The attempt to define the concept of knowledge is not simple, and even though thinkers have been trying to do so for over 2400 years, the curtain has not yet fallen on the last act
Marius Cohen, Galileo
Our lives revolve around knowing these and other facts: we know where we live, who our friends are, where we are headed, what time the news is broadcast, who is the president of the country, and so on. The ability to know is essential to our lives and without it we would be like leaves blowing in the wind, moving aimlessly and without orientation in the world. But what is knowledge itself? How do we know? What things can be known? What types of information are there? Is there a certain knowledge? And what is the relationship between the way we perceive reality and reality itself? These and other questions, concerning the concept of knowledge and the perception of reality, are the concern of epistemology - the theory of knowledge (or: the theory of cognition).
Different types of knowledge
The concept of knowledge is used by us in different ways: we know that the earth revolves around the sun, that Einstein was a great physicist and that Tel Aviv is on the coast of the Mediterranean Sea;
But we also know the alphabet, we know algebra (did I get carried away?), we know the way home, and we know how to swim and ride a bike. Although the concept of knowledge is used in all these examples, it is possible to distinguish between two different types of knowledge that appear in them: when we say that we know the alphabet, the way home or to ride a bicycle, we mean that we have a certain ability. On the other hand, the knowledge that the earth revolves around the sun, that Einstein was a great physicist and that Tel Aviv is on the coast of the Mediterranean Sea is knowledge of facts. Knowledge of the first type is called "ability knowledge or knowledge-how". Information of the second type is known as propositional information (from the word "proposition": claim, statement), and we will deal with it in this column.
A false statement cannot be considered knowledge. A person who believes that Einstein was a famous actor is not said to know that Einstein was an actor. If so, a necessary condition for any agreement to be considered knowledge is that this agreement be true.
We see, then, that at least two conditions must be met for us to agree that so-and-so knows that p, inasmuch as p is some proposition. So-and-so must believe that p, and the claim p must be true. If one of these two conditions is not met, we cannot say of a so-and-so that he knows that p. We can say of him that he only believes that p (if p is a false claim), or that he does not know that p (if p is a true claim but he does not believe it).
But are these two conditions (which together are called true belief) the only necessary conditions for knowledge? To examine this issue, let's imagine the following scenario: a certain person, who buys lottery tickets on a regular basis, believes with all his heart (not just hopes, but is convinced of this), that his investment will pay off sooner or later, and that one day he will win the big prize. Indeed, one day this person is informed that the last lottery ticket he purchased won him the big prize, making him a rich man. The happy winner goes out of his way with joy and shouts: "I knew it! I have known!". But did he really know he would win? Undoubtedly, this is a real treaty: he believed he would win the big prize and he did win it. However, it seems that we cannot say that that person did know that he would win. He believed he would win and he did, but there was no actual knowledge involved.
why? Because that person's belief in his future winnings was not justified. The probability of such an unusual event is so low that he had no valid reason to believe that he would ever win the grand prize. If his belief had a solid foundation - if, for example, the person responsible for the results of the lottery was a good friend or family member who promised to "fix" the results of the lottery, so that his ticket would win the big prize - we would be entitled to claim that that person did know that he would win. There was a basis for his belief, as someone who could influence the results of the lottery promised to see to it that he won. But in our story the belief of the happy winner had no basis, and therefore even if he was convinced that he would win, he only believed it; He didn't really know that.
Getty case
The above example implies that true belief is not sufficient to establish knowledge. It is important that the treaty also have a solid foundation; It is important to be able to justify the way in which it was formed. This concept, that knowledge is a true and justified agreement, is already known from the writings of Plato, a Greek philosopher of the fifth and fourth centuries BC. In the dialogue called "Theaetetus" Socrates, Plato's teacher, leads a young man named Theaetetus, later a talented geometrician, to a conclusion about the essence of knowledge:
"A correct opinion that is accompanied by a logical explanation is knowledge, but a correct opinion that is not accompanied by a logical explanation is outside the fence of knowledge"
However, later in the dialogue, Socrates also disapproves of this position, and apparently, the effort to find a catchy definition for the concept of knowledge has not ended until our very day, when there are many difficulties standing in the way of achieving this goal.
The story of a young American professor of philosophy named Edmund Gettier, who in the early 60's of the last century was looking for an easy topic to write an article that would buy him tenure in his job. Although he did not show much interest in epistemology (the theory of knowledge), it seemed to him that he was able to offer examples in which even a true and justified convention does not deserve to be considered knowledge, and he wrote a short article about it that gained worldwide resonance and which gave him the certainty he desired. To this day the examples he gave and examples similar to them are called Getty cases.
Here is an example: Let's imagine a person looking out the window of his friend's house and saying to his friend who is sitting in the room: "Your wife has arrived." His friend got up, went to open the door for his wife, and she entered and wondered how her husband knew about her arrival. Did this man know that his wife had arrived home before he saw her standing at the door? Well, he must have believed it, and as proof he got up to open the door for her. Since his wife did appear at the door, it was the real deal. And what about the justification of the treaty? Did he have good reason to believe that his wife had indeed arrived? for sure. He did not guess it or dream it; He relied on information he received from his good friend, who was in a position that allowed him to see anyone who approached the front of the house.
But what if it turned out that, in this case, his friend did not see his wife at all, but was greedy for money (it is possible that the two planned to watch a football game on TV and "down" a few beers, and hoped to do so without interruption). Completely by chance, and such coincidences do happen sometimes, the woman arrived from the direction of the backyard of the house at a time that matched the friend's joke. Since her husband opened the door for her, the woman was convinced that he did know about her arrival, and the husband also thought so until his friend, who himself was surprised by the extraordinary coincidence, confessed his teasing.
In light of this sequence of events, do we want to say that the husband really knew that his wife had arrived? On the one hand, he believed this, and his belief was true and justified (suppose his friend had never betrayed him before); But luck played a decisive role here: it was only the hand of chance that the arrival of his wife coincided with his friend's joke, and without this coincidence the husband's belief that his wife had arrived would have turned out to be false. Therefore, the "information" that the friend provided had no value in itself, and it cannot be considered as a basis for knowledge.
This example shows that it is possible to have a justified false belief, that is, to have a certain belief that does not correspond to reality, and that there would be good reasons to hold it (this is exactly what would have happened if the friend's wife had not come home at the right time). All Getty cases are based on a situation in which it is justified to hold the treaty, which would normally turn out to be false, but by an extraordinary coincidence the treaty turns out to be true. In each of these cases we cannot say that the person knows what he believes in: although there is justification for his belief, this belief is true only by chance, and therefore there is no cognitive achievement here; Even though it is a true and justified treaty - this is not news. Conclusion: Contrary to the tradition that preceded Gettier, we understand today that knowledge is not summed up in a true and justified convention, and that something is still missing.
Attempts to get out of the tangle
Gettier's examples shook those involved in the theory of knowledge, and even though there were those who thought it would be possible to avoid Gettier's cases through a more sophisticated definition of the concept of justification, it turned out that it is not that simple. One of the proposals was, for example, to demand that a true treaty not be based on false background assumptions.
In the above case, the person formed his belief about his wife's arrival home based on the assumption that his friend was telling the truth (it is possible that this assumption did not form an actual thought for him, but his behavior indicates that it was present in the background). But this assumption was false (his friend was not telling the truth), and therefore such a demand would prevent his belief about his wife's arrival from being news even though it was true and justified. However, this kind of demand is too strong and if we adopt it then many of the arts, which we want to see as news, will be considered true and justified arts that are not news. It will be very difficult to find the convention (false or real) that does not rely on even a false background assumption, and thus we will have to give up almost all of our knowledge, and see it as the convention only, even if it is true and justified (it is important to mention again that "false" does not necessarily mean an intentional and conscious lie , but not real).
Another way to try and define the concept of knowledge so that it is immune to Getiye cases is to demand that the fact that we believe in its correctness will be the reason (directly or indirectly) for the formation of our agreement. For example, if I believe that man evolved from an ancient mammal in an evolutionary way, and if this is indeed the case (as modern science holds), then I have a true belief, and it is also justified because it is based on the writings of scientists from different schools of thought (biologists, geologists, anthropologists, paleontologists and others), who base their writings on many findings that confirm the theory.
And how does the requirement that the fact itself be the reason for the formation of our treaty come into play? Well, the evolution of man from an ancient mammal left its traces on the environment (for example, skeletons from different prehistoric periods), these traces led scientists to propose the theory, to substantiate it and to write about it, and it was their writings that ultimately led to the formation of the doctrine. Since the fact that I believe in its correctness (evolutionary development of man from an ancient mammal) started a causal chain that ended in the formation of my belief, then according to this epistemological conception I do know that man evolved from an ancient mammal. And how does this requirement inoculate the concept of knowledge from Getty cases?
In the example we described, the boyfriend didn't see the wife coming, and therefore, even though the husband formed a genuine agreement regarding the matter, which was also justified (since it was based on the testimony of a good friend who had never accused him before), it was not the arrival of the wife at home that started the causal chain which resulted in the formation of the husband's agreement (he would have established this agreement even if she had not arrived home at this perfect time), and for that reason his agreement is not considered news.
Apparently, the requirement for a causal connection between the fact and the belief in its correctness solves the problem, and it also makes a lot of sense, since if the formation of the belief was caused (directly or indirectly) by the fact itself, it seems that the element of luck is out of the picture. But the epistemologists very quickly realized that the picture is not so rosy after all: suppose, for example, that when the woman came through the backyard she caused a street cat to run in panic to the front of the house, and the friend, who looked out the window and saw the cat, remembered the hanging that his friend hung him in (which involved a cat) A few weeks earlier and decided to pay him back as his reward. In this scenario, the wife's coming home did start a causal chain that eventually led to the formation of the husband's true and justified belief about her arrival...
If so, what is knowledge?
The attempts to find a better definition for the concept of knowledge continue to this day, and it seems that for every possible definition a counterexample can also be found. There are philosophers, and in particular epistemologists (who are called "skeptics" because of their position), who throw up their hands and state that in fact nothing can be known, and there are those who compromise on definitions that are not perfect, but suitable for most cases that we would like to consider as knowledge.
One such definition holds that the true covenant must be formed reliably in relation to the circumstances that led to its formation. In our example, the circumstances that led to the formation of the husband's confession included the boyfriend's intention to impose on him, and in these circumstances his testimony is not reliable, and therefore the husband's confession is not considered knowledge. On the other hand, if the boyfriend had actually seen the woman arriving, and if his report had been true, then under these circumstances his testimony would have been reliable and the husband's belief regarding his wife's arrival would have been considered news. The advantage of such a definition is that it does not place all responsibility for the formation of a true covenant on the person himself (through the demand for justification), and leaves an essential role also for external conditions that are beyond his control. Also, contrary to the requirement for the existence of a causal chain between the fact and the belief, which, as we have seen, still allows the element of luck to be a link in the chain, here the definition makes it difficult for luck to play a role, since if luck enters the picture, then it must be assumed that in the circumstances created, credibility will be damaged in the way the belief was formed. But even this conception of the concept of knowledge is not completely immune to counterexamples (can you think of one?) and efforts to better define the concept of knowledge are still ongoing.
Dr. Marius Cohen teaches philosophy at Ben-Gurion University. The full article was published in the magazine "Galileo and Innovations"
40 תגובות
Well.. end of argument.
Regarding the example of cycling.
It is certainly not true or at least not accurate according to my explanation to say "I know how to ride a bicycle".
Riding a bike is an action, not an emotion. The knowledge, for its part, can know about the occurrence of this or that emotion and nothing else.
This statement should be translated into the more accurate statement: "I know that I feel that I can ride a bicycle."
point:
Definately not.
On the contrary.
In my words there are two types of claims.
One type is the factual claims and the other type is claims regarding the preferred way of using these or other words.
The factual claims - if they are true (and I am convinced that they are) cannot lead to contradictions.
The claims about the preferred way to use words is intended to avoid contradictions by choosing different words to represent different things.
For example - knowing how to ride a bicycle is not the same as knowing how to solve a quadratic equation.
The first knowledge is not conscious knowledge in the full sense of the word because it is not based on declarative knowledge. This is why teaching a robot to do this required serious research and development.
The second knowledge is knowledge of declarative knowledge and therefore it is easy to teach a computer to solve a quadratic equation.
As a principle - when you say that the real question is what it is to know, you are making a mistake in the category because to know what "to know" is, in terms of the spoken language, you just have to ask a lot of people and choose the most common meaning.
The question I tried to discuss (and in fact the whole discussion revolves around it) is the question of how we *should* define knowledge.
abandoned.
Not important.
The real question is, what is knowing, for example how is it possible that the knowledge knows about the evidence. (How is it that I know I see and hear, etc.). And what is the meaning of the program of this news.
I think I understand what you are trying to say.
But claims like you make about the soul lead to contradictions and paradoxes in the understanding of the soul.
point:
I don't think you understood my point, but I'm afraid we've argued enough.
Knowing itself is a type of emotion like the other emotions, for example the emotion of seeing and hearing (I usually call all conscious mental processes as emotion).
Knowing something and being aware of something is what we are. Therefore, anything that a person is aware of (for example, that he sees, or for example that he knows) he knows it.
And hence man always knows that he knows. It is not possible otherwise. That is, it is not possible that he did not know what he knows. And things are clear.
Dot and Higgs:
It seems to me that you are missing an important point here (and Higgs is just as important 🙂 ).
Do you know that you know is an indefinite question because the word "knows" must be accompanied by the object of knowledge.
You can know something.
You can't just know.
In the phrase "you know that you know" there is a beginning of the description of the object of the knowledge of the first verb but there is no description of the object of the knowledge in the second verb and therefore the description of the object of the knowledge of the first verb is also incomplete.
The question "Do you know that you know how to solve a quadratic equation?" It is a defined, legitimate and answerable question. The answer is indeed trivial because it is difficult to know how to solve a quadratic equation without knowing that you know, but if you recall the article on blind sight you see that this type of question is not always trivial and that if we ask someone with blind sight if he knows how to walk in a room without encountering obstacles, he will answer in the negative even though he will succeed in completing the task.
Here we are already getting into subtleties of a different kind in the definition of the concept of "knowledge" and the question of whether knowledge must be conscious is a legitimate question that should be decided what the answer to it is.
In my opinion, unconscious knowledge - it is better not to call it knowledge because it is a different state of mind. I would say that a person who only sees blindsight can walk in a room without encountering obstacles but does not know how to do so.
If you really want to be precise, I would also say that a person can usually ride a bicycle but does not know how to do it, even though he does know that he can ride a bicycle.
The looping questions that Higgs aimed at are questions of a different kind - those based on self-reference - but the question he brought as an example is actually not a question of this kind.
higgs,
The question of whether you know that you know is not an infinite loop. It generally clarifies what kind of things we know or can know.
The question eventually translates into the question: Is the knowledge I know the same as the knowledge I see.
And the answer is, as everyone knows, positive.
The catch phrase "do you know that you know" like all these other paradoxes, "is the liar lying or telling the truth when he claims to have lied".
Logical loops by their nature are suitable for philosophical discussions with no real decision for those who are interested and have extra time.
Science is indeed based on logic, but serious scientists do not seek to engage in endless looping problems. There are many situations in quantum physics, such as the uncertainty principle and the duality of particles, when the binding between different components is very tight and loopy in certain ways. However, accurate and plausible solutions have been found using probabilistic averaging methods and more to practically solve problems of this type.
Anyone who has studied a bit of programming knows that infinite loops are bugs that should be removed from the program.
This is exactly their idea, to waste my precious time when I can write new articles. I will take care of it in the evening.
Father, can you delete the disturbing unrelated messages.
splendor:
In my opinion, none of the perceptions of truth that you described is the accepted and justified perception of truth.
The truth is - literally - the collection of all the correct claims. It doesn't matter at all how you get to them (whether through the experience of the senses or through logical reasoning) and it doesn't even matter if you get to them at all (truth is truth even if no one knows it. That's why evolution was true even before there were humans).
I didn't read Yuval Steinitz's first book, but I read his book "A Logical Scientific Missile to God and Back" many years ago and I had a nausea that has not passed to this day. I don't think I'll ever read another book by him.
Lior:
Explain, detail and reason (or apologize for wasting time).
In my opinion, the theory of knowledge is a section of quantum physics
I don't find any special connection between the concept of "truth" and the concept of knowing.
There are (at least) two perceptions, one that says, the truth is what is perceived by the senses
And the second you say, the truth is what is logically correct
And there are all kinds of mixtures between them (when most of the time the concept of truth refers to the universe and existence)
In the first view, sight and hearing are proof of the truth (or part of it - only what is perceived by the senses exists.
And in the second only what we have proven exists.
First, there is a lot of information, because there is a lot of information that some of us absorb with the help of our senses, and then of course there is the problem of whether everyone sees the same things...and whether things we don't see don't exist, etc.
In the second, I think that means I exist, very little more than that...
And there are all the concepts that confuse the two (duality).
In the excellent book - An Invitation to Philosophy, by Yuval Shtinitz - explains in a simple and clear way the theory of recognition and more.. Recommended for those for whom this book is a sufficiently certain recognition 🙂
Indeed, all mistakes of this type stem from improper use of language.
The problem with mental processes is that they cannot be pointed out in the same way that a red object is pointed out.
True - but the discussion was created because not everyone understands the term.
Even more than that - not everyone defines it the way we define it.
In principle, this is their right - after all, as we know - language is a statistical phenomenon in which it is usually correct to say that "the majority decides".
The problem is that an "objective" definition of knowledge (just like an "objective" definition of morality - if you remember our discussion on this issue) creates communication problems and therefore - in this case - it is desirable to convince the "determining majority" to determine a meaning free from internal contradictions.
As far as I am concerned, the purpose of the discussion is - therefore - to point out the problematic of using the term "knowledge" to describe an objective situation. There is no possibility of pointing out this problematic by waving my definition of the term and we must refer to the alternative definitions and explain what is wrong with them.
Knowing is definitely a state of mind.
And just as it is not possible to argue about the red color we see, so it is not possible to argue about what we know. All in all, the term needs to be clarified. Like explaining to a child what the color red is by pointing to something red in color.
point:
That's why I said that knowing is a state of mind.
The fact that it is possible to reach an agreement on the essence of the news does not mean that the discussion of the question is worthless.
That is, the statement "I know it's true" should be translated into the more accurate statement "I know I feel it's true"
Michael, I know I think what I think. The question of the correctness of the matter is generally a question of belief/conclusion and not of knowledge.
There is nothing to get involved in.
fresh:
Not true.
First of all - since knowledge is a subjective feeling, then it is possible to know.
Besides, understanding does not require knowledge. As I said, it is about the ability to follow - logically - the way to draw conclusions from facts that you decide to accept as true.
For example - I can understand why someone who believes in the correctness of Islam's claims is willing to commit a suicide attack. It doesn't even mean that I believe in the claims of Islam and it certainly doesn't mean that I know that these are true claims.
If you can't know anything then all the more you can't understand, because in order to understand you need to know things.
anonymous:
A certain expansion of the concept of understanding is required for phrases like "I understand you" or "I understand what you mean" which discusses the ability to trace the process of drawing conclusions of another person or, at least, to know what his words mean.
point:
Do you know what you said?
Just unnecessary entanglement and twisting on such a simple and clear topic.
The things we know are few. Examples of what we know: while a person sees, he knows that he sees... this is the kind of thing we know. All the rest are beliefs/conclusions..
Simple and clear.
anonymous:
"Understanding" is the ability to prove the claim that one claims to understand through logical deduction from claims whose truth is accepted.
You can say that you understand (without lying) when you believe that you have in your hand (in your mind) proof as above.
And what about the concept of "understanding"
When will you be able to say that you understand?
Michael,
I will correct and refine my words. Mathematics can describe what happens in reality, even in an accurate way, but this legal description cannot be treated as an axiom either, because nothing is certain.
fresh:
You mix sex with non-sex.
I do not agree with Roy's claim that the math does not always match what is happening.
If the model corresponds to reality - the mathematics will also correspond. This, at least, is the basic assumption of the entire scientific enterprise.
A mathematical truth is indeed a truth, in my opinion.
but:
You refer to two sentences of Gedel and Shuga in their interpretation.
The incompleteness theorem means that in any consistent model (complex enough as necessary) there are sentences whose truth we cannot decide using its system of axioms - and this despite the fact that if the axioms are consistent - the sentences are true.
This does not say anything bad about the theorems that we can prove until the second theorem comes in which says - as you mentioned that we will never be able to mathematically prove the consistency of the axioms (the need to describe the natural numbers is complex enough) and therefore what we do prove with them is also questionable.
All this is true but irrelevant because there is one fact that can be based on and that is that in reality there are no contradictions, therefore if you have axioms that describe it correctly - these axioms do not contradict each other.
To be sure that our axioms are consistent - it is enough if we make sure that they are correct - in the sense of conforming to reality.
In fact - there is even a chance that the system of axioms necessary to describe reality will turn out to be extremely simple (one that does not need the representation of an infinite number of natural numbers) and then it will even be possible to prove its consistency.
On the other hand, all this, as Yehuda pointed out, does not help us because we can always question the axioms we choose to describe reality. The example of the virtual world you gave is actually an example of a failure in choosing axioms and not a failure in drawing conclusions.
In my opinion, there is really no possibility of really "knowing" things that are not tautological as long as knowledge is required to be true and certain.
The only way to refer to the word "knowledge" is as a word that describes a mental state of extremely strong belief.
Any attempt to tie the meaning of this word to the truth and certainty of knowledge is doomed in advance to failure.
Throughout our lives we are actually, intuitively, engaged in formulating probabilistic estimates for the correctness of claims and the details of the information we perceive with our senses make us come back to change and adjust our estimates and when the probability estimate is high or we tend to say that we know.
There are those who will claim that knowledge exists only when the probability we attribute to the claim is one and there are those who will claim that it is possible to settle for less - here we are entering a definition that in everyday language is not fully defined and any further discussion without a sharper definition will lead us to the paradox of stacking.
We do attribute certainty to the axioms of logic, but this is because our thought loses all meaning if we act otherwise.
We cannot know anything with 100% certainty, this claim is so strong that it also applies to itself...
In my opinion, in order to have a basis for the discussion of the theory of cognition, we need to differentiate between two concepts of knowledge, knowledge of 100% certainty which I believe does not exist, and knowledge of 99.9999% certainty that exists also exists but knowledge of 99.999% is not knowledge but only belief in my opinion, of course the root of the confusion is that some 99.9999% of the people think that it is news.
David Yom does talk about similar things and I'm sure he's not the first. Indeed, in the end, we must live our lives as if they were real, and therefore pragmatically, we cannot rely on the knowledge of 99.999% or any exosome and basic premise of one kind or another. Indeed, it is possible that there was nothing that started everything, that is, the thing that exists has no beginning. But in my opinion something must exist (and there is 100% certainty of its existence), whether it has a beginning or not. Because if all there is is nothing, then nothing really is nothing.
fresh,
The idea itself is ancient, and comes from the teachings of David Yum. But there is no proof in it of what is true or false. Godel proved it for mathematical theorems, but it should be remembered that mathematics is only a methodical way of describing the world, and does not always correspond to what is happening.
Ultimately, we must live our lives as if they were real.
And by the way, we also don't have to know for sure that there is something that started it all, because you are relying here on laws of logic that may not be valid, when logic itself is not an axiom.
All that has been said about the news is in trouble when the word "truth" is inserted into the definition of the news itself.
This is because it is impossible to know what is true and what is not. Because all the information given to us from the outside world is influenced by the interests of the information ethicists, by their worldview and position in relation to the event (the facts) so that everything can be biased one way or the other.
Since we cannot stand for the truth of anything with certainty, I think that the best definition of the concept of knowledge is a person's strong and whole-hearted belief in the truth of the information transmitted to him, when this specific person has no doubts about the truth of the information.
Godel does not prove that we are in a simulation and that nothing started it all, but he does prove that there are truth sentences that we can never prove to be true, that is, incompleteness in the sense that we can never know certain things only to believe that they are true or real. The same goes for the axioms of mathematics that we can never know if they are correct even though our subjective logic believes in their correctness. And of course this casts doubt on any mathematical development that is based on these axioms (doubt is a small one, admittedly, but still a doubt) For those who are interested in the subject, I recommend the book "Gedal Law and the Problem of the Basics of Mathematics" by Prof. Arnon Avron from the Department of Computer Science at Tel Aviv University.
It bothers me that they didn't give more importance in the article to the concept of uncertainty because in fact it doesn't seem to me that there is a fact that is absolutely true and without any doubt. In general, it is enough to look and see how a certain fact is certain for person A and not true for person B. For example the existence of God, heaven and hell, and of course the same for the one and only the dark mass.
Have a good week
Sabdarmish Yehuda
fresh,
Could you explain how Godel's incompleteness theorem proves the possibility that we live in a computer simulation, or that there is 'something that started it all'?
fresh:
What is certain that you do not know is the meaning of a grown sentence.
Not only do we not really know anything, but we don't even know we exist, maybe we are someone else's dream? Maybe we are a simulation or computer simulation of an advanced civilization, and maybe this advanced civilization is also a simulation of an even more advanced civilization, and so on ad infinitum. All we can know for sure is that something exists, the thing that started it all. A link to a scientist who supports this theory:
http://www.ynet.co.il/articles/0,7340,L-2082234,00.html
The incompleteness theorem of the famous mathematician Kurt Godel proves it.