable not to exclude every conceivable possibility of doubt. But as reasonable as such omission is, it fails to fill the gap between meeting the conditions of saying that one knows, on the one hand, and meeting the conditions of knowledge, on the other hand (cf. Stroud 1984, 64). The skeptical threat posed by Descartes’ dream argument is aimed at the latter and does not depend on whether the meaning of ‘know’, like that of ‘physician’, has been changed in fatal ways.[2]

Stroud characterizes the nature of the skeptical threat to the everyday concept of knowledge with a story by Thompson Clarke (1972, 759). So-called ‘plane-spotters’ have the task of reliably identifying aircraft based on distinguishing features. They learn from their manuals that a plane is type F if it has the features x, y, and z, and that it is type E if it has the features x, y, and w. Fully trained plane-spotters will not say of any plane that it is an F, unless they have recognized all three features x, y, and z, and they can distinguish F-type aircraft from E-type aircraft because of their training (cf. Stroud 1984, 67). Unfortunately, there are also aircraft of type G with the same features as aircraft of type F, but this piece of information is withheld from the plane-spotters, because aircraft of this type are extremely rare. The question is whether, under these circumstances, a trained plane-spotter can know that a plane is of type F if it has the features, x, y, and z.

One lesson to be learned from this story is that if we are in the same predicament with our everyday knowledge claims as the plane-spotters are, it is not because the concept of knowledge has been undermined in any way. The plane-spotters can still do their job and distinguish type F and type E aircraft because they know their characteristic features. What is undermined, however, is the claim to know, given an aircraft with characteristics x, y, and z, that it is of type F when it could just as well be of type G. By the same token, my claim to know that I am sitting by the fire with a piece of paper in my hands is undermined by the mere possibility that I could just as well be lying in bed dreaming. We cannot cite any fact to the effect that we know what we think we know, once there is a possibility of dreaming, although epistemically we are not at fault, and regardless of this possibility continue to speak of knowledge. The skeptical threat arises solely from this possibility, which I cannot rule out in a given situation, and does not depend on everything being dreamed, no aircraft being identified, or the meanings of expressions being manipulated.[3]

4 Wittgenstein on Knowledge and Doubt

Taking stock, we have Descartes’ skeptical doubts on one side and Moore’s proof on the other. Wittgenstein now enters the dispute between the skeptic and Moore with a “three-cornered argument” (Kenny 1973/2006, 161). He makes concessions on both sides and offers criticism, again on both sides, and in ways that are sometimes surprising rather than immediately convincing. These circumstances make it difficult to identify Wittgenstein’s position with any degree of confidence, but I shall try to tease it out all the same, if only in broad outline.

Wittgenstein sympathizes with Moore’s effort to confront the skeptic with such homespun propositions as ‘Here is one hand’, ‘The earth existed for a long time before my birth’, and ‘I have never been far from the earth’s surface’, but denies that the knowledge claims associated with such propositions can be a direct answer to the skeptic. Recall that Moore wants to be on par with the skeptic when he says that he knows very well that he has hands, etc. It was clear to Wittgenstein that affirmations of this kind do not make any impression on the skeptic: “Moore’s mistake lies in this—countering the assertion that one cannot know that, by saying ‘I do know it’” (OC 521). Moore’s proof seems downright dogmatic, since what needs to be proved is presupposed as exempt from doubt. Why should the sight of his own hands warrant the existence of material objects when Moore could just as well be mistaken about the existence of his hands? This is the beginning of Wittgenstein’s investigation:

If you do know that here is one hand, we’ll grant you all the rest. When one says that such and such a proposition can’t be proved, of course that does not mean that it can’t be derived from other propositions; any proposition can be derived from other ones. But they may be no more certain than it is itself. (OC 1)

Wittgenstein doesn’t level formal criticism against Moore—he is prepared to accept whatever follows from the premises, provided that Moore can be said to know that here is one hand. The second remark suggests that while the desired conclusion can be derived from Moore’s (or other) premises, one would accept this derivation as proof only if the premises are “more certain than the conclusion” (Child 2011, 193). This condition is not met by Moore’s proof, though Wittgenstein would presumably not be satisfied even if Moore had come up with a proposition more certain than the conclusion. For a recurring theme in On Certainty concerns precisely such ‘Moorean propositions’ and the question of whether they can be associated with knowledge claims at all. ‘I know that this is a hand’ is a statement which, apart from very specific circumstances, we would not consider to be a meaningful contribution to a conversation.

Now, can one enumerate what one knows (like Moore)? Straight off like that, I believe not. – For otherwise the expression “I know” gets misused. And through this misuse a queer and extremely important mental state seems to be revealed. (OC 6; see also 58)

Moore’s proof fails, according to Wittgenstein, with the very first premise, because it incorrectly says of something that it can be known. This finding is reminiscent of Wittgenstein’s considerations regarding the possibility of a private language in the Philosophical Investigations. There, Wittgenstein claims that one cannot know that one is in pain, since one’s own pain is not an ‘object’ of knowledge, so to speak. This may be equally surprising, as one would have expected to know at least about one’s own feelings: “only I can know whether I am really in pain; another person can only surmise it” (PI 246).

Wittgenstein immediately rejects this hypothesis: “In one way this is false, and in another nonsense” (ibid.). His dyadic diagnosis is based exclusively on the concept of knowledge, and this makes it relevant in the present context. On the one hand, it is simply not true that others cannot know if I am in pain, provided one adheres to the ordinary use of the word ‘know’. For example, when I writhe in pain or tell others that I am in severe pain, those who are watching or listening to me know very well that I am in pain. On the other hand, it is nonsensical to claim that I know I am in pain, since such knowledge would presuppose the possibility of error and doubt. But how could I possibly be wrong about my pain? I cannot even drive a wedge between the fact that I am in pain and my knowledge of that fact—if it seems to me that I have a toothache, then I have a toothache. According to Wittgenstein, one cannot say of me at all that I know I am in pain, since this would at best be taken as reporting that I am in pain, no matter what I know. By way of conclusion, he explains that it equally only “makes sense to say about other people that they doubt whether I am in pain, but not to say it about myself” (PI 246). With respect to pain and other sensations, we can thus speak of ‘knowledge’ in a meaningful way only when it is about the sensations of others, precisely because the possibility of being wrong is not excluded in principle (PI, xi, 310).[4] For this reason, one cannot say that one suspects or wonders whether one is in pain either.

Wittgenstein’s comparison between the two sentences ‘sensations are private’ and ‘one plays patience by oneself’ (PI 248) is to be understood against this background. Sensations are not private in the special sense that one has privileged access to one’s own sensations. Rather, it is part of the concept of sensation that one cannot be wrong about one’s own sensations, just as it is part of patience that one cannot play it two by two. It is a “grammatical proposition” that sensations are private, since it establishes the rules for speaking about sensations, rather than being itself an empirical proposition the truth of which can be determined (PI 251).

But how does this relate to Moore’s propositions? That I have hands and that the earth existed long before I was born are, after all, empirical propositions (or like empirical propositions).[5] First, as empirically used propositions, their negation does not amount to nonsense (cf. Glock 2004, 72), and, second, they are based on (proprioceptive) experience. I can feel and see my hands, and because I have done so many times, I do not need to check again to know that I have hands (cf. Schroeder forthcoming). Moorean propositions can be false, but their falsity in no way fits with the things we believe (cf. Glock 1996, 78).

Wittgenstein makes use of various images and comparisons to explain how Moorean propositions express fundamental certainties the denial of which would mean radical changes in our conceptual system; e. g. the so-called ‘river-bed’ metaphor (OC 97 – 9), ‘hinges’ (OC 341, 343, 655), and comparisons with mathematical propositions (OC 447 – 8, 455, 651 – 8). Scholars disagree about the status Wittgenstein ultimately assigns to Moorean propositions and about whether Moorean certainty can be traced back to individual propositions at all. I will not choose between the competing readings here and instead just take the rationale we find in Wittgenstein’s private language argument: Moorean propositions cannot be known because, like propositions about one’s own pain, they are not open to error and doubt, as is the case with ordinary empirical propositions.[6]

Thus, empirical knowledge presupposes that one can meaningfully deny what one claims to know. With this conception of knowledge, Wittgenstein not only attacks the first premise of Moore’s proof, but also the conception of knowledge endorsed by Descartes. For Descartes is looking for something that we can know with absolute certainty and cannot possibly doubt. To do this, he uses a kind of subtractive method that eliminates all candidate propositions failing his tests, finally finding some proposition that (in his view) is impossible to doubt. Moore follows Descartes insofar as he presents a whole list of propositions that one cannot doubt and therefore knows. Wittgenstein, on the other hand, breaks with the Cartesian tradition when he states that empirical knowledge presupposes the possibility of doubt.

In a way, Wittgenstein breaks with the Cartesian tradition twice, since he cuts the conceptual connection between the impossibility of doubt, on the one hand, and empirical knowledge, on the other, altogether. While Descartes and Moore assume that knowledge follows from indubitability, Wittgenstein seems to deny any entailment between indubitability and knowledge: (i) from the fact that I cannot doubt that p, it does not follow that I know that p; and (ii) from the fact I know that p, it does not follow that I cannot doubt that p. Both theses would have to be substantiated and discussed at length; so far, I have mainly discussed (ii), which I believe is supported by Wittgenstein’s reflections about the possibility of a private language and the misguided conception of referring to sensations. But just as (ii) is clearly directed against Moorean certainties, so (i) breaks even more strongly with traditional epistemology by questioning the Cartesian conception of knowledge as depending on the discovery of undeniable truths.

5 The Promise of Common Ground

Finally, I want to address the question of whether Wittgenstein’s break with tradition can save us from the classical problem associated with the concept of knowledge. How can Wittgenstein respond to the skeptical challenge if he denies the traditional opposition of knowledge and doubt? I will just briefly touch on one specific answer that seems to be a long shot. It is not promising to try and beat the skeptic at their own game by pointing out that even doubts must be justified, rational, or based on common ground. Notorious passages in On Certainty seem to suggest exactly this strategy:

If you tried to doubt everything you would not get as far as doubting anything. The game of doubting itself presupposes certainty. (OC 115)

That is to say, the questions that we raise and our doubts depend on the fact that some propositions are exempt from doubt, are as it were like hinges on which those turn. (OC 341)

The second remark, as is well known, is the one that has put the label ‘hinge proposition’ on the map, and its interpretation remains controversial among experts. Regardless of how one understands Wittgenstein’s comparison with hinges, on which even doubts are said to depend, I believe it doesn’t settle the issue about skeptical doubts. In posing the skeptical threat, Descartes may have to rely on the same framework of certainties against which we justify our claims to knowledge. However, it doesn’t follow from such a constraint that we don’t understand what is meant by asking whether we can rule out the possibility that we are not dreaming right now. The skeptic’s use of the words ‘knowledge’ and ‘dream’ does not deviate in any way from how we would use these expressions: We would not attribute knowledge of things in the external world to a dreaming person any more than we would attribute knowledge of aircraft type F to a plane-spotter.

To be sure, the point is not to deny that Wittgenstein is right to remind us that “[d]oubt itself rests only on what is beyond doubt” (OC 519). But when it comes to averting the skeptical threat, the potential of the fact that we share with the skeptic a common ground that is beyond doubt must not be overstated. By raising the possibility of a dream, one doesn’t gloss over anything beyond doubt, nor does one undermine the common ground for meaningful conversation. The tendency to overestimate the potential of a common ground seems to be due to the lack of a proper understanding of the skeptical threat rather than Wittgenstein’s lack of sensitivity to the matter. For example, the skeptical threat is sometimes misconstrued as the possibility of life being one big dream (cf. Stroll 2009). Such a radical hypothesis will be rightly rejected by asking for the meaningful basis or the reasons for doubt. Apart from the fact that Descartes could have given a reason for radical doubt, if only a methodological one, the skeptical threat as presented here does not imply any violation of intelligibility. The question of reasons for doubt may pull the rug out from under the feet of the radical skeptic who doubts that anything can ever be known. But it does not contribute much to my defense that I am not dreaming right now, or to dispelling any similar possibility that is incompatible with my claim to knowledge.

By way of conclusion, I suggest taking a closer look at those passages that are often cited as evidence for Wittgenstein’s dictum that doubt requires reasons. Remarkably, this thought is not introduced as a direct rebuttal against the skeptic simply because of its linguistic form. Mostly, Wittgenstein only asks whether doubt requires reasons, or he formulates the thesis in the context of a question:

Can one say: “Where there is no doubt there is no knowledge either”? Doesn’t one need grounds for doubt? (OC 121 – 2)

So rational suspicion must have grounds? (OC 323)

One doubts on specific grounds. The question is this: how is doubt introduced into the language-game? (OC 458)

Of course, this finding does not allow for any firm conclusions, since every thesis or agreement with a thesis can be formulated as a question, right? But would Wittgenstein not have advocated this thesis with more verve if he had thought that it could dispel skeptical doubts?

This brings us directly to the passage quoted at the beginning of this article, where Wittgenstein addresses the question of whether one can doubt a sentence like ‘I know that I have a brain’. There we find it loud and clear: “Grounds for doubt are lacking!” (OC 4). However, the fact that Wittgenstein uses an exclamation mark is not proof that he expects this response to be an ultimate answer to the skeptic, as he usually doesn’t shout out what he thinks is right and important. The exclamation mark could simply represent the tone of the response to such an outrageous question without emphasizing approval that this refutes the skeptic, to whom Wittgenstein immediately gives the floor: “Nevertheless it is imaginable that my skull turn out empty when it was operated on” (ibid.). To reiterate, the claim is not to dispute Wittgenstein’s dictum that doubt requires reasons or undermine its importance in his discussion of the nature of knowledge. Rather, my contention is that Wittgenstein had no illusions regarding the anti-skeptical promise of salvation in the dictum that doubt requires reasons. Anything else would be astonishing from a philosopher who, unlike pretty much everyone else, establishes a direct connection between the concept of empirical knowledge, on the one hand, and what can be meaningfully doubted, on the other.[7]


Austin, John L.: Other Minds, in: Urmson, James O. & Geoffrey J. Warnock (eds.), Philosophical Papers, Oxford 1946, 76 – 116.10.1093/019283021X.003.0004Search in Google Scholar

Child, William: Wittgenstein, London 2011.10.4324/9780203817759Search in Google Scholar

Clarke, Thompson: The Legacy of Skepticism, in: Journal of Philosophy 69.20 (1972), 754 – 769.10.2307/2024672Search in Google Scholar

Descartes, René: Meditations on First Philosophy, ed. by John Cottingham. Cambridge 1996.10.1017/CBO9780511805028Search in Google Scholar

Glock, Hans-Johann: Stroud’s Defence of Cartesian Scepticism – A ‘Linguistic’ Response, in: Philosophical Investigations 13.1 (1990), 44 – 64.10.1111/j.1467-9205.1990.tb00066.xSearch in Google Scholar

Glock, Hans-Johann: A Wittgenstein Dictionary, Cambridge, Mass. 1996.10.1111/b.9780631185376.1996.00022.xSearch in Google Scholar

Glock, Hans-Johann: Knowledge, Certainty and Scepticism: In Moore’s Defence, in: Danièle Moyal-Sharrock (ed.), The Third Wittgenstein. Aldershot 2004, 63 – 78.10.4324/9781315236810-4Search in Google Scholar

Kenny, Anthony: Wittgenstein, Rev. ed. 1973/2006.10.1002/9780470776643Search in Google Scholar

Moore, George Edward: Proof of an External World”, in: Proceedings of the British Academy 25.5 (1939), 273 – 300. Reprinted in: Philosophical Papers, New York 1966.Search in Google Scholar

Stroud, Barry: The Significance of Philosophical Scepticism, New York 1984.10.1093/0198247613.001.0001Search in Google Scholar

Schroeder, Severin (forthcoming): Farewell to Hinge Propositions, in: Christoph C. Pfisterer, N. Rathgeb & E. Schmidt (eds.), Beyond Wittgenstein: Language, Mind, and Normativity, London.Search in Google Scholar

Stroll, Avrum: Wittgenstein and the Dream Hypothesis, in: Philosophia 37 (2009), 681 – 690.10.1007/s11406-009-9193-5Search in Google Scholar

Wright, Georg Henrik von: Wittgenstein on Certainty, in: Problems in the Theory of Knowledge, The Hague 1972, 47 – 60.10.1007/978-94-010-2764-9_6Search in Google Scholar

Published Online: 2022-03-14
Published in Print: 2022-03-14

© 2022 Walter de Gruyter GmbH, Berlin/Boston

This work is licensed under the Creative Commons Attribution 4.0 International License.

Downloaded on 27.2.2024 from
Scroll to top button