My first reaction was that you must be rather different from me, because I sure don't hear my voice when I'm not speaking. But on inspection I find that I can of course imagine myself speaking (actually I find it works better for singing), which is at least a lot like hearing my voice in my head without speaking. But this is no more mysterious than the fact that I can imagine other sounds without actually hearing them, or that I can remember sounds without hearing them at that time. Just what the relationship is between the neurophysiology of imagined or recalled sound and the neuorphysiology of hearing is an interesting question for the scientists to answer.

Nice question. I guess it depends on how good the joke is. No, seriously, your question is a good riff on what seems to be the non-philosophers’ paradigm of a philosophical question, namely, ‘If a tree falls in the forest and there is nobody there to hear it, does it make a noise?’. I have to confess that when I first heard this I wasn’t at all sure what philosophical question it is asking, but I now take it that it is a question about the nature of sound. Is sound really just the experience of sound? Then if there is nobody around, there is no noise. But if sound is say really vibrations in the air, then the forest is noisy even when nobody is around. So what is nature of funniness? Maybe a joke is funny if it has the disposition to make people laugh. One consequence of this view is that jokes are funny even when they are not being told, because the disposition is there even when it is not being manifested. It’s just like pipe cleaners, which are flexible even when they are not being bent. So on this...

I don’t think that the moral of your story would be that being right is just being in the majority, but it might be that we can’t know whether or not we are right. But even this fortunately won’t always be the case. Even if I can’t convince you, I may have good reason to believe that I am in a better position to know, because I have better evidence, because I am more expert in the area of our disagreement, etc. But the tough case is where we disagree and I have no reason to think that I am better placed to be right than you are. And this does seem a common plight when the disagreement is in philosophy, though it is by no means limited to that area. Suppose that Hilary Putnam and I could lay out all the arguments that either of us can think of on some philosophical issue – say the existence of numbers – and still we end up disagreeing. It seems to me on balance and after much reflection that (say) numbers don’t exist, and it seems to him likewise that they do. What am I to do? Not only do we disagree,...

Like most philosophers (though perhaps not most historians and sociologists of science), I think that knowledge requires truth, but it remains possible for someone to know something at one time and not to know it at a later time. Knowledge requires belief as well as truth, so a simple way that knowledge can be lost is if a person knows something but later for whatever reason stops believing it. Knowledge also requires warrant, and warrant may be lost. One possible example is where the warrant is forgotten. Suppose I prove a mathematical theorem. At that point I know that theorem to be true, but later I forget not only the proof but that I ever had a proof, though I retain the belief in the theorem. Here I would say (though I can imagine some philosophers resisting this) that I no longer know. Or maybe I don’t forget the warrant, but I acquire additional evidence that goes against my belief. Thus suppose I remember the proof, but it was quite tricky, and one day a much better mathematician that I...

Philosophy does not have a distinctive method. The subject is better characterised in terms of the problems it addresses than in terms of the methods it uses. But in philosophy we do often find ourselves in the situation where the question seems genuine but there is no straightforward procedure for answering. (Some might even be tempted to define a philsophical problem in this way: real questions with no clear way to determine answers.) The questions seem neither straightforwardly empirical, nor susceptible to anything like proof. So we scrabble around as best we can, clarifying, articulating, and checking for consistency and coherence.

Mach was a 'neutral monist', which means that he held that the fundamental units of reality are neither mental nor physical, but when they are combined in some ways they form minds and when they combined in other ways they form physical objects. He was not a solipsist, since his position allows for the existence of many minds, and perhaps even for the knowledge of their existence. By the way, even if you can't refute solipsists, it is some consolation that you can be certain that if they exist they are mistaken.

This is a good question. I gave the lost keys analogy as part of a reaction to the pessimistic argument that since past scientific theories have turned out to be wrong then its likely that present scientific theories will turn out to be wrong as well. My reaction is that we may be learning from our mistakes and indeed we cannot discover the truth immediately but must try things out and eliminate what turns out to be mistaken. In this case, a history of false theories does not show that present theories are likely to false; indeed it may make it more likely that they are true. But what if there is no key? Your point I take it is this. Sure, if we know that one of a group of competing theories is correct, and we can rule some of them out, then this will increase the probability that one of the remaining theories is true. But maybe none of the theories we consider is true. In that case, no amount of elimination will expose the truth. Clearly, if no theory we will...

Let’s start with a different case. When you see a mountain, you see an object miles away, even though the visual experience is in your brain. The mountain doesn’t have to go into your brain (thank goodness) in order for you to see it, because the brain can represent the external object.The case of the pain in your hand is not exactly the same, but here too it seems that one thing (in your head) is representing another thing (in your hand). Perhaps it is stranger to suppose that we represent something outside our head as having pain that that we represent something outside our head as having the shape of a mountain, but something like that seems to be what is going on. And this may seem less strange in light of the fact that we know anyway that we have the power to represent things that aren’t actually there, for example in a case of hallucination. So the fact that the pain isn’t actually in our hand does not mean we can’t perceive it as being in our hand.I don’t want to sound complacent. ...

One aspect of success is getting what you want, so if Mr. A wanted knowledge, and he got it, then he was successful. Indeed getting what you want is an aspect of success even if you don’t realise that you are getting it. For example, if I want to be a good role model for my children and I am, then I am successful, even if I mistakenly believe that I am a terrible role model. So even if Mr. A doesn’t realise that he is getting knowledge, if he is then he is successful. But maybe it’s not enough for success to get what you want; maybe what you want also has to have some value other than the value of being wanted. For example, some people would deny that a person who has managed to collect an enormous number of used matches is successful, even if that is what he wanted to achieve, on the grounds that what he wanted has no value. I’m not convinced that this is right – I think maybe the bare fact of wanting something gives it some value – but if one does accept the need for intrinsic value, then...

The good news is that this feature of after-images seems no more difficult to explain than how we see physical object like a table 'out there'. True, there is an actual table out there while there is nothing corresponding to the after image out there, but this makes no difference. In both cases, something inside our head is managing to present something as out there. (Fortunately, the table doesn't come into our heads when we see it.) So I think your question is just how the brain or the mind manages to see things as outside itself, whether there really are those things out there or not. The bad news is that we really seem to have no idea how this is possible (which is not to say that philosophers -- including notably Immanuel Kant -- haven't spent a lot of time worrying about it).