I've been wrestling with this problem for some time. My question concerns the concept of 'possibility'. When one says that something is possible, they are saying that something might be but may not be as well. There is an uncertainty. And of course whatever it is cannot both be and not be at the same time. Now, when we say that something is 'not possible', we are saying that something is not and cannot be. There is no uncertainty and the term as used does not seem to be a true negation as is usually meant when the term 'not' is used. What confuses me, is that in when actually trying to negate the concept of possibility, such as when saying 'not possible', aren't we on the one hand saying that 'that which might be' is not, and on the other hand that 'that which may not be' is not as well, and therefore is (or could be)? What may be is not and/or what may not be is. Saying that something is not possible, in this sense, is the same as saying that it is possible, thus making the negation of the concept...

I don't think there's a deep puzzle here, as I hope I can explain. The kind of possibility that stems from uncertainty is usually called "epistemic possibility," often signaled in English by "may" or "might," as in "There may [or might] be life on other planets." We're far from certain that there isn't life on other planets, so there may [for all we know] be life on other planets: life on other planets is an epistemic possibility for us. There are other kinds of possibility, such as metaphysical possibility, but I think the general point I'll make applies to all of them. To deny possibility in this sense, to say that some state of affairs S isn't epistemically possible for someone, is roughly to say that he/she is certain that S doesn't obtain, or at least he/she knows that S doesn't obtain (if knowledge doesn't require certainty). So I'd say that, right now, my own non-existence is epistemically impossible for me, because I know (indeed, I'm certain) that I exist, for the reason Descartes gives...

The general consensus seems to be that since men aren't women, they can't speak about or fully understand the issues pertaining to women. I once read an analogy that tried to equate this logic with someone telling a veterinarian that since he isn't a cat, he cannot speak about the issues pertaining to cats. But since veterinarians do speak about cat issues, then it is safe to assume that men can speak about women's issues as well. Does the analogy work? Can men speak about women's issues?

To start with the literal truth: Men can indeed speak about issues pertaining to women, because (some) men do speak about such issues, which proves that they can . The question is how authoritative, how credible, about those issues a man can be. I think that will depend on the issue. An appropriately trained male researcher can speak with authority about (for example) the long-term health effects of this or that means of female contraception. But if the issue is more "experiential" or "phenomenological" -- such as "What does it feel like to be a female victim of workplace sexual harassment?" -- then it seems clear that any male has at least a burden of proof to discharge before we should regard his statements as authoritative or credible. I'm not saying that this burden can't possibly be discharged, only that it exists. (Clearly, I assume that speaking credibly about whether a man can be authoritative on issue X doesn't require me to be an authority on issue X itself.) For my answer to a...

Could I have come into existence and experienced my "self" if my ancestors had not been the same persons, or if a different sperm cell had coupled with my mothers egg? Would my "I" then have remained unborn or been born to a different body, maybe at a different time, or my vacancy occupied by a different persons "I"? In order for a particular "I" to be realized, must it have existed as a potential beforehand, like a lottery tickets potential for winning? Evolution and probability theory indicate that the chances for any particular individual to exist is practically zero. Have we who exist been incredibly lucky, or can our "I" be realized in some other being? If so, on what grounds is the particular potential self assigned to a particular body. I have explored several philosophical texts hoping to find something about this topic, but without success. I would be very glad if you could comment on it or direct me to some illuminating textbook or other source.

Your questions touch on several interesting and difficult issues. If you haven't already consulted it, I recommend looking at the SEP entry on "Possible Objects" . It's a somewhat challenging read, but it contains discussion (for example, in Section 2.2) of the issues you raised, and (as usual for the SEP) copious references that you can follow up. Best of luck as you grapple with this topic!

Premise 1: If God does not exist, objective moral values and duties do not exist. Premise 2: Objective moral values and duties do exist. Conclusion: Therefore, God exists. Can we accept the conclusion above as valid or even fact?

The argument itself is logically valid -- indeed, formally valid. It uses only modus tollens and the rule that "P" and "~ ~ P" are equivalent, both of which are valid rules of inference. However, I think the argument is unsound -- and therefore I think it fails to establish its conclusion -- because Premise 1 is false, at least if Premise 1 is meant as a strict conditional. (I think it's also false if it's meant as a material conditional, but that's more controversial.) For excellent discussion of Premise 1, I recommend this article and this collection of essays .

My question is on death. I am young and have read a lot. A few people have passed in my short lived life and death is an interesting topic for me. Many people believe death is not the end, they say it is the beginning of life. How can it be the beginning if you are dead? Your body is dead I believe, but the soul lives forever even if it rotts in hell. Many claim they are not afraid of death. I think its true death is nothing to be afraid of. What we are afraid of is letting go of our bodies, of life as we know it. I am 12 and do not quite know my own theory on death, but I believe death is a great mystery and I like to study the different answers and everything. My question is - Is death real and should we be afraid?

It's wonderful to hear that at the age of 12 you've already read a lot, and I'm impressed by your submission. Many people twice your age wouldn't be able to submit something so thoughtful. I would recommend that you take a look at the essays in John Martin Fischer's edited volume on the metaphysics of death . I found it helpful when I read it many years ago; it contains both tough-minded philosophy and also bits of comic relief. You may find it a challenging read, but I don't think it's beyond you. Nowadays there may be more up-to-date collections on the topic, but Fischer's volume is an excellent place to start.

Can we unknow what we already know?

I'd say yes . One way would be if (for whatever reason) you ceased to believe some proposition P that you formerly knew to be true. If belief is a precondition for knowledge, then you'd no longer know that P. Another way might be, while retaining your belief of P, to come to believe (or indeed even know) some proposition Q your belief of which undermines your justification for believing P and thereby deprives you of the knowledge of P that you formerly had. See Carl Ginet's article "Knowing Less By Knowing More" (linked here ).

I think of philosophers as people who describe and debate in order to reach defensible positions concerning ethics, truth, etc. But what is uniquely philosophical about such practices? Philosophers identify fallacies, but so do logicians. Philosophers are trained in intellectual movements, but so are historians. As Rorty put it, where is the fach in philosophy? Is philosophy more about excellence in argumentation than content?

I myself would answer "Yes" to your final question. I think you've put your finger on what distinguishes good philosophers from good practitioners of other disciplines: the desire and the ability to attain the highest standards of argumentative attentiveness and rigor regardless of the topic at hand. We can rely on good mathematicians, physicists, and biologists (for example) to be careful and rigorous about math, physics, and biology. But get them outside their scientific specialties, and the results are very much hit-or-miss, with a lot of miss: Richard Feynman, Stephen Hawking, Neil deGrasse Tyson, Lawrence Krauss, Jerry Coyne, and Bill Nye on the nature and value of philosophy; Sam Harris on free will and on the ability of science to resolve ethical questions; Coyne on free will; Richard Dawkins on free will and on the sorites paradox; Krauss on why there's something rather than nothing. Those are examples of sloppy argumentation that come readily to mind from just my own reading. It's not...

My dictionary's definition of "definition" is an "exact description of a thing". The definition doesn't contain an exact description of a thing, it only mentions it, so it doesn't qualify as a definition. Paradox?

I'm intrigued by your suggestion that there may be a paradox here, but I'm having trouble reconstructing your reasoning. As far as I can tell, your reasoning relies on the premise that any definition must contain whatever it defines . But I'm not sure that premise is plausible. Merriam-Webster.com defines "walrus" as follows: "a large gregarious marine mammal ( Odobenus rosmarus of the family Odobenidae) of arctic waters that is related to the seals and has long ivory tusks, a tough wrinkled hide, and stiff whiskers and that feeds mainly on bivalve mollusks." That definition (more precisely, the definiens ) doesn't contain the word ("walrus") being defined, which is good: otherwise the definition would be unhelpful. Nor does the definition contain a walrus; we'd need a cage to do that. Instead, the definition gives us a string of words meant to pick out the walrus from among other things. If it's a genuine definition, then the principle on which it seems you're relying is false. But I may...

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 really mean just "technologically 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 regarded as 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 .

I had a brief chat with a work colleague today about the nature of reality and our perception of it. Essentially, his contention was that because we all basically agree on our external physical reality (e.g. when I hand him a cup of tea we both agree that I've just passed him a cup of hot tea), there must be an external reality because we both seem to agree on what it's like. If there wasn't such an external reality and we didn't essentially agree on it, he pointed out, we wouldn't be able to even ask for a cup of tea because my idea of what a cup of tea actually is would be totally different (or at least different enough to make meaningful communication difficult). Therefore, he concluded, it's common sense that we must be talking about and looking at the same "real" things and that we both experience them in the same -- or very similar -- way. Age-old philosophical problem solved! But it can't be that simple. So my question is what are the main problems with this "consensus" view of reality? Or, to put...

I've seen only one of the Matrix films, the first one. You might ask your colleague how he can be certain that things in our world aren't as they're portrayed in that film: that is, you and he merely believe you're conversing in the ordinary way about an ordinary teacup, when in fact you're both hooked up to a computer that's simulating the conversation, the teacup, and your surroundings. Is there some internal indication, something about the way things feel to him during such a conversation, that rules out a Matrix-style simulation? What could that be? Granted, neither you nor your colleague are at all inclined to believe that you're living a simulated existence, but that's just how the Matrix wants it!

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