If I understand it correctly, the problem of criterion is essentially that you can only identify knowledge if you have the criteria for knowledge, but that you can only have the criteria for knowledge if you can identify knowledge.

It seems to me that this would apply to all definitions, that is, supposing definitions worked that way to begin with. Doesn't definitions mean what we want them to mean? In the end, isn't "knowledge" just another word, a semantic tool, that has no inherit meaning other than the one we ascribe it?

I don't see what exactly is so problematic about the problem of criterion. However, I'm a beginner when it comes to epistemology, so I'm guessing I'm somehow getting this all wrong. Help is much appreciated.

4 Answers 4


You can get away with claiming knowledge is just a semantic tool with no inherent meaning other than the one we ascribe to it. However, many philosophies are written on an assumption that it is more than that. In particular, knowledge gets conveyed, and if you want to believe a particular piece of knowledge is "universal," it can be difficult to explain why you can simply assume the unspecified listener understands the knowledge correctly. You can imagine how hard it would be for Socrates to put knowledge on such a high pillar as he did if he also believed it was merely a semantic tool.

Many attempts to define knowledge as more than a semantic tool run into challenges describing knowledge about knowledge itself. This suggests that, in such theories, there are unknowable things. For some, this is unsatisfying. For instance, the inability to prove a true expression in mathematics is indeed true has frustrated many mathematicians. Nowhere has this been more evident than with Godel's incompleteness theorems, which demonstrated a large class of provably unprovable systems.


There's a problem with a purely arbitrary approach to the meaning of every word.

The most basic problem is that you understand what I mean. But a more advanced problem is that you know what I mean because you ascribe to each word non-arbitrary meaning and group these together as an intention.

In other words, on a certain "Wittgensteinian" level, there are rules to this language game. That's not a complete disproof of your point, but it is a necessary propaedeutic. Or to put it another way, it's arbitrary that the word knowledge is the world knowledge (or any way of saying it any language, e.g. Wissen, chishiki, le savoir ), but the basic concept (assuming a language has such a concept) is non-arbitrary.

And in this particular instance, the idea of the concept is that it's the concept of rightfully identifying the way the world is.

Thus, the word/concept unlike some other words contains an implication. The implication is that if you have knowledge, then you have knowledge of knowledge. But that if you lack knowledge, then you lack knowledge of knowledge.

For most other words and concepts, I could know it or not know it. I either know what a chocolate cake is or I don't. And I can check this by seeing whether I know it. But for the nature of knowledge, the thing to be checked and the thing that checks it are the same. Thus, the criterion problem.

We can now in a sense return to an objection you raise: what if "knowledge" is not what we think it is, i.e., what if this word is just like all the other words and concepts. In that case, I think your 100% correct, and that there's no special problem. But then the question is whether we've solved the criterion problem or just moved the goal posts.

And I think a major problem is going to be that it seems like to make sense of language and the way we think, you're going to have to accept there are at least a few words and concepts that aren't just arbitrary in what they do in the system. And one of them is going to be "did I get this right?" where this is the relation between the words I use and the world. That relation is going to suffer from the criterion problem since its condition is identical to its fulfillment.

Or so I would believe.

The school of thought that rejects that there's an underpinning to which our language attaches is called "post-structuralism." (though to be honest it's not that different from structuralism). You could look at Derrida, Kristeva, Barthes, or others if you're interested in denying the criterion problem and working with a wholly semantic concept of language.


Already Plato discussed the following definition of knowledge: To know means

  • to state a true proposition,
  • to believe that the proposition is true,
  • and to be able to argue why the proposition is true.

The discussion took place in Plato's dialogue Phaedo. Even when eventually the definition was not accepted, the reason was not the problem of criterion.

Nevertheless, the three characteristics above are often taken as definition of knowledge, also today. For today's objection see the Gettier problem, http://plato.stanford.edu/entries/knowledge-analysis/ . It shows that in some extreme cases the definition does not meet our intention.

You are right, in mathematics we are totally free how to define a concept, i.e. to give an arbitrary name to a concept. Here a definition is like baptizing: You are free to choose the name.

Like you, I cannot follow the argumentation expressed in the problem of criterion. To define a general type and to determine whether a special case is an instance of the type: Why is there a logical problem?


I think the core of the problem is this. Consider some piece of knowledge Y that enables you to tell whether any purported piece of knowledge X is actually knowledge. The problem would then be: can you use Y to identify whether Y is knowledge?

The way out of this problem is to realise that it is misconceived for at least two distinct reasons.

First, a criterion is basically a definition. A definition is a way of summarising an uncontroversial piece of knowledge so you can easily refer to it. A definition can't fulfil the role often assigned to it of allowing us to settle substantive using a dictionary because every definition uses undefined terms. So a definition always has some wiggle room for drawing different conclusions from it. So trying to settle whether some alleged item of knowledge is knowledge by appealing to a criterion is bound to fail. There is another reason why trying to settle issues by definitions is an extremely bad habit. A definition is only useful in the light of an explanation. Any remotely interesting explanation will have lots of unanticipated consequences that will require the definition of new terms to make discussion easier. But those definitions will only make sense if you understand the underlying explanation. Trying to discuss a definition in isolation is a recipe for confusion.

Second, the whole idea of the criterion presupposes that at some point you're going to have a closed set of rules for when something is knowledge. But if that is true, any unsolved problems written into the criterion can never be solved even in principle. Anything not included in the criterion is not knowledge and so the solution to any problem in the criterion is not knowledge.

Knowledge consists of solutions to problems. You create knowledge by noticing a problem, proposing solutions to it and then criticising the solutions until only one is left. There is no reason to think there is any criterion, and no call for one. For a better understanding of epistemology see "Realism and the Aim of Science" by Popper, Chapter I.

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