It is worth commenting further on that idea that "everything we do has an egoistic motive". We need to distinguish here a truism from a falsehood. The truism is that, when I act, it is as a result of my desires, my intentions, my goals. After all, if my arm moves independently of my desires, e.g. because you want it to move and push it, then we'd hardly say that the movement was my action (it was something that happened to my body despite me). But even if everything I genuinely do (as opposed to undergo) is as a result of my desires etc., it doesn't follow that everything I do has an egoistic motive. For to say that I do something for an egoistic motive is to say something about the content of my desires -- i.e. it is to say not just that the desires are mine but that the desires are about me or directed towards me or something like that. And it is just false that all my desires are like that. I can want to bring about states of affairs in which I just don...

Well, it is certainly true that introducing unambiguous, very carefully defined, agreed terminology and having a perspicuous notation can make reasoning easier and make us less prone to common reasoning errors. To take the obvious example, mathematicians aren't just being awkward when they use a lot of symbolism and make very careful distinctions wrapped up into technical terms (and borrow from the languages of formal logic to make clear, for example, the 'scope' of their quantifiers). If proofs all had to be written out in unaugmented English, then we'd get lost following them, even in elementary high school algebra: and proof-discovery would be orders of difficulty harder. I suppose we might say "mathematicians' English" -- meaning English augmented with their new definitions and notational devices -- is a new, better, language, more suited to (mathematical) reasoning than street English. But equally, we might say that it is just one part of a single inclusive language, modern English: it is just a...

Why shouldn't two different chains of reasoning lead to one and the very same conclusion? Mathematicians often give different proofs of the same result. For example, Aigner and Ziegler's wonderful Proofs from the Book starts off with six proofs (chosen from many more) of the same proposition, i.e. Euclid's result that there is an infinite number of prime numbers. The very different routes to the same conclusion are illuminating, as they show up different connections between the fact that there is an infinite number of primes and other mathematical facts. But it is one and the same mathematical proposition that the different connecting proofs all home in on. I've chosen a mathematical example first because of the question's emphasis on "logical reasoning". But the point generalizes to cover other sorts of grounds we might have for accepting a proposition. I take it that Jill is in the coffee bar, as she has just phoned me and told me she is waiting there for me right now. You take it ...

Having an office? But really, this is the wrong question. There's no such thing as an "official philosopher". There are just people now writing on philosophical issues whose work is taken more or less seriously and is respected by other people seriously working on philosophical issues. True, nearly all of these people are employed professionally as teachers and/or researchers by universities, and hence have offices! -- so I suppose they might be said to be "official" in an uninteresting sense . There are not many these days who are like Bertrand Russell with a private income. But of course it isn't that sort of professional status that matters about a philosopher, but whether they are any good. So what makes it the case that this writer's work is taken more or less seriously and respected, and that writer's work isn't valued so much? I think I can recognize good philosophy, and hence a good philosopher (I have to say that, having edited one of the philosophy journals for a long time). But...

There is a number of different issues here. Let me comment on just one of them. We may indeed wonder how people, in certain situations, can come to act in appalling ways. The question as asked perhaps suggests that arm-chair philosophy might help in understanding this. But not so. This "how come?" question is an empirical one. What is needed is e.g. a knowledge of empirical work in social psychology, such as the Milgram experiment , which explored the willingness of subjects to inflict (apparent) suffering at the behest of an authoritative figure. The results of such work are highly alarming but also, I take it, highly salient for the historian. For they suggest something of the ready possibility of authority structures that might facilitate widespread evil behaviour. We can oh-so-easily be led to do terrible things.

I wonder what is meant in the question by talking of philosophy as a self-perpetuating field ? In what sense is philosophy supposed to be "self-perpetuating" while biology isn't? Perhaps the idea is supposed to be that philosophy is self-perpetuating because, unlike biology, it just goes round in circles for ever and never settles anything. If that is the implicit claim, then I think it should be resisted vigorously. It would be just absurd to deny that we now know a vast deal more about issues about language, meaning and reference than we did before the time of (say) Frege; it would absurd to deny that we now know a vast deal more about the nature of the mind than we did before the time of (say) William James. Again, think about the philosophy of space and time: it would crazy to suggest that we are stuck where Newton was. And so it goes, through area after area. Of course, "settling a question" in philosophy isn't exactly like settling a question in biology (though that too, as the...

Allen Stairs rightly queries the claim that the foetus is already a new person: killing an early foetus is not straightforwardly killing a person -- it is at most killing something that would otherwise become a person. Still, you might be tempted to say -- indeed, many people do say -- killing a potential person is as bad as killing a fully-fledged person. Well, I disagree. But just asserting a disagreement is hardly very interesting. So what sort of grounds could I give to support my position? What sort of grounds could you give for yours? At this point, we might be tempted to bandy about very general principles about the morality of killing or the "right to life" which are supposed to settle things one way or the other. Now this might help. But more likely, it will just shift the debate from a clash of intuitions about abortion to a clash of intuitions about these more general principles about killing and we will find ourselves going around in circles. What to do? Well, I...

1. Once upon a time, I guess that quite a few philosophers thought that a one-shot bash with (something like) the verification principle was enough to dispose of various claims of religion. These days, few philosophers think there's such a quick route to declaring some area of discourse "cognitively meaningless". 2. My impression remains however that many philosophers do think that various kinds of religious claims haven't got a clear meaning at least if interpreted flat-footedly, as making metaphysical claims about the contents of the universe. Take the words of the catechism: "God is the Supreme Spirit, Who alone exists of Himself and is infinite in all perfections". What does that mean ? The complaint is not the quick one that it is "unverifiable", but the more laborious-to-defend one that trying to work out some metaphysical content to e.g. "infinite in all perfections" leads to confusion and paradox. But there are certainly philosophers who think that a coherent metaphysical story can be...

To understand "the philosophers and their theories" you have to understand what philosophical questions were bugging them -- and understand the arguments they give for their theories (since the theories are worth no more than the arguments that support them). So it's not a really an issue of where to start, philosophers vs. questions. It's more an issue of whose list of questions to start with. An agenda set by some of the great dead philosophers? Or an agenda set by a class of students? Or perhaps somewhere in between -- an agenda set by the author of a good introductory book (like Simon Blackburn's Think ) which raises questions that look likely to have immediate "relevance" to the students, but which relates some of the responses and arguments to those of the great dead philosophers? In general I'd go for the third option. I certainly wouldn't go for the first.

Three examples to think about. First, Frege's invention of the predicate calculus was driven by philosophical reflection on the nature of quantified propositions, and led in turn to modern mathematical logic. Second, the so-called Hilbert programme was driven in part by more philosophical reflection, this time on the limits of what we can directly "intuit" to be mathematically correct; that programme led in turn to the development of modern proof theory. Third, Kurt Gödel's philosophically driven work on set theory was mathematically hugely important. [Sorry, those reference links are inevitably to material that quickly gets mathematically heavy!]So, it surely is the case that specific philosophical ideas -- philosophical reflections on foundational matters -- have influenced the development of mathematics. And one might say too that a more general set of philosophical ideas about the proper nature of mathematics drove the whole Bourbaki project which has been so influential in the...