What are some viewpoints on the following assertion in philosophy and logic?

Anything people argue to be true is only their assertion based on some axioms or premises which they assume to be true (cannot prove them).

Therefore it seems reasonable to me to claim that the only "truth" people are capable of knowing is the "truth" that they assume to be true in their reasoning. Also all the deduced "truths" from such true assumptions would be counted as such truths.

Could you please give me some insight to this idea? I do not have a philosophy nor logic background. Thank you!

  • This is called relativism. In your all-encompassing and naive form it is incoherent. Just apply what the statement says to it.
    – Conifold
    Aug 25, 2019 at 8:01
  • Truth can be used in different contexts. The main contexts are objective truths, & contingent truths. Contingent truths are those truths that are relative, personal, subjecrive. In other words these values can change in time or circumstances. Objective truth has a value that cannot change. You can't just say truth is truth & they are all the same. Can people assume relative truths? Yes. I doubt you can assume objective truths because you would just be wrong to claim x is true and it turns out false. There is no assumption. It is just you made a false statement. Assumptions aren't necessary.
    – Logikal
    Aug 26, 2019 at 17:11
  • I think what you are describing are actually beliefs. I think the best way to phrase it is that it doesn't matter how true something actually is, people will only factor it into their interpretations of the past and plans for the future if they believe it. Then the interesting question is why we believe certain things and not others. This is epistemology. Oct 26, 2020 at 15:29

6 Answers 6


For some, knowledge is "justified, true belief". Here is how Wikipedia describes it:

Justified true belief is a definition of knowledge that gained approval during the Enlightenment, 'justified' standing in contrast to 'revealed'. There have been attempts to trace it back to Plato and his dialogues.

By this definition we would not know something unless we also believed it to be true. For example, consider the sentence, "It is raining". We would not know it is raining until we believed it is raining and had some justification for that belief such as looking out the window.

This links knowledge of what is true with an attitude of belief toward what is known. That attitude of belief can be viewed as an assumption.

Wikipedia contributors. (2019, August 8). Belief. In Wikipedia, The Free Encyclopedia. Retrieved 13:06, August 24, 2019, from https://en.wikipedia.org/w/index.php?title=Belief&oldid=909987074


In epistemology, the traditional definition of knowledge is :

True, Justified, Belief


As per your reasoning, you said :

Therefore it seems reasonable to me to claim that the only "truth" people are capable of knowing is the "truth" that they assume to be true in their reasoning. Also all the deduced "truths" from such true assumptions would be counted as such truths.

According to the definition of knowledge, people sure are capable of knowing X as long as X is a bold truth (not only "truth" with double quotes), and there is a justification for X .. And they believe that X is true.

These conditions, of which truth and justification are out of one's control (you cannot control what is true, and you cannot provide a good justification or evidence if it is not available .. all you can do is believe it).

But hold on .. I find a problem with the word "assume"

An assumption cannot be "known", because you only assume what is unknown, what has no justification or truth.

So, according to your question, there is a problem with this part :

Therefore it seems reasonable to me to claim that the only "truth" people are capable of knowing is the "truth" that they assume to be true in their reasoning. Also all the deduced "truths" from such true assumptions would be counted as such truths.

Assumption and Knowledge cannot possibly coexist. Either you know X or you assume X and not both.

Let's consider an example :

  • Premise 1 : If Unicorns exist then they are beautiful
  • Premise 2 : Unicorns exist
  • Conclusion : Unicorns are beautiful.

Premise 1 is true because I know what a Unicorn is supposed to look like and I see it as a beautiful creature if it existed (my conditional is true, because I know the definition of a Unicorn, and it is true that if Unicorns existed, they they would be beautiful , this is justified because I saw paintings and cartoon of Unicorns).

Premise 2, this cannot be knowledge (it is not only a conditional, but an assertion) :

  • If Unicorns do not exist, then I cannot absolutely know Premise 2 .. I cannot know what is false.
  • I have no good evidence for the existence of Unicorns, Premise 2 is not justified, therefore : I cannot know it.
  • I do not believe that Unicorns exist, so I cannot know this assumption.

I can assume it, and because I can assume they exist (to build on that premise) , it is impossible to know it at the same time.

Hope this helps.

  • 1
    Yes, I understand your point but we cannot prove that what is justified is the truth. We cannot prove anything in the real world and therefore we can only believe that a statement we are proposing is true. We could be living in a virtual reality and the truth therefore would looked very different from what we see. In other words, we cannot know the absolute truth and therefore everything we label as the truth is just our assumption based on belief that our sensory data correlate with the reality (it could be some brain in the vat reality for example).
    – TKN
    Aug 25, 2019 at 7:00
  • @TKN You presuppose that there is something like absolute truth or provable truth. It can be and has been shown that there is no consistent meaningful way of speaking about an absolute truth. Truth is context sensitive and it has to be that way if it is to be expressed by language. So the question "But what if we are brains-in-vats" not only can be answered by "Would it make any meaningful difference for us?", it also is literal nonsense to even ask that question if there is no way to validate an answer.
    – Philip Klöcking
    Aug 25, 2019 at 16:32
  • Either you know x is true or you assume x is true and not both? Well the semantically many Mathematical people use hypothetical statements to prevent being proven wrong. Your use of the hypothetical in the unicorn example shows this. But all hypothetical statements have the same form but the content of what the propositions express are not identical. The form is identical though. So how do we tell the real truth from the hypothetical truths from he form If . . . THEN FORM?
    – Logikal
    Aug 26, 2019 at 17:24
  • 1
    On a deeper level, we assume pretty much everything we "claim" to know, and we base this only on justification and belief (but not truth, since there is no immediate access to the truth of things except through the senses and experience)... That's why I am a skeptic (I think that real knowledge is impossible), because most of our knowledge is based on assumptions.
    – SmootQ
    Aug 26, 2019 at 18:11
  • 1
    And if the truth is only partly detected through justification, then all of our knowledge is based on belief and justification, from which we assume that such and such justification must match or point to such and such truth. But we do not have any way to access truth (independent of justification). For example, we claim to know that there is a sun, (we believe it, good. Our belief is justified , also good. But is it true?) .. Well, this last part only comes from our "justification". There is no way to access this information without justification... We only assume it, we don't know it.
    – SmootQ
    Aug 26, 2019 at 18:15

There's a truism in philosophy that I like to trot out every once in a while: solipsism implies relativism. The only way we can validate the 'truth' or 'falsehood' of our understandings and beliefs is through our experience of the external world, and in particular our experience of other beings in the external world. I can only validate the statement "I see a red rose" by looking at someone else and saying: "Do you see a red rose too?". If they say 'yes' we have created a greater sense of validity than I could possibly achieve on my own; if they say 'no' then we have created a state of ambiguity is which neither of us can be sure we know the 'truth'.

The only way we can get a handle on 'objective' reality is to reach for intersubjective agreement about our mutual experiences. Trying to reduce knowledge to something 'owned' by an individual (at the expense of other individuals) creates paradoxes and confusions. I mean, sure... there's an intuition that we 'know' things: that I 'know' I see a red rose. But while the knowledge that I see it might be private, the knowledge that it exists must be public, or it isn't really knowledge at all. Consider that we would not know what 'red' or 'rose' were without a social context that gave those terms collective meaning. It is the rationalization and systematization of that collective meaning that we generally refer to as 'knowledge'.

If I look out the window and say "It's raining", and you look out the same window and say "It's sunny", who's right? Perhaps I think blue skies are rain; perhaps you think raindrops are sunbeams... We don't know who's right until we reach some kind of agreement, and once we've reach that agreement, we have knowledge.

  • To add to that, this reaches into the plane of language and its own validity as well, ie can be said about language tokens just as well as about propositional content (syntactic as well as semantic layer). Not only we do have the normative interpersonal agreement that we both see a red rose over there, we also have the normative interpersonal agreement that uttering the language token "I see a red rose over there" is the appropriate behaviour corresponding with the sensation of seeing a red rose (and that it's a sensation). And that this utterance indicates (or constitutes) knowledge.
    – Philip Klöcking
    Aug 25, 2019 at 16:21

Good reasoning!

This is true in the case of Conventional truth. The usage of the qualifying term 'conventional' itself shows its limitation. Also, as we know, it changes after some or certain periods. If we have more sense organs or powerful sense organs (or both) our perception would be different and so the assumption or the truth we know would also be different.

There is 'another'/higher truth called the Ultimate Truth. It is the immutable ultimate reality. Some people call it God or something like that. The realization of this also is possible for humans. When one realizes this, he realizes that it is the immutable ultimate reality. Here, there is no chance of possibilities as you mentioned because he also realizes that there is nothing second to destroy it. Actually, by truth realization we mean its realization. The person will be convinced this by himself without any doubt. Truth realization would be possible only by transcending one's sense organs. The number or power or sense organs can't do anything here. The wise call it ānanda also while trying to specify that truth. Even without the help of any of the sense organs, that truth is ānanda which means 'happiness, joy, enjoyment, bliss or pure happiness'. Only the Ultimate truth can give the eternal peace.

Three Levels of Reality.

We have understood that Brahman appears in different forms in association with upAdhis, though He is not subject to any limitation and can not be described at the speech and mind level. The truth at the supreme level (paramArTha) is the only Reality, while what is observable at the transactional or relational level is not the reality. However the common experience of people is to recognize the body / mind level experiences as reality. Keeping this in mind, the vEdAnta recognizes three levels of reality as follows;

pAramArThika satya or Supreme Reality

vyAvahArika satya or Trancactional Reality

prAtibhAsika satya or Apparent Reality.

These three levels of reality can be better understood through an example. An image of an object can be captured on a screen through a lens. The clarity of the image is dependent on the distance between the lens and the screen, the orientation of the screen, lighting conditions etc. This image is available to everyone's experiences. Under other circumstances, an apparent image of the object (virtual image) can be seen, by a select few in some specific orientation (This will not be the experience of all, as in the lens image above).

It is not possible to capture this image and cannot be a transactional experience, though can be seen (think of a creative artwork, which at an angle, will look something differently). In this example, the object is the pAramArThika satya, the lens image is the vyAvahArika satya and the apparent image is the prAtibhAsika satya. In the backdrop of this example, we can understand the three levels of reality in the philosophical plane.

Brahman is Real is the pAramArThika satya. This is the statement of shrutis. The experience of the sense organs keeps changing from time to time or person to person; what is changing can only be the experiences of the sense organs as Science has demonstrated to us. Even in ordinary experiences this is true - like the change in the musical speed can only be determined with respect to a metronome. Brahman is beyond sense organs and is unchanging and is the Supreme Reality.

The jagat is constantly changing and this change is experienced by the five sense organs. This change is the common experience of all (without defects in sense organs). The knowledge thus established through the sense organs is the basis of all transactional activities. The shAstra classifies this changing jagat experienced by all and being the basis of all transactions as vyAvahArika satya.

A traveler, on a hot afternoon, sees water at a distance. When he arrives at that location, the water that we all have come to know is not to be seen. The water is a mirage. It appears to be there, but it is not there. This experience, dependent on time and space, is called prAtibhAsika satya. This experience is also called "satya", though it is an apparent experience, because Brahman is the substratum supporting this apparent experience - the laws of nature support the mirage.

Though the three levels of reality are conceded by the shAstra, the pAramArThika satya is the supporting Reality for the Transactional Reality and the Apparent Reality. As much as the Apparent Reality is unreal with respect to the Transactional Reality, so is the Transactional Reality is unreal with respect to the Supreme Reality.

  1. All axioms are assumed, thus the point of the observer is constant as an underlying form. Socrates blanck slate or zen beginners mind (both observing the a priori state of mind as a boundless plane) necessitates a single point as a constant form. The dot is the most universal of axioms.

  2. The continual seperation and connection of axioms requires a linear continuum, thus the line is a continual form.

  3. The self referential nature of axioms, where 1 (as purely assumed) leading to 2, then 3 (as the self referencing of 1) necessitates circularity, thus the circle is a continual form.

  4. This observes the Munchauseen trillema (points 1 through 3) as having inherent platonic forms where any variation in assumption is a variation of how a simple point, line and circle (the circumpunct or monad observed in all cultures) occurs in an infinite variation.

  5. All relative truth is an approximation of one absolute truth through various truths. Truth is assumed, and the nature of assumption (as evidenced through the trillema) exists through forms. Reversely, relativistic truth (as many interrelated truths) exist as a progression towards one truth. This progression is "the one" self referencing itself as infinite movement in accords to "the 24 philosophers".

  6. Thus truth is ever renewing form through a process of hegelian synthesis.

So truth is:

Absolute Relative Synthetic

As a triad of these qualities. Proof is merely the definition of axioms resulting in a "form" which exists "as is". One proof is greater or less than another proof by its inherent connection of axioms, but this does not necessitate a false proof as having "no truth"...just disconnected assumptions.

  1. Assumption=Truth=Form where form exists "as is". So yes all is assumed, but assumption is a truth statement based upon the self evident forms it manifests.

Hopefully this makes sense. In simpler terms we only assumed forms (abstract and empirical) with the nature of assumption taking on a form in and of itself.

  • Why do we need to start with axioms from the beginning? Canyon I know stuff without assumptions? Can I know all women are human beings without an assumption? Seems to me that I can do so. I can make claims without assumption. Your answer only covers assumption as if there were no other possibilities. If that is what you meant then you did not make it explicitly clear in your answer.
    – Logikal
    Aug 26, 2019 at 17:15
  • All logics are grounded in rules which are assumed. A line between two points is one axiom of Euclid, however that axiom is now called a line segment and the line is now a boundless length. One axiom diverges into another while repeating some common assumption (ie the line). I use this as an example partially because when we assume one axiom we define it through another than another, thus not only is the axiom defined by an inherent form but the nature of assumption as well. We assume through forms with assumptions taking a point, linear and circular form. Assumption, truth, form are one.
    – Eodnhoj7
    Aug 26, 2019 at 17:31
  • Assumption is universal, but it does not negate constant truth as we assume constant truth, just as we assume falsity. Proof for either is strictly just definition as the connection of further assumptions.
    – Eodnhoj7
    Aug 26, 2019 at 17:34
  • Can you show me axioms that are used in Aristotelian logic. Surely o dont need the three famous laws as axioms to derive conclusions of categorical syllogisms. I think you mean assumptions are required for Mathematical logic specifically. I am sure I can and you can resolve a syllogism without making any assumptions whatsoever.
    – Logikal
    Aug 26, 2019 at 17:37
  • Besides the law of identity, non contradiction and excluded middle? The variable as the generalization of many phenomenon which in itself is grounded in assumption. The variable of "P" is a localization of a continuum of axioms into one generality that is strictly assumed. When I assume something, take it as is, it is deductive by nature as a localized an atomic truth of a general truth. Dually I localize a set of atomics truths into a general truth which in turn is an atomic truth of some other generality. To assume effectively is to individuate some portion of reality, this is deductive.
    – Eodnhoj7
    Aug 26, 2019 at 19:27

Short answer: if it was the case we would never be surprised. If everything we can comprehend has to be part of our preconception, we would never acquire unexpected knowledge.

Think of the scientists who revolutionized their field by producing new, at the time inconceivable, results, like the Rutherford experiment, or who produced theoretical approaches that worked, yet so unorthodox they could not accept it themselves, like Planck proposing that energy is quantized.

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