I read a lot about people saying that it is impossible to be certain about anything with 100% certainty, but that means that this rule in and of itself must be true 100%.

I mean the rule that "we cannot be certain about anything" must itself be certain, which breaks the rule. So in order for this rule to be applied it needs to be broken at least once which is for itself.

This circular reasoning makes it hard for me to grasp.

Also some people divided the things that we can know for certain and the things we cannot (e.g functional certainty: I am certain I am writing this, not sure how, but certain it's happening), but even that has been doubted and counter arguments where proposed to refute it. So how exactly do we interpret this? Does it mean that this rule simply isn't all around true and that we can know somethings with absolute certainty?


100% doesn't mean a numerical representation that is mathematically practical, it just means "absolute"

  • 1
    Statements like "we can not be 100% certain" have no numerical "value" of certainty attached to them, nor does it make sense, there is no meaningful sample space. The "100%" in the sentence does not mean anything more than a superlative for practical confidence. Since the "rule" is not meant in an abstract generalistic sense it can not be applied to itself, and even if it is, it means nothing more than "I am pretty sure". Sometimes it is even jokingly stated as:"There is only one thing that is 100% certain, that nothing else is 100% certain".
    – Conifold
    Mar 7 '19 at 23:47
  • Humility, and pragmatc skepticism are cornerstones of real learning. If you believe anything with abdolute certainty then how can you change your mind? And if you can't change your mind, how can you learn? It's just easier to keep an open mind. I'm 'pretty sure' that the sun will rise tomorrow though.
    – Richard
    Mar 7 '19 at 23:52
  • There are knowns and there are unknowns, but then there are known unknowns and unknown unknowns. When you are certain of something, are you automatically certain you are certain of it? If I am uncertain that I am certain, is that certainty? If not, I can be certain of something, but uncertain that I am certain. If you are at least uncertain about the certainty of everything you know, then you have not created a contradiction by being certain that you are not truly certain of anything.
    – user9166
    Mar 9 '19 at 1:30
  • @Conifold you can replace that 100% with absolute, I am not trying to quantify certainty, I am trying to assert the statement of "we can never be certain about anything"
    – engma
    Mar 9 '19 at 3:12
  • @Richard Being humble and pragmatic is good in the scientific research realm, where we look at the "how" or the "actuality" or "essence" of the object under test, but I am talking about being certain that this thing "exists", not discussing it's "form" but the fact that it is "truthful" or "real" like me and you, not discussing our "form" of existence, just that it is, leaving an open mind for the actuality of it
    – engma
    Mar 9 '19 at 3:14


'Nothing is certain' is a proposition. If it is true, then no proposition is immune from error. But that's problematic since 'Nothing is certain' is a proposition which refutingly applies to itself.

No paradox

Our being certain of anything is a propositional attitude, not itself a proposition. It is the attitude towards a proposition of believing it to be immune from error. In the present case it is the propositional attitude of believing that no proposition is immune from error. I don't think that refers back to the attitude itself, since (as said) an attitude is not a proposition. Believing can't be immune from or vulnerable to error since it is a merely a psychological phenomenon which obtains or doesn't. Of course, what we believe can be immune from or vulnerable to error. The former in principle, the latter all too common.


The point isn't (to respond to another answer) that we can't be 100% certain - absolutely certain, though the '100%' logically adds nothing to 'certain' any more than my 'absolutely' does. Rather, ask yourself what sense does it make to say that we are 99.37% certain or 55% certain? Certainty is a condition we're either in or out of - we can't be in it to a numerically determinate degree (<100%).

  • So from that we deduce that certainty is subjective and not objective?
    – engma
    Mar 10 '19 at 21:43
  • I am also not sure I understand what you mean by "propositional attitude", just in terms of usability? if it's an "attitude" then it has limited usability and will be mostly in terms of being an incentive to continue researching in science, but for example not very useful in terms of criminal indictment, otherwise every criminal would go free, right?
    – engma
    Mar 10 '19 at 22:44
  • Geoffrey, if I may ask: why does anyone insist that the proposition is a paradox rather than a hasty expression?
    – user38026
    Sep 9 '19 at 12:46

It is useful to distinguish truth from certainty: specifically, a statement being true and a person being certain about the statement. For instance, it might be true that there is an odd number of fish in the ocean right now but perhaps I cannot be certain of this. So, some things may be true even though we cannot be certain that they are true.

The same goes for the 'rule' you mention. It might be true even though we cannot be certain of it. The rule also applies to itself: it says that we cannot be certain about it. That is perfectly consistent, as, again, it is possible for a statement to be true and for us to not be certain of it.

What may seem nonetheless problematic about this rule is that it might be interpreted to say that we shouldn't believe it. But that depends on what exactly it means by 'certainty'. If it's certainty as in a subjective probability of 1, it might be true but uninteresting: we'll do fine with being almost-certain. And we could be almost-certain about the rule itself, as it doesn't preclude that. But if by 'certainty' it simply means high probability (not just 1), in the sense that we cannot be sure to any degree of anything, then it does undermine itself: if it's true we shouldn't believe it.


I mean the rule that "we cannot be certain about anything" must itself be certain, which breaks the rule. So in order for this rule to be applied it needs to be broken at least once which is for itself.

Certainty is immeasurable. A person is certain about something which he considers indisputable, true. Certainty is not a characteristic of a thing, but rather a mindset of someone who perceives that thing.

I wouldn't consider that "truism" a rule, nor a maxim, nor an axiom. Where is its proof? It is a meaningless good-sounding phrase.

  • Certainty is measurable. Chance of rain is 30%. As for certainty as a mindset, please consider 'existential' instead of mindset - a specific vantage. Please see my answer for examples. Mar 10 '19 at 21:53
  • @Randy Zeitman, you equate chance with certainty. People can have different certainties about the "30%" chance of rain.
    – user96931
    Mar 14 '19 at 16:21

We most often use the term truth for indicating facts and often these facts seem to exist for a long period. But these also disappear after a certain period. We always experience something immutable even though there happens growth and development to our body. The only thing that can be certain is the true nature of oneself and it is the Ultimate Truth. One becomes completely satisfied with that only thing. Other things cannot satisfy him always. And the satisfaction is only because it is immutable and he is 100% certain about it. Actually I should use more than 100%. Since there is no usage like 1000%, 10000% (with certainty), I don't wish to use it.

The term 'Ananda' certainly conveys the certainty of something. https://en.wikipedia.org/wiki/%C4%80nanda_(Hindu_philosophy)

So I don't agree with this statement--"we cannot be certain about anything". IMHO, this is a wrong notion.

Also some people divided the things that we can know and the things we cannot, but even that have been doubted, so how exactly do we interpret this?

Read the description of the verse 7.7 of the Bhagavad Gita: https://www.bhagavad-gita.us/bhagavad-gita-7-7/

If this is true, our individual perception need not necessarily be 100% certain. There is a great chance of misapprehension. http://www.mahavidya.ca/2015/06/25/maya-the-concept-of-illusion/

So your doubt is reasonable, but except in the case of one thing and it is the thing that I have mentioned already. All other things come under the second category.

Does it mean that this rule simply isn't all around true and that we can know somethings with absolute certainty?

If you agree with the idea mentioned in the first para, the answer to this question must be "Yes".


It's completely absurd to say we cannot be 100% certain.

In fact we are 100% certain, existentially certain, of everything.

A simple example: You see someone across the street. Is that Joe? You're not sure.

So are you uncertain? Yep. 100%. Are you certain you're uncertain? Yep. 100%.

Conventionally you're not certain and there's no way to prove anything is 100% certain because how would that be determined? How can something be 'more than certain' to measure something is certain?

Existentially you're always 100% certain (that you are uncertain).

"It might rain tomorrow."

Are you sure? Absolutely.

Well that's 100% as "might" accounts for all possibilities.

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