Let us suppose that I'm phoning someone abducted or kidnapped and the criminal who kidnapped him is aiming the gun at his head and ordering him to lead me to the trap he has set for me (in this case my ears have failed me and I was deceived and trapped)

Let's also suppose that I'm thinking that the size of the moon is as small as 50 cent coin because my eyes see it so (in this case my eyes have aslo failed me and I was deceived by the apparent size my eyes see)

In such cases when my senses [i.e., eyes, ears] fail me then how could I reach the truth?!

  • Get someone who has her 5 senses to tell you. This is the use of signs. Like language, sign language, Braille. You can also feel around for the truth, but make sure you have your medical papers with you to prove your need to feel around.
    – Gordon
    Commented Sep 7, 2017 at 1:09
  • Also, signs allow me to experience things I may never actually see or hear, feel etc. I have never been to Alaska, but I can "experience" it through signs (like language). So signs help me to extend my world beyond my immediate horizons (beyond my immediate ability to sense).
    – Gordon
    Commented Sep 7, 2017 at 2:20
  • If all your senses fail you, you'll be be far more concerned with mundane matters like how do you feed yourself, get a glass of water, cross the road when theres traffice about etc etc rather than troubling yourself with the 'truth'. Commented Sep 7, 2017 at 14:02
  • en.wikipedia.org/wiki/Brain_in_a_vat might be useful reading here.
    – user935
    Commented Sep 9, 2017 at 2:14
  • Perhaps it is a bit pedantic, but it seems to me in these situations that "your senses" are doing just fine; it is the interpretation of them that is lacking. For example, the moon can be eclipsed by a penny at the appropriate distance; but life experience should tell you (1) farther away things appear smaller than they are, and a little less obvious (2) "parallax" can be used to determine distance.
    – Uueerdo
    Commented Feb 3, 2020 at 17:53

4 Answers 4


Rationalism is the philosophical school of thought that the only way to reach the truth is through reason alone, since our senses (as you describe in your examples) are always fallible. Rationalism is usually contrasted with Empiricism, the position that our senses, despite being very error prone, are still the only reliable source we have.

DesCartes cogito is a famous example of rationalist thinking: He imagines that an evil demon is trying to deceive us and everything is really just an illusion, even our very existence is an illusion. He then tries to prove through reason and logic alone that this is impossible, and that even though we may doubt everything else, we can at least be certain of our own existence.

Similarly, Kant, who is halfway between being a rationalist and empiricist, tried to prove that some (but not all) truths about the world can be determined through reason alone. These types of truths he calls synthetic a priori.

See the Rationalism vs. Empiricism debate for more details.


The scientific mind is very tentative, subject to revision based on new evidence because we are never so sure about our senses.

If we know our senses are failing us, the right thing for us to do is to suspend judgement.

Take Arab spring for example. What evidence do you have that revolution will improve people's lives? The Cromwellian revolution killed a lot of people and created a dictator; American revolution created the world's largest mob rule, where envy ran riot and where nobody knew his place, and severed the connection between the new world and the locomotive of the world's civilization; the French revolution exterminated the best elements of the French people; Russian and China' communist revolution inflicted severe brain damage upon themselves. Even the sudden collapse of the Evil CCCP did not make things better; it made the Russians poorer and gave the rest of the world more nukes.

If you do not see any beneficent effects of revolution, a reasonable question that follows is this: how likely a revolution will make things worse?

The Brits averted a French style revolution in the first half 1800's - thanks to Macaulay's eloquence - things did change gradually for the better.

That all human knowledge is uncertain, inexact, and partial. To this doctrine we have not found any limitation whatever.

Russell, Bertrand. Human Knowledge Its Scope and limits. New York: Simon and Schuster, 1948. 507. Print.


No. But so what? You can use reason to determine the state of the world to whatever accuracy you find necessary to live your life.

I've never seen my face, but I'll bet you my entire net worth that I have one. Other beings that resemble me in the parts I can see all have faces and they tell me I have one. I can see reflections in some surfaces that resemble a face, and when I do things like touch where I presume my face to be, the image in the reflection does also (albeit reversed, and possibly distorted). For me at least, that's more than sufficient evidence for me to act according to the presumption that I have a face.

What level of evidence is sufficient for you to act on other propositions is up to you. But if you insist on things like certainty or perfect perception, then you'll have no useful life at all.


@Alexander S King's answer(+1) presents the standard positions regarding truth, but I think the concrete answer to your question is you can't. The rationalist perspective has been deprecated in most mature forms of philosophy in favor of empiricism and although Kant finds the coherence between both approaches, it sustains the empiricist position regarding the necessity of the senses to develop all forms of knowledge (including the aforementioned synthetic a priori, which is not the direct result of experience, but is indirectly dependent on it).

Therefore, given that the only interface we have with the world are our senses, then the truth is strictly not accessible and can't be known. Ergo, since we humans have all similar senses, it is quite possible that multiple beliefs that we consider truths are false.

For an example of our distrust in rational truth in favor of experience, see [1].

[1] https://theflatearthsociety.org/tiki/tiki-index.php?page=The+Moon

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .