I have two questions about logic that have vexed me for a long time. Smith has written two great books of philosophy. Now he has come out with a third book. Therefore, that book will probably be good too. Smith has flipped a coin twice, and both times it has come up tails. Now Smith will flip the coin a third time. Therefore, that flip with probably end up 'tails' too. The logical form of inductive arguments seems to contribute nothing; the premises seem to do no logical work supporting the conclusion - is that right? Smith has written two great books of philosophy. Now he has written a third. Any author that has written two great books of philosophy, and then writes a third, has probably written a third great book. Therefore, Smith has probably written a third great book. That seems a deductive argument, because the general premise was added. And if true, the premises do seem to support with conclusion with necessity, even though the conclusion is probable; it is the knowledge of the world and not...

I think both arguments can be analyzed as inductive arguments and still distinguished in terms of their quality. The book argument is a stronger inductive argument than the coin-toss argument for a simple reason: the probability that Smith's book C is great isn't independent of whether Smith's books A and B are great. That is, Smith's having written great books A and B makes the probability that Smith's book C is great higher than it would be had Smith not already written two great books. Important: higher than it would be otherwise, which needn't mean higher than one-half. Even though Smith's track-record raises the probability that book C is great, the track-record needn't make it more probable than not that book C is great. By contrast, the probability of tails on any given toss of a fair coin is independent of whether the coin came up tails twice already: that history of tosses neither increases nor decreases the probability of tails on a third toss.

We know for now, at least, it's impossible to go back in time scientifically. But what if you really needed to, say if you had done something really bad and had ever desperation to go back in time and correct what you did, so you don't suffer the consequences you are suffering in the present. Provided you would not cause a disaster by going back in time, and that you would only change the bad things you did, it is an interesting concept. With this context, if you could be given a drug, that would leave you asleep for the rest of your life (coma), would you do it? Read on, there's more. In this sleep, you will have a dream, which is set from just before your mistake. So essentially, it causes you to simulate the past and the rest of your life in your head. It seems real, but it isn't. My question is, would this be the same as going back in time and changing things in reality? Does reality matter more, or our interpretation of it?

First a terminological quibble. By "scientifically impossible," I take it you mean "technological infeasible," i.e., impossible given the limits of current technology. As I see it, what's scientifically possible or impossible depends only on the laws of nature, which are standardly taken to be unchanging over time (or at least over any time that humans will experience). I think the jury's still out on whether backward time-travel is scientifically impossible in this latter sense. To your question: I think there's something self-contradictory in the idea of "correcting what you did" if that means "bringing it about that you never did what you in fact did." Either (1) you did it, or (~ 1) you never did it. I can't see how any consistent story features both (1) and (~ 1). In that sense, then, there's no such thing as (2) "going back in time and changing things in reality" and therefore nothing that's the "same as" (2). See section 1.2 of the SEP article on time-travel .

Is it consistent to be a libertarian while opposing suicide on moral grounds?

I'm no expert on libertarianism in political philosophy, but I think I can answer this one: Yes. As I understand it, political libertarianism is a position concerning the legitimate power of the state. One can consistently oppose suicide on moral grounds while maintaining that the state has no business interfering with suicide. One can consistently think that, for various reasons, one morally ought not commit suicide while also thinking that the law should keep out of it. Indeed, a particularly strong distinction between "immoral" and "illegal" seems to lie at the heart of the libertarian outlook.

Are the laws of logic invented or are they independent of human reason? If they are independent, how can they exist immaterially? What does it mean for such laws to exist in a nonphysical way?

Good question, and as fundamental a question as anyone could ask. I think that the laws of logic must be not only independent of human minds but independent of any minds, including God's mind if such exists. At any rate, I don't think anyone can see how it could be otherwise. To say that the laws of logic depend on human or divine minds is to imply that the following conditional statement is nontrivially true: If (1) human or divine minds had been different enough, then (2) all of the laws of logic would be different from what they are . (By "nontrivially true," I mean that the statement is true not merely on the ground that (1), its antecedent, is logically impossible. If (1) is logically impossible, then the conditional statement is trivially true, even if (2), its consequent, is also logically impossible.) We can't make sense of the italicized statement without presupposing that (2) is false . If the italicized statement means anything, then it doesn't mean this: If (1) human or...

In several answers in AskPhilosophers, philosophers say that some uttered words express emotions, feelings, sensations and the like (but you always use the word "express"), and that this is not the same as some words saying or stating that such emotion (etc.) occurred. So you make a big difference between expressing and saying (or perhaps stating). For instance, "ouch" expresses pain, while "I am feeling pain" states that such pain exists. Sometimes you say that expressing cannot be true or false, but statements can. It is very difficult for me to understand this difference. I understand that "ouch" is much more immediate than "I am feeling pain", and that "ouch" is slightly humorous, and there may be other differences, but basically these two sentences just say the same thing. They convey the same basic information and both can be used to give a false information. Would you be so kind as to explain me what is the difference between expressing and saying (stating) in cases where what is expressed can be...

A very interesting question touching on complicated territory! Probably the best response I can give is to recommend the SEP article on "Pragmatics," available at this link . I think you'll find it contains lots of information highly relevant to your question.

In the light of the current state in philosophy, do skeptics still get an upper hand? Can we really know anything with certainty?

I'm going to refer you to two websites. At the PhilPapers Survey , you'll discover that only 4.8% of "target faculty" said that they accept or lean toward skepticism. Among specialists in epistemology (the theory of knowledge), that figure increases to 9.4%, but it's still small enough to suggest that philosophers in general don't think of skepticism as having the upper hand once the reasons for and against it are examined carefully. For detailed discussion of your second question, you might start with the SEP entry on "Certainty" . I hope you find these resources helpful.

Friend A believes Friend B should try something before deciding not to like it. Friend B believes he shouldn't have to try something if he doesn't want to. Who is correct? Are they both correct? Who is more correct? Should Friend C help convince Friend B to try the thing or let him make his own choices?

I hope I don't come across as pedantic, but I think that your questions may contain what philosophers call "false alternatives." First, there's a sense in which both A and B can be correct. It might be that B is well-advised to try a particular something before rejecting it because the risks associated with trying it are small compared to the possible benefits. Nevertheless, it could be true that B "shouldn't have to " try something before rejecting it: that is, B might well have the right to refuse to do X even if he would be well-advised to do X. Second, C can help convince B to try the thing even while C lets B make his own choice. As I see it, giving B convincing reasons to make a particular choice needn't mean depriving B of a choice -- including a free choice -- in the matter.

When the word" exist "occurs like "numbers exist "does it mean what it means in sentences like "Dogs exist"?

I think it does, or at least I think the burden of proof is on anyone who says that "exist" is systematically ambiguous, meaning one thing when applied to numbers and another thing when applied elsewhere. It's widely held that abstract objects such as numbers, if indeed they exist, don't exist in spacetime, whereas concrete objects such dogs clearly do exist in spacetime. But that doesn't affect the meaning of "exist" itself. In particular, it doesn't imply that "exist" means "exist in spacetime." Otherwise, the expression "exist in spacetime" would be redundant and the expression "exist but not in spacetime" would be self-contradictory, neither of which is the case. Analogy: It's a fact that some things exist aerobically and some things exist anaerobically, but that fact doesn't tempt anyone to say that one or the other kind of thing doesn't really exist, or to say that "exist" just means "exist aerobically." So I see no reason not to say that numbers, if they exist, exist nonspatiotemporally,...