What constitutes valid knowledge in philosophy? I am not asking what is valid knowledge from an analytic standpoint nor am I asking for a definition of valid knowledge. I am asking what is valid knowledge in philosophy.

In Eastern philosophy, many philosophers of different persuasions have developed answers around what is called The Theory of Error. As part of their various theories, they define what constitutes valid knowledge and invalid knowledge. For example, one says a firm or assured cognition which does not stand in need of confirmation by other cognitions constitutes valid knowledge. In other words, free from doubt and true. Another says it must also be novel; a knowledge which does not add something to our present stock of information cannot be valid. There are many more examples.

What constitutes valid knowledge in Western philosophy?

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    Are you asking what a particular philosopher defined "valid knowledge in philosophy" to mean? I'm rather certain there is not a strong consensus on the topic. – Cort Ammon Sep 18 '15 at 7:27
  • @CortAmmon No particular philosopher. Would be surprised if there was a consensus...interested in what different philosophers/philosophies have said to see if there is any commonality. – Swami Vishwananda Sep 18 '15 at 10:08
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    I think one could probably write a long paper on any one particular philosopher's ideas about this, so to ask about it in general will lead to unwieldy answers. – James Kingsbery Sep 18 '15 at 14:48
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    This does seem to be a very broad question. – davidlowryduda Sep 18 '15 at 16:01
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    So "Valid Knowledge" is two words in English. Google ngrams shows that its usage jumped 3fold in 1940 but tapered in 1980. Words often have many shades of meaning, especially in philosophy, especially when translation between languages has to occur and different translators take different liberties. It might help if you explain what meanings you are looking for when you ask the question. It's clear you have something very specific in your mind, but I don't think it's quite coming across with the wording of the question. – Cort Ammon Sep 18 '15 at 17:54

The first Western philosopher who discusses explicitly the concept of knowledge - in the sense of valid knowledge from your question - is Plato. His term for knowledge is episteme. Plato contrasts knowledge to mere meaning which is termed doxa.

Plato discusses the subject in his dialogue Theaitetos (145e ff.). After several unsuccessfull attempts the dialogue partner proposes the definition (201d):

Knowledge (episteme) is true (alaethaes) meaning (doxa) supported by an argument (logos).

This definition shows what is necessary to constitute knowledge:

  • Knowledge has to be expressed in propositions,
  • knowledge must be true and
  • one must be able to argue for the truth of knowledge.

Interestingly, in the end of the dialogue Plato rejects also this definition (208b11).

After more than 2000 years of Western philosophy it was Karl Popper who gave the whole discussion, whether valid knowledge is possible, quite a new turn. Popper abandoned all unavailing attempts to find valid knowledge about general topics different from mathematical truths. Popper's principle of falsification states that such general knowledge is always hypothetical and cannot be verified but only falsified. But falsification prompts for new and better hypotheses.


These are I think fairly general features which apply generally to a philosophy, to the extent it can - meaning in competition or dialogue with another philosophy. Say, in choosing Descartes Philosophy - though Spinoza could do equally as well:

For example, one says a firm or assured cognition which does not stand in need of confirmation by other cognitions constitutes valid knowledge.

This is the context in which Descarte begins with his cogito; but this is through his encounter with Avicennas Floating Man.

In other words, free from doubt and true.

In itself the cogito is free of doubt and true; but just by itself it leads to solipsism, or men considered as mental atoms; hence the modern theory of the Subject in European philosophy is more about inter-subjectivity.

Another says it must also be novel

The cogito when understood to be in descent from Avicenna is not novel; for Avicenna too, was arguing for what constitutes certain knowledge; but is novel in how it is later theorised (see above).

a knowledge which does not add something to our present stock of information cannot be valid.

Physicists have been arguing that philosophers have done nothing for physics (a charge they don't level to other disciplines of the intellect - ie historians) due to their historical relationship; but one needs to recall those philosophers were called philosophers of Nature - and in a different aspect that tradition has continued - ie Naess's deep ecology; of which Naess admits an influence from Gandhi

There are many more examples.

One fascinating link for me is how language itself informed early Indian philosophy; for example Paninis grammar as a form of the axiomatic, which in the Western tradition is traditionally indexed by Euclid.

It is true though that Indian philosophy in the west is hardly engaged on its own terms; with even the influence that it has had as an underground influence, say on Emerson or Schopenhauer barely acknowledged; but is this also the case for Indian philosophy in India? Garfield and Bhushan for example in this essay explores the situation for such philosophy written in English taking a single exemplar, Mukherjee of Allahabad and concluding:

This period saw a vibrant engagement with philosophical ideas and questions emerging from the Indian Vedic tradition

But languished in obscurity since the institutional support wasn't there; with Mukherjees work, published in the Allahabad University Studies which was never distributed nationally and exist only in:

seriously moth and termite-infested almirahs scattered through India.

To which situation they have mounted a limited rescue operation, publishing a selection of essays from these thinkers in Indian Philosophy in English; to which the NDPR respond that the complaint by Daya Krishna that Indian Philosophy isn't taken seriously by Western philosophers, have been shown the evidence; and it's a matter now of its reception.


Say we have knowledge that consists of arbitrary propositions A, B, C

We might say If A ^ B then C A exists B exists Conclusion C exists.

This argument is logically valid. But what if B does not really exist? Then the argument is not logically sound. For this example let's say that A does in fact exist.

Valid knowledge would be A. Invalid knowledge would be B.

A is sometimes called Justified true belief

Because A is true We believe A and We are justified in believing A (Because it is true)

So far this is pretty uncontroversial, but epistemology is a large field. The study of knowledge, and how it is acquired raises many philosophical questions. Further, it is an area that could be considered "practical philosophy" in that knowing how to correctly acquire correct knowledge would be a skill set with practical uses in the world. As such it has a large impact to science and other fields.

So one who is skeptical of A might ask you "How do you know A is the case?" If you merely reply "Because A is true" they likely will not be satisfied. You must in some way show that A is true, not merely claim it.

Here are some theories of epistemology :

Pyrrhonism - a branch of skepticism that does not believe in the reality of "absolutely certain knowledge" They refrain from making truth claims all together

Coherentism Note their view on skeptisim of an external world

(Brain in a vat / trapped in virtual reality / universe is a simulation arguements)

As an illustration of the principle, if people lived in a virtual reality universe, they could see birds in the trees that aren't really there. Not only are the birds not really there, but the trees aren't really there either. The people know that the bird and the tree are there, because it coheres with the rest of their experiences in the virtual reality. Talking about coherence is an abstract way of talking about the things that the people really know, without regard for whether they are in a virtual reality or not.

Functional Contextualism



Internalism and externalism



Metaphysical Anti-Realism

And on and on (Feel free to edit and add theories I may have left out.)

All of these theories have their own stances on what makes knowledge valid, and how to justify proposition A.

  • From my point of view this is much better than your other answer, although it's currently rated lower. The biggest red flag might be that it uses the phrase "pretty uncontroversial." Nothing is "pretty uncontroversial" in philosophy. FWIW, however, I put an upvote on this one. The problems with this answer are really problems with the question, in my opinion. – Chris Sunami supports Monica Sep 21 '15 at 16:39
  • I agree, but in epistemology, besides the exceptions I've listed (Mostly skeptical theories ) most theories agree with that top paragraph. Perhaps I missed some theories, or the field has changed significantly since I studied it. – hellyale Sep 21 '15 at 16:47

Let's try a more concrete and simpler example then....

Here is an image of the moon through a sun roof of a car :

enter image description here

You were looking at a digital reconstruction of an image taken through my phones camera.

This image contains within it sunlight that was being reflected off the moon, ~8min before the time at which I took the picture.

Before it could be digitally reconstructed on your viewing device, it had to travel across the air, (possibly even to the tower in view) server wires, and your internet connection etc....

These statements would be considered valid knowledge by the majority of philosophers.

Barring of course the theories with exceptions in my previous answer.

  • If the down voter could say why... – hellyale Sep 20 '15 at 6:47
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    -1 (a) because you make a claim (the line starting with "these statements would be...") neither stating the reasoning behind it nor offering citations that support you, (b) because this answer apparently does not stand alone without your other answer and (c) because of the completely irrelevant speculation about other users of the site. The SE model is to provide a collection of reference quality answers, not to converse on the topic. – Chris Sunami supports Monica Sep 21 '15 at 16:34
  • @ChrisSunami thanks for the feedback. I addressed C and will consider how to best address A and B – hellyale Sep 21 '15 at 16:49

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