In a debate about faith and doubt in which I was doubting all existence and my friend argued in favor of existence, he challenged my rationalistic perspective by asking me this: Your reasoning depends upon the rules of logic, but there is a problem: how do you KNOW, conclusively, that the rules of logic are sound? Isn't that an act of faith? Can't you conceive of a universe in which logic *appears* to work, but in which logic is actually an illusion? How do you know that you don't live in that universe? Cogito ergo sum did not cover this one. I was stumped. Can you help me out?

Also, if I were to tie your hand behind your back and then ask you whether you can touch your nose with it, that would be a peculiar question. And something similar is going on when one's asked whether one can defend all one's principles of reasoning. The whole practice of defending something assumes that principles of reasoning are in place. In fact, a cogito -like situation is indeed present: a state of affairs holds (thinking, defending) which demands presuppositions (existing, acceptance of rules) that make a certain doubt (about existence, about logic) self-stultifying.

I was thinking about Zeno's paradox of motion today and decided on an explanation that I'd like to check. As I've heard the paradox stated, one premise is that in order to get from A to B you have to first get to the midway point, call it C. Then there are other premises resulting in the conclusion that motion is impossible. But doesn't the above premise already allow for the possibility of motion, making you agree that motion to C is possible before going on to claim that motion to B is not? Perhaps there is another way to state the paradox, then? Thanks much.

Right, so it seems you think the argument is self-undermining. It assumes that you can get to the midpoint, C, and then it goes on to prove that motion from C to the endpoint B is impossible. Maybe we need to rethink our assumption that we could get to C! And indeed, other versions of this paradox of Zeno's work in that way. In order to get from A to B, this version runs, we need to get to the midpoint C. But in order to get from A to C, we need to that interval's midpoint, C1. And in order to get from A to C1, we need to get to its midpoint C2, ad infinitum . The strategy is always the same: to find a way of taking something finite (in this case, the racetrack) and dividing it into infinitely many parts; then arguing that a related task (here, running to the finish line) that looked to be finite really involves an actual infinite number of subtasks (here, reaching all the midpoints); and then concluding that, because one cannot complete an infinite number of tasks, the...

Are statements about probability universal truths? Is it possible to conceive of a universe in which a fair coin lands heads 75% and tails 25% of the time?

In answer to the question, whether a fair coin's flips might approach 75% heads and 25% tails, I'd like to say No. For the trivial reason that approaching 50% heads/50% tails is just what we mean by "fair coin."

What makes a person a Philosopher? I have to write a paper asking any Philosopher in history, dead or alive, two questions. I'm just curious as to what a Philosopher is. Is it a self-proclaimed title? Do you have to go to school and get a degree? Can I just find any random person who claims to be a Philosopher and assume they know what they are talking about? What about Jesus? Does he count?

Easier asked than answered. Philosophers are people who do philosophy, and so your question really amounts to what philosophy is. The problem is that what philosophy is is itself a philosophical question. Many grand disputes in the history of philosophy can be viewed as conflicts over how to proceed in philosophy, over what the rules of the game are, over what philosophy's method and central problems ought to be. So, I suppose one "definition" of philosophy might simply be the discipline which takes as its subject its own nature . Of course, that has a circular whiff about that as well. Philosophy is a little like pornography: hard to define, but one knows it when one sees it. But really, most concepts are like pornography in that respect: there's pretty widespread agreement about how they apply, but little hope of working out independently intelligible definitions. That fact itself is something of great philosophical interest. But don't ask me to define precisely what I mean...

Wittgenstein said that anything that can be said can be said clearly; how should we view this contention in light of the fact that Wittgenstein's own writing is famously enigmatic (or at least aphoristic)?

That's a good question and a really good answer would have to involve getting into the details of Wittgenstein's thought. But perhaps one thing that might be said at the outset is that saying something clearly and saying something that's easy to understand are not the same thing. A good textbook in advanced mathematics contains many clear statements – but that doesn't mean it's easy for anyone to understand them. Whether something's easy to understand depends in part on the clarity of the thought's expression, but also on the subtlety or complexity of the thought being expressed.

When discussing whether Homosexuality is morally right or morally wrong, I've always argued that if we allow homosexuality then we would have to allow incest as well. Before arriving to this conclusion I first looked at the various arguments defending homosexuality which mainly consisted of the following: 1) It's consensual (with the exception of rape); 2) It doesn't harm anyone; and 3) It's a matter of love (i.e., we should have the right to be with whomever we love). Now my reasoning is this: All three of those arguments could be used to defend incest! Imagine a father who becomes sexually involved with his 20-year old daughter. Both would be consenting, they are not harming anyone, and they presumably have some type of attraction towards each other. My question is if my argument is a good one or am I missing something?

First, there's a difference between showing that an argument for permitting homosexuality is bad and showing that homosexuality shouldn't be permitted. To show the latter, you need an argument to that very conclusion; it won't do to show that some argument for permitting homosexuality is actually a bad argument. Refuting an argument in support of X is different from giving an argument for not-X. Second, I'm not sure you succeed in even showing that the argument you consider for permitting homosexuality is a bad one. You want to say that if the argument were correct then it would also permit incest; since the latter shouldn't be permitted, something must be wrong with the argument. But I'm not sure I agree that the argument you consider about homosexuality really would also apply to incest. That's because I think that incestuous relationships do often lead to psychic harm for one or both of the individuals involved (as opposed to homosexual relationship, which don't lead to such harm – at...

Presently I am a first year philosophy major and I am interested in taking an Introduction to Symbolic logic course next year. However, I am worried that since my background in math is very weak, taking that class would just be torture for me. I was wondering how math-dependent is symbolic logic? I recently studied the informal and formal fallacies in an ethics class which I found to be easy...does that mean anything? Thanks in advance for the reply.

I would say that a well-taught first course in formal logic would presuppose no mathematical knowledge and no mathematical sophistication. The material is technical in nature and freely employs symbols and terms drawn from the vernacular of mathematics -- but all these should be explained by your instructor. From teaching this material many times, I know that some "math phobic" students freeze up at the sight of parentheses and greek letters. But I always tell them that these symbols are their friends! They serve to make our lives easier by allowing us to say just what we want to say very briefly and perspicuously. We could in principle do without them -- but that would in fact make our lives a lot harder.

I am curious: What are some questions of the philosophers? Alexander George, Noga Arikha, Amy Kind, Thomas Pogge, etc., we see your names, but we do not know your own inquiries. It would be novel to read and ponder the questions of those brave enough to answer our questions. And might one also learn by extrapolation, by thinking about a question new to them?--that is, the site can remain educational by shedding new light on a dim part of philosophy: the branch of asking questions. I would like to see a list of questions posed by the panelists.

I'm not so confident that perusing a panelist's publications will helpthe layperson see which questions animate the philosopher. Those publicationsusually begin far into a long conversation and it might be hard to find in themthe simple questions that kicked off the discussion in the first place. So I'll place one on the table. I'd love to have a satisfying answer to this question: "What are we saying when we claim that 5+3=8?" Ilike Thomas' suggestion though. I'll start: I'm not sure I understandwhy many colleagues are as convinced as they are that work in empiricalpsychology is relevant (if not central) to many long-standingquintessentially philosophical questions. It seems to me that the 20th Century saw a number of subtle criticisms of this conviction that have been more ignored than answered. (I'm not assuming its irrelevance. I'm just puzzled at times by the confident, or at least untroubled, assumption of relevance, especially in the face of powerful dissents.)

I’ve run into a problem in philosophy recently that I do not completely appreciate. Certain sets are said to be “too big” to be sets. In Lewis’ Modal Realism, the set of all possible worlds is said to be one such set. These are sets whose memberships is composed of infinite individuals of a robust cardinality. I (purportedly) understand that not all infinities are equal. But I don’t quite see why there can be a set of continuum many objects, but not a set of certain larger infinities. Am I misunderstanding what it is to have “too big” a set?

When a set theorist says that such and such collection is "too big" to be a set, what he typically means is that if that collection were taken to be a set a contradiction would arise. The collection of all sets is such a collection. If we assume it's a set then, applying the argument that generates Russell's Paradox, we arrive at a contradiction. And so we conclude that we were wrong to assume that the collection of all sets is a set. As set theorists put it, it's a proper class , not a set. Is there any way of telling whether a collection is "too big", i.e., a proper class, or whether it's a set, besides seeing whether the assumption that it's a set leads to a contradiction? No. So really, "too big" is just a colorful way of saying "leads to a contradiction if assumed to be a set".