Thanks for your question. I'd distinguish the undeniable claim that memory is fallible from the less plausible claim that memory is unreliable. I'm no psychologist, but it seems that the reliability of memory comes in degrees, depending on who's using it, under what conditions, and what its content is. The kind of remembering described in your question -- remembering what I was thinking just an instant ago -- doesn't seem especially unreliable, under favorable conditions anyway. Furthermore, we logically presuppose the reliability of memory in general even as we check whether some particular memory of ours is false: We ask those who are better-positioned what they remember, we trust that we correctly remember the meanings of words they use in their answers or the meanings of words we read in contemporaneous accounts of the event, and so on. Indeed, if we persist for any length of time in our belief that memory is fallible, that too depends on trusting our memory: it presupposes that we correctly remember that memory led us astray at least once in the past. So there seem to be limits to how sweeping any rational doubts about memory can become.

Thank you for these interesting reflections! As for your first point, there are a number of philosophers who address radical skepticism (e.g. can any of us know with certainty that we are not, as we seem to be, wide awake and acting in the world rather than, say, dreaming?) in the way you suggest. Arguably, life may continue just as it appears until one's death and yet there would be no decisive reason to rule out the possibility one was merely a brain in a vat. And because of this, some philosophers think that such radical skeptical hypotheses are idle or nonsensical or of no interest. I am somewhat of the other mind: I think we can imagine radical hypothetical states of affairs in which we are indeed systematically mistaken in almost all our beliefs about ourselves in the world (in brief, I think it conceivable that we might be in the matrix). While this does not have awesome practical consequences, I think it should humble us in our knowledge claims. As for the second point, Quine set out to dismantle the very categorical distinction between the analytic and synthetic. Today, some think he was spot on, but there are large numbers of philosophers (including myself) who believe the analytic category is sensible and intelligible. I think it is an analytic truth that 1+1 equals 2 --based on the principle of identity or A is A (because 2 simply is '1+1' and so 1+1 equals 2 because 1=1 equals 1=1. You ask about explanations. On that point, things get quite interesting. The concepts of necessity, impossibility, and possibility can be explained in terms of one another. So the statement '1+1 = 2 is necessary' is equivalent to '1+1=2 is possible and 1+1 is not equal to 2 is not possible. To many of this, explanations like this are acceptable, but to some radical thinkers, such explanations are considered insufficient. For a great defense of the analytic category and the concepts at issue, check out Alvin Plantinga's classic On The Nature Of Necessity.

While Ayer's verificationism has gone out of fashion (he and others could not settle on a formulation of it that did not rule out science or some such apparently meaningful discourse) there are forms of what is called anti-realism which define 'truth' in terms of warranted assertability, which would rule out the possibility of there being truths that are out of reach from what we can know (at least in principle). Alas, there is a good argument against such a position in Thomas Nagel's work The View From Nowhere.

One other idea to consider is that your friend may be right but in a way that has nothing to do with THIS (our) world. Some philosophers (David Lewis etc) have argued that there are indefinitely many POSSIBLE WORLDS. So, you might reply that, yes, leprechauns actually do exist but in a possible world not remotely related to ours! Check out Lewis's book on the plurality of worlds. It is awesome.

Just because God knows what is going to happen does not mean it has to happen, in the sense that human beings have to do what they end up doing. For example, I always have sugar in my coffee, if sugar is available, but that does not mean that I am incapable of having coffee without sugar. I used to smoke after a cup of coffee, but no longer do so, and here again I did not have to give up smoking. God doubtless knew what I was going to do before I did it, but the decisions to use sugar, and discontinue smoking all belong to me.

Much depends on what you mean by "the analysis of knowledge." I assume that you mean the attempt to explicate the respect in which knowledge is more than mere true belief, an enterprise that goes back to Plato's Meno. It seems to me that you think that discussion that attempts to fill whatever condition is necessary for knowledge besides mere true belief fails to make contact with what we care about when we care about knowledge. But even that discussion, I submit, seeks to capture the respect in which knowledge is valuable. Apparently the methodology by which this investigation has been conducted doesn't appeal to you--you seem to have doubts about the appeals to intuition in this context. While much ink has been spilled about the philosophical significance of intuitions, it does seem plausible that if one is to try to capture what is distinctive about knowledge, it is at least helpful to begin with clear-cut cases of the phenomenon as a starting point. And it seems to me that the ultimate aim of the enterprise--determining the nature of knowledge--is valuable indeed. Perhaps it will help you appreciate what is at stake in such debates to reflect on the significance of knowledge, which I think ultimately underwrites them.

Questions should be understood contextually. In your story about John, we are led to assume that John is about to drink the contents of the glass, and not, for example, use it in a chemistry experiment requiring high levels of purity. The suggestion is that it is water and not e.g. orange juice or beer. A small amount of harmless impurities don't make any difference to its drinkability-as-water. A tiny amount of cyanide, however, makes all the difference in the world to its drinkability-as-water. It's not the amount of impurity that matters, its the difference the impurity makes to our intended use of the water. (This is a case that shows the pragmatic functions of language. Sometimes you miss things if you take language "too literally" i.e. devoid of context.)

To begin with a slightly pedantic point: logic doesn't actually give us very much knowledge at all. Logic tells us things like that, if A is true and B is true, then A & B is true. But, in order for us to be in a position to draw that conclusion, we first need to know that A is true and B is true. And, for most ordinary As and Bs, logic isn't going to tell us that. We need to turn instead to our senses. We have five external senses -- sight, touch, hearing, smell, taste -- which tell us about the qualities of objects in our environment. And, if we use these in a cautious and regimented way, and maybe start to draw logical inferences once we do first have the raw data to work from, then we can achieve an awful lot of knowledge.

But now to turn to your question: can meditation give us additional knowledge, besides that which we can get through the external senses? Yes, it surely can. Meditation can teach us what it feels like to meditate. Indeed, it might enable us to know quite a lot about our own internal psychological states. We usually don't pay a whole lot of attention to our own psychology... except when we make a deliberate effort to meditate upon it.

But can meditation operate as some kind of 'sixth sense', to give us knowledge about things outside ourselves? Frankly, I doubt it. That's an empirically testable hypothesis, after all, and I'm not aware of any studies that suggest that meditation can do this.

Some recent papers by the psychologist Daniel Kahneman suggest that we are not very good at predicting what will make us happy. It is a good idea to read these to get a feel for human fallibility.

Philosophers often argue that reflecting rationally on our values and goals can lead us to pursue what we "really" want, and thereby lead to greater satisfaction. You might try this and see whether it helps.

Some Buddhists, and some psychologists, argue that pursuit of a goal is more exciting than achieving it. They suggest focussing on the activity rather than the desired result.

Some recent papers by the psychologist Daniel Kahneman suggest that we are not very good at predicting what will make us happy. It is a good idea to read these to get a feel for human fallibility.

Philosophers often argue that reflecting rationally on our values and goals can lead us to pursue what we "really" want, and thereby lead to greater satisfaction. You might try this and see whether it helps.

Some Buddhists, and some psychologists, argue that pursuit of a goal is more exciting than achieving it. They suggest focussing on the activity rather than the desired result.

There's a lot of interest here, and a lot that's problematic in your questions! ... There are empirical studies in the U.S. at least that show things such as that college degrees increase average earning power over the course of your life -- now whether that means 'the more knowledge you have' leads to 'more success and happiness' I don't know, but it's the kind of statistic that might be relevant to your concerns .... I am not inclined to think that (all) knowledge is 'produced just to be sold' -- it's produced for many reasons, including the inrinsic interest of producing it -- but if it turns out that (much) knowledge is in fact useful, and valuable, then why would it be surprising that it would also be sold, even if it isn't produced for that purpose? Now if you're concerned about more political/sociological issues -- like what sorts of societies choose to have their education be so expensive, etc., that I can't say -- I too would prefer that education be far less expensive, be seen as a public right and not a privilege etc., but then that becomes an issue for politicians and not for philosophers ...

hope that's useful --

best, ap

p.s. the philosophers on this site don't get paid anythign for participating -- so not ALL knowledge is sold! :-)