A logically valid argument is one that has the property that, if its premises are true, then its conclusion must also be true. It's a nice question how exactly one wants to spell that out, but if we play along with the talk about "possible worlds", then we can say: A logically valid argument is one that has the property that, if, in any given world, its premises are true, then, in that world, its conclusion must be true. On that understanding, the kid's argument is logically invalid. True, there are some worlds in which everything the kid's father says is true. But that is not enough. For the argument to be valid, this has to be so in all worlds, and it obviously isn't. I think the confusion here may be caused by the phrase "always...invalid, in every possible world". Validity is preservation of truth in every world. But what happens in every world isn't really affected by which world you are in, so talk of what's valid in every world doesn't really make sense. What's valid in one world...

Let me add a few words to Sean's excellent response. I think one thing worth keeping in mind here, which I may have said already in response to a similar question, is that the institution of marriage in the United States, and in some other places in the developed world, has changed a great deal over the last sixty years or so. A friend of mine once joked, "Of course marriage has to be between a man and a woman. Otherwise, how would you know who gets to beat up whom?" Not very funny, of course, in one sense, but perhaps you see her point. There was a time, not very long ago, when it was legally impossible in many states for a woman to be raped by her husband. A married woman's ability to own property independently of her husband was curtailed in some jurisdictions. Men had, by law, that kind of control over their wives, and the entire institution of marriage was one of ownership. That is why many radicals of the Victorian and post-Victorian eras were deeply suspicious of the entire institution...

I guess you're talking about "Real Dolls" and the like, of which Howard Stern seems to be such a fan. The terms in which you describe this debate seem to me to be highly contentious. I really do not understand why the question whether someone is "socially challenged" or "sexually frustrated" has anything to do with it. I think the sensible, default viewpoint would be that, if someone wants to masturbate, then they should be free to do so in whatever way they choose, either alone or with their partner or whatever. And if they enjoy using sex toys, then they should be free to use them, too. If one of the sex toys they like to use is a "love doll", either of the blow up variety or the incredibly expensive "Real Doll" variety, then so what? Maybe they like to fantasize about making love to super models, and maybe the doll helps with the fantasy. Great! Feminists like Nancy Friday worked very hard to earn all of us, men and women, the right to such freedom. That said, "so what" could have an answer,...

This problem, of the "tyrrany of the majority", is a very old one in political theory, and it is also one of the major practical problems every democracy must negotiate. Theoretically and historically, its solution lies in the emergence of what are sometimes called "liberal democracies". The term "liberal", in this usage, is not as opposed to "conservative" but rather concerns "liberties", that is, rights that each citizen has and that serve to protect his or her interests from the majority. In the United States, for example, these rights included those enshrined in the first ten amendments to our constitution, which are collectively known as the Bill of Rights. The first of these reads: Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances. Exactly what this language...

The question whether video games cause violent behavior is an empirical one. That is, it's one that has to be decided by looking carefully at the evidence, not by reflection on what seems plausible and what doesn't, and anyone who would "dismiss" such a claim "out of hand" is not being very reasonable at all. Nor is someone who bases such an opinion on a vague feeling that "imaginary violence [is] a form of encouragement" being very reasonable. Fortunately, the social scientists who study these sorts of things have other tools. That is not to say, of course, that the tools are sufficient to answer the question, and of course it continues to be controversial whether video games, or other sorts of "media violence", lead to increased violence in practice. It's difficult to account, in practice, for all the variables. That said, I think most researchers would agree that exposure to media violence does tend to make one less sensitive to the real suffering such violence causes and so does tend to make one...

This phenomenon is well-known. It's a form of zeugma that is known as "syllepsis". I think most linguists would say that this sentence cannot mean that Miles has a trumpet and a narwhal a protrusion from the head. The reason is the obvious one: that "horn" has to be interpreted a single way. Note that, if correct, this shows that "Ms and Ns are F" is not , as we sometimes tell our introductory logic students, simply an abbreviation (or something) for "Ms are F and Ns are F", since, in the latter, "F" could be interpreted differently in its two occurrences. When one makes a claim like the one just made, we are talking about how the sentence is immediately, unreflectively, and automatically understood by a hearer. So what I'm observing is, in effect, simply that our "language faculty" operates a certain way, and not another way that it could, in principle, have operated. And put that way, the point should be fairly uncontroversial. The humorous effect one can get from syllepsis depends the fact...

I'm with you. I don't see any reason to suppose that some future person who happened to share your DNA would be you, no matter how similar the course of their life might be to yours. And that's even before we get to the question whether time in infinite (quite possibly not) and whether, if it is, it has the implications that this argument supposes.

All of these are good questions, but we should distinguish two issues. The first issue is as to the moral facts. I claim that if you come to know that use of some term is offensive to the members of some group, then you ought not to use that term. It's an entirely different question, of course, whether someone's telling you does lead you to have such knowledge, or whether your refusing to believe them might be unreasonable, and so forth. Questions about how many people in the group find use of the term offensive are another matter. We might well suppose, for example, that some people of gypsy descent are unaware of the origin of the term "gyp", or that some American Indians might be unaware of the origin of the term "Indian summer". Others might be aware of the origin, but think very few other people are, and so not themselves find use of the term to be offensive. So, well, it's complicated. I haven't thought about this deeply, but I'm inclined to think that the issue here isn't one of numbers,...

I tend to agree with theoretical linguists such as Chomsky that there are really no such things as languages, in the sense in which English and German are supposed to be "public languages". Rather, there are just people who talk, and some of them can understand each other. I mention this because it is surely not an essential feature of any language, in that sense, that it has some particular number of words. Words get added and removed all the time. So it's hard to ask the question in these terms. Let's focus on "idiolects". Each of us has our own idiolect, which is in various ways like and unlike the idiolects of other people. Each of these has, at any given time, a certain number of words in it. Now: Does understanding more words contribute to one's being able to conceptualize and describe more? Other things equal, one would suppose so, and it's hard to see why this ability would, in and of itself, make one's view of things any less clear, though I suppose one might miss the forest for the trees,...

Wikipedia has a decent entry on the Barcan formula. It is generally held to imply that nothing exists contingently, and that in turn is generally thought insane. I would seem to be a good example of something that exists only contingently. But there are some people who think the Barcan formula can be defended, and it would be nice if it could because it makes certain aspects of modal logic much easier than they otherwise are. That said, I am finding it hard to imagine why the Barcan formula and its consequences would be relevant here. If you believe that God exists contingently, then you think the Barcan formula is false. Since not many people accept it, that isn't much of a loss.