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Is it Possible to Doubt Everything?

Why is it not possible, if it is not possible, to doubt all things at the same time? Is a life of complete non-belief logically possible: is there a coherent description of Diogenes the Cynic and Cratylus as absolute skeptics? Or must one "have a leg to stand on"?

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

These logic of language ("How is sense distinguished from nonsense in philosophy?") remarks often need further revision and others should be done away with -- because they are wrong (But a few may be right). Time kept in an disordered string.

Topics on this page ...

Words that follow "Query:" led (or misled) Internet searches to this site, and I have responded to a few here.

"Question Everything" (Descartes)

[Note: there is a later and much longer discussion of this topic, with notes about Socrates, Descartes, Augustine, the Apostle Paul, Cato the Elder and Voltaire: Why question everything?]

The night cometh when no man can work.

For a time Samuel Johnson used a dial-plate for his watch with this quotation in Greek. But he set this dial-plate aside, feeling that his watch was too public and therefore pretentious a place for it. (Boswell, The Life of Dr. Johnson, 1768.Ætat.59) The quotation is from the The Gospel according to John 9.4: "I must work the works of him that sent me, while it is day: the night cometh, when no man can work" (King James Version).

Query: question everything. Descartes.

I don't know whether this query was sent to the apt page or not (Search engines are "misdirection engines" in the realm of ideas): it was sent to a story Solzhenitsyn told: "You're a mathematician. What did Descartes say: Question everything." But what did that mean -- everything?

"Question everything." Descartes' project in philosophy was to find something that he could not doubt, and to use that as the foundation on which to build his own system with the same a priori -- i.e. independent of experience of the world -- certainty as, if I recall correctly, the certainty which he believed was possible in mathematics.

It may easily look as if ... secure understanding is only possible if we first doubt everything that can be doubted, and then remove all these doubts. (PI § 87)

But maybe the story from Solzhenitsyn is a bit more in the spirit of Socrates than of Descartes. Because the point of that story is to question all systems. With no exceptions. And Descartes did not question whether the deductive method of certainty of mathematics applies to philosophy and physics as well.

What did Socrates question?

Query: question everything. Socrates.

But note that Socrates' questioning was only in Ethics ("no small matter, but how to live our life"); he used logic as his method or tool, but so do all philosophers (although not with Socrates' originality). He did not ask questions like "How do I know that I am now in Athens and not rather on the moon?" and "How I do I know that I am now awake rather than asleep?" The question "Is it possible to doubt everything?" was not Socrates' question.

Absolute skepticism (Pyrrhonism)

Skepticism is not irrefutable, but palpably senseless if it would doubt where a question cannot be asked. For doubt can only exist where there is a question, and a question only where there is an answer ... (TLP 6.51, tr. Ogden)

And neither a question nor an answer is possible if it cannot be "said" -- i.e. put into words that are not nonsense. But that assertion rests on the TLP's eccentric definition of the words 'sense' and 'senseless' ['nonsense'], and by 'what can be said' it means only: the propositions of natural science. Nonetheless, an assertion of doubt where there are no grounds for doubt, if not meaningless (see next paragraph) is irrational, and if philosophy is rational ... But the raw material of philosophy need not be rational.

We can distinguish -- but remember always, "there are many ways to cut a pie" not just one -- between objective and subjective doubt. By 'objective doubt' we can mean doubt where there are grounds for doubt and criteria for the resolution [or, removal] of the doubt -- resulting in a true or a false proposition. But by 'subjective doubt' we may mean doubt where there are no grounds for doubt, but where there is discomfort, wariness or unease about accepting that a given proposition is true (or, alternately, false) despite there being no reason not to accept it. But then we might also want to say that there is a third category, namely, "philosophical doubt", which consists of drawing a picture, so to speak, e.g. imagining a deity [god] who sees what we cannot see and therefore sees that we are deluded about the truth of this, that or the other proposition.

["If everything speaks for it, nothing against it ..." (OC § 191) -- But isn't that what we call 'certainty' [what everyone means by the word 'certainty']; isn't that what we call 'the absence of grounds for doubt' [cf. TLP [6.51]: "if it would doubt ..."]? Yes, but that was not Wittgenstein-Moore's question: "If everything speaks for .... do I know it?" I.e. is that what we call 'knowledge'? And no it's not: we don't call the absence of grounds for doubt 'knowledge'; knowledge is positive: it requires sufficient grounds, not merely the absence of grounds for doubt (-- I mean the concept 'knowledge' of course).]

"The truth is not determined by taking a vote"

Query: Descartes said a thing is not necessarily true because it is uncontested, not controversial.

I.e. just because no one doubts it ... No, a proposition is not necessarily true just because no one doubts it, but is that the end of the matter? Why does no one doubt it? has to be asked. Is it because no one thinks to doubt it ["community of ideas"] or indeed does not even see a way to doubt it, or because there is no reason [identifiable grounds] to doubt it, and so on. But yes, consensus ["lack of controversy"] is irrelevant to logical necessity (as it also irrelevant to philosophical truth and falsity, although Aristotle had a different view about the place of consensus in philosophy).

The foundations of the moon

Query: why is it not possible for me to doubt that I have never been on the moon?

Many things can be said in response to this query. The following are only a few.

In what context is that "not possible"? You can't -- and this is a remark about the grammar (in Wittgenstein's jargon) of 'doubt' -- just doubt things out of the clear blue sky: a doubt requires a context, just as a statement of fact or any other bit of language does: words are tools that only have meaning in the flow of life: it is what we do with words that gives the words meaning. Cf. 'It's possible that I was on the moon' uttered apropos of nothing. If there is no context, then the query's words 'not possible' mean 'this is undefined language', i.e. nonsense.

What misleads you is that the combination of words is not meaningless, because you know circumstances in which it has a use -- or we could invent a use for it ('logically possible' means 'describable') -- in the language. But, on the other hand, the combination of words is meaningless because this is not one of those circumstances: in the latter case, 'meaningless' = 'a undefined combination of words, in this particular context, not in every imaginable context'; in the former case 'not meaningless' means 'a combination of words with a use or uses in the language'. (Meaning and falsehood.)

Why can't I doubt the truth of the proposition 'I have never been on the moon'? First, rational doubt requires rational grounds for doubt. Here the "cannot" does not mean: I cannot imagine circumstances where I might have grounds for doubt. I can so imagine, but those circumstances do not belong to our normal life, and it is in the context of our normal life that we make use of language. (Cf. "The procedure of putting a lump of cheese on a balance and fixing the price by the turn of the scale would lose its point if it frequently happened for such lumps to suddenly grow or shrink for no obvious reason" (PI § 142). That if is counter-factual, however.)

And second, I cannot doubt that proposition's truth without calling into question the truth of all the other propositions stating my fundamental beliefs about reality (my "world-picture"). They are the foundation of all my thinking about reality; they are bedrock (There are no grounds beneath them). (Foundational propositions. Metaphysics is a "speculative position" -- it is not our normal world-picture, but a critique of it.)

"I cannot doubt that I exist because I must exist if I am to doubt" (Augustine)

Query: is it possible to doubt everything?

I.e. was Descartes wrong -- and if so in what way? Is it indeed impossible to doubt that "If I think, then I exist"? And are there other things that cannot be doubted, if that cannot be doubted, besides that?

"We must work while there is still light." And "questioning everything" (the examined life) is the work that we must do, according to Socrates. It is the path to "knowing oneself".

The difficulty is to put the questions deep enough, to go right down to the foundations of things (CV p. 62), to question everything, taking nothing for granted, if that be possible. That is in any case what philosophers want to do.

Should one philosophize?

Query: why should you question everything?

The discussion of that slogan takes this form: "Question everything!" -- "Why?" -- "Exactly." (And the philosophical form of the query is instead: "Should you question everything?")

Absolute skepticism as a "picture"

Is it possible to "take nothing for granted?" -- For example, not to be unaware of the tools we are using in our questioning, e.g. logic of language's tools for making a distinction between sense and nonsense?

An investigation that tried to investigate everything at the same time would not be what we call an 'investigation' (Is it possible to doubt everything?). We have a picture of Diogenes the Cynic: "I see that the sun is now casting daylight; nonetheless, my eyes may be deceiving me about this, and therefore I will light a candle, although the light this casts may be an illusion as well. I may be dreaming, hallucinating, drunk, or ill. There are so many possible illusions and delusions that it is impossible not to doubt everything." However, when Diogenes says that, is he also doubting the meaning of the language with which he says it, e.g. the application of the names of common objects? Appreciating this objection, there was an absolute skeptic who chose to be silent and henceforth only silently wiggle his finger to indicate that he heard but would not reply. I cannot remember his name; maybe it was Cratylus [cf. Aristotle, Metaphysics 4.1010a]. But how could anyone have come to know the reason for his silence?

ETYMOLOGY: 2. ... Greek etymology ... was involved in sophistic and philosophical speculation on the origin of everything, including, inevitably, language.... Cratylus, pupil of Heraclitus, said that knowledge of Nature's names was required for real speech; without that, utterance was mere noise. Indeed, in his old age, despairing of ascertaining Nature's names, he gave up utterance and used only gestures. (Oxford Classical Dictionary 2nd ed. (1970))

But what are "things" if all things are in flux? If everything is constantly changing and nothing is at rest -- then what are these things that bear "Nature's names"? Plato's response to Heraclitus is to invent the notion of unchanging but imperceptible Forms as the reality behind the changing appearances; these Forms are what bear "Nature's names".

According to what I have called Wittgenstein's logic of language, a gesture belongs just as much to language or convention as any spoken sound or mark on paper does [they are all linguistic signs]. And therefore Cratylus should have simply remained impassive, because a gesture would have meant: "I hear your words, but your words may be mere noise". -- But if all language really is nonsense [undefined noises], then Cratylus's gesture is also nonsense, and if so, then why make it? unless one imagines that it is not nonsense [meaningless].

"The picture is there, but what is its meaning?" (PI §§ 422, 424) Is it useful to philosophy to call a doubt that we refuse to set or accept criteria for the removal of a 'doubt'? Just as objective certainty requires grounds, objective doubt also requires grounds. If we tried to apply the expression 'We can never know' to all cases, would we be saying anything at all? Would that not be like supposing that it is not nonsense to say 'I am here' in any and all circumstances?

"Is it useful?" The question is: what if anything would be the meaning of the absolute skeptic's language? According to Wittgenstein, language gets its meaning from the use the community makes of it as it lives its ways of life; when that language is removed from that way of life, it loses its meaning. [That was the meaning of 'meaning' that Wittgenstein selected, out of the many meanings of 'meaning' available to the philosopher. But there are others, maybe.]

Is my understanding only blindness to my lack of understanding? It often seems so to me. (OC § 418)

That type of disquietude is certainly one of the things that makes someone into a philosopher. (cf. Z § 455)

The picture of the Greek absolute skeptics is not pointless, but its point -- i.e. the meaning of this picture -- is not clear.

The eternal questions without answers as a "way of life"

Would it not be that asking questions about "the riddles of existence" simply belongs to our the human "form of life"? But, according to Wittgenstein, those "questions" are like the various life-guiding "pictures" found in religion (e.g. life after death, the Last Judgment, good as what God commands and evil what He condemns). Such pictures do not state hypotheses; they are not questions that are answerable by an examination of evidence. And so, at least in that respect, questions without answers resemble them. But just try to describe how "absolute skepticism" could be used as a life-guiding picture! Could anyone really live like the Diogenes who lighted his lamp in broad daylight, doubting everything all the time.

A dog is not puzzled by existence. Much less a cat. Such puzzlement simply does not belong to their forms of life -- i.e. such language applied to them is undefined in meaning: what would we mean if we said that a cat was contemplating the morality of killing for sport rather than hunger? or that a dog was pondering life's mysteries? If we could teach a dog to speak, could we teach it to talk about that? [We would not understand a lion if a lion could talk (PI II, xi, p. 223), but if a lion could use language would it then understand us?]

Is it possible to doubt everything? - The Limits of Investigation

... in every investigation there will always be that which is not itself investigated; in every experiment there will be data which are not the result of experiment; in every enquiry there will always be that which is not enquired into. (Drury, The Danger of Words (1973), p. 72)

... a pre?supposition which itself presupposes nothing ... (Copleston, History of Philosophy, Volume VI, XIII, 2)

In every investigation, something is treated as axiomatic. Drury meant: which cannot be investigated because the word 'investigate' would be undefined. E.g. a statement such as 'I doubt that it is possible to remember anything' is nonsense, because it depends of memory and language to even be made (asserted). The limits of memory can -- i.e. this combination of words is defined -- be investigated; one may have one's doubts about the reliability of memory, and experience -- what else -- both confirms and refutes those doubts: but such an investigation depends on memory not being completely unreliable, just as that investigation depends on all language not being meaningless (The limits of sense and nonsense can be investigated, but not if all language is meaningless). Cratylus' position amounts to this: all language may be meaningless ... but that can neither be thought (said to oneself) nor communicated (to others) if all language is meaningless.

Query: what happens to thought when you doubt everything?

If to think is to use language, or, rather, where thinking is to use language, to doubt everything at the same time would be to make rational thinking and deed impossible: that would be what happens to thought.

Query: is it impossible to be skeptical about everything?

There are many levels; maybe -- although Drury argued against this -- one can doubt everything, just not all at the same time. But note, there is a doubt but with that doubt there is a method/technique to remove the doubt. Levels of skepticism. In philosophy: "I am talking about something deeper than that", a deeper skepticism, skepticism about all human knowledge, not a practical skepticism which has limits of sense and nonsense (grounds for doubt and for the removal of doubt) to answer to, but doubt of the ability of man to know anything that is not relative to the human way of knowing (Within the limits of man's nature, man knows many things -- but only within those limits; and so for a dog, a sparrow, a fish, as well). That type of skepticism cannot be resolved, because what there is nothing that we would call a 'resolution' here; it is a question without an answer.

Query: is it possible to doubt that anything at all exists outside the mind?

Descartes held that we can apply "hyperbolical" doubt to the existence of external things, although "he also maintained that reason can overcome this doubt". (Copleston, History of Philosophy, Volume VI, XII, 9)

Doubting everything at the same time would be "hyperbolical" if it were not impossible.

Query: how do we know that things we cannot see both past and present actually exist or existed?

(1) One topic suggested by that query is a question Bertrand Russell asked: "How do you know that the world and all your memories of it did not spring into existence 5 minutes ago?" To give a meaning to that question seems to require the introduction of the picture of a god-like being who sees what man cannot see. (2) A different topic the query may suggest concerns ways of life, or more specifically the human way of life: "How do I know that the history I was taught at school is true or that places I have never been to exist?" The short answer that question is that I don't know. I believe. And the reasons, if there are any, why I believe what I believe vary from type of case to type of case. And where I say 'I' here we might as easily say 'we', although remember that human beings hold a wide variety of conflicting and, in the eyes of some, unwarranted beliefs. (Why do you use the Internet search engine you do? And why do you believe that?)

What do we mean by 'understand'?

Note: this supplements the discussion "Forms of life". (But there is also a later discussion of the concept 'understand' which distinguishes between various senses of 'to understand'.)

Query: how people who are born deaf form their thoughts.

Question: how do we apply the word 'thoughts' to a deaf person? What do we call 'understanding a foreign form of life'? Do we imagine a people who do not use language to think? And if we are deaf ourselves, do we already know the answer to this question? Do we call one thing 'thoughts' for a hearing person, and something else 'thoughts' for a deaf person -- or do we apply that word the same way for all human beings? Does a born-deaf person have thoughts? How are we to answer that question? By examining the verbal testimony of people born deaf (or who became deaf at a very young age like Helen Keller)?

On the grammatical level, you can say we understand -- i.e. the word 'understand' is correctly applied here -- when we talk about 'a deaf person's thoughts', but then we talk about "deeper levels of understanding". One the one hand, it seems presumptuous to deny that anyone but a deaf person can understand what it is to be deaf -- if we mean "understanding on a deeper level"; but on the other hand, the question for logic is about our language's rules of grammar, which are public and the same for everyone. How do I know how people who aren't deaf form their thoughts? (What do I know about anyone else's soul? What I know is our agreement in the language we use [PI § 241].)

We are approaching this question from a logical point of view, not from a scientific one (if there is a scientific approach). -- That is the type of explanation-description that I would want; but someone else might want something very different. What a scientific theory would look like here, I don't know. And we require examples to clarify the meaning -- or to give the expression 'how people form their thoughts' a meaning.

What kind of investigation is the following? "When I am thinking about some question or other, I talk to myself, using the words of our everyday language of course. When deaf persons who have not learned to speak think about some question or other, do they picture the hand gestures of their sign-language to themselves?" That is a possibility. "But how do deaf people who are illiterate think about things?" What do we call 'thinking about things' in the case where language is not used to think? And now this is a grammatical investigation. Wittgenstein cites the case of Mr. Ballard, who is quoted by William James, that he had had thoughts about God before he had learned any language (ibid. §§ 342-349). Is that possible? What do we mean by 'possible' here? (Nothing I can think of.)

Query: physiological location of the mind.

Sent correctly to the Language of Mind (the contrast between our parallel psychological and physiological vocabularies). On the other hand, what harm does it really do if we reply: "the human nervous system"? Doesn't that depend on what consequences are going to be drawn from this identification: e.g. "brain dead" = "soulless"?

Here I remember what Drury, who had to deal with such cases, wrote about "the dependence of mind on body", all the reservations he had which he believed could never be resolved ("The mind and its place in nature"). [Maybe, after Kant, it should be: "Nature and its place in the mind". For a human being: percepts without concepts are blind: imagine the hell-on-earth life would be if you were suddenly robbed of all your concepts: it would mean no higher thought (no, nor even middling thoughts, only thoughts without words). "Nature" itself is a conception. It belongs to the human form of life. Dogs know nothing of "nature", although their lives are lived as a part of it, not as distinct from it, as are our own.]

We have all had the experience of death in life: namely, restful sleep. It would not be strange therefore to regard brain death as a state of permanent sleep -- if the correlations that can be made between sleep and brain death are convincing. But are not mistakes made in science? Yes, of course. After the government of Japan's surrender, the occupation forces distributed DDT to the Japanese people, telling them to pour it over their clothing and also over their bodies to kill lice (One Sunny Day (1996), p. 76). Later scientists learned that DDT may be extremely harmful to human life (It was used in Italy against malarial mosquitos and resulted in many birth defects) -- but that does not mean that the scientists who advocated its use at the time were wrong to do that. They acted, I believe, on the best evidence available to them and with no intention of doing harm. And that is all that any of us can do. However, if we do not do this with the greatest modesty, always aware of the limits of knowing, we are reckless [arrogantly irresponsible].

From the point of view of the logic of language, the combination of words 'physiological location of the mind' is nonsense: the word 'mind' is not the name of an object and 'location' ["location-grammar"] is only applied to objects, and what would 'physiological' contrast with here? But that grammatical remark although correct does not fully respond to this query, which could be restated as: what correlations between physiological phenomena and mental phenomena have been made with respect to locations in the human body? (But if the query really was about "the mind", then it was sent to the correct page.)

Correlations. On the other hand, do you think there must be a correlation in every case between the mind and the brain? Do you imagine that someday scientists will be able to exhume Thomas Jefferson's brain, supposing it to be well-preserved, and say, "Ah, here is the Declaration of Independence; see the words "all men are created equal" ..."

But suppose that someday a machine were invented that could play back the contents of the brain the way a tape recorder can play back recorded speech. Then ... what is to be imagined? It needn't find the words "We hold these truths to be self-evident" but instead a formula which could be read with a protocol (algorithm): If x, get y, etc. until an entire collection of words was assembled. However, where would that collection of words get its meaning from? Would there be a dictionary housed in the human brain ... but such a dictionary would surely have to be very different from the dictionaries we are familiar with, for it would have to fully describe the use of each collection of words found in the brain. For what if the language spoken by the dead man were an unknown language, one for which there were no Rosetta Stone (We would hear the sound, but not know its meaning [the Stoics' lekton]). And so even if such a machine were invented, the question of what gives that collection of bare signs their meaning would remain. And a mechanical solution to answering that question has yet to be invented or perhaps SO far even imagined ("The limit of science -- is concept-formation"; cf. the limits of Internet search engines). But even such a machine would not do, because even collections of words are not always used according to strict rules, and furthermore new thoughts occur to us: now where do those thoughts come from and where are they stored, supposing that they are stored, and how is their meaning to be determined? (It's a difficult picture to construct (try to imagine).)

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