I'm told it's arguable that when people say, "Water is H20", what they mean is, "The stuff from around here that we call water has the molecular structure H2O." Well, what about ethical claims? When people say "Killing is wrong", do they really mean "Killing is wrong in all circumstances, times and places"? Or are they saying something more like, "According to the normal values from around here, killing is wrong"?

One might ask why people would hedge the original claim, "Water is H2O," and intend to assert only the presumably weaker claim "The stuff from around here that we call 'water' has the molecular structure H2O." Is it that they don't want to identify water with the molecule H2O but merely want to assert that water is constituted by molecules of H2O? Or is it that they want to hedge against possibilities like Hilary Putnam's Twin Earth, where what the residents call "water" is macroscopically just like H2O but is in fact identical to (or constituted by) a different molecule that Putnam abbreviates "XYZ"? Either of those reasons for hedging the original claim seems to me to be too abstruse to explain the hedging (if any) done by ordinary speakers of the language. But I can't think of a third explanation. So I'm not sure how to compare this case to the assertion "Killing is wrong" or to the hedged version, "According to the normal values around here, killing is wrong." My hunch about ordinary...

If it's possible for a cat to be alive and dead at the same time, or for a particle to be in two places at the same time, would that show there are at least some things about which one couldn't rely on "Either P or not P" as a sound step in reasoning?

Your question concerns the classical law of excluded middle (LEM): For any proposition P, either P or not P. Because logic is absolutely fundamental, ceasing to rely on LEM will have ramifications that are both widespread and deep. In classical logic, we can derive LEM from the law of noncontradiction (LNC), so to give up LEM is to give up LNC or the equally obvious laws that allow us to derive LEM from LNC. We should be very reluctant to do that. In my view, the alleged possibilities that you cite from physics are not enough to overcome that reluctance. First, they are possibilities only according to some, not all, interpretations of quantum mechanics. Second, even if we accept them as possibilities, rejecting LEM or LNC is more costly than (1) reconceiving "being dead" and "being alive" so that they name logically compatible conditions and (2) reconceiving "being here at time t " and "being elsewhere at time t " so that they name logically compatible conditions. It's less costly to mess with the...

It seems to me that most theories involve postulated objects, and then various laws that describe how those objects must or can relate to each other. So, you might postulate an id, ego and superego, or genes, or electrons, protons and protons, etc. It also seems to me that there are at least two types of "simple" when talking about explanations. There's a brevity "simple" -- like a maths proof or a piece of computer coding with minimal steps. And there is also an ontological "simple" -- an explanation relying on as few postulated objects as possible. If it's true that there are at least these two types of "simple", well, does that render parsimony often difficult to apply, if you're committed to it as a good rule of thumb when deciding what to believe in? One candidate theory could be ontologically complex but brevity-simple, whereas the alternative theory might be ontologically simple but convoluted. Here are some things that worry me: (1) does appealing to deities lead to simpler explanations that...

Good questions. The philosopher David Lewis (1941-2001) rightly insisted on distinguishing two kinds of ontological simplicity or parsimony: quantitative and qualitative. Quantitative parsimony concerns the sheer number of postulated entities; qualitative parsimony concerns the number of different kinds of postulated entities. Lewis argued that only qualitative parsimony matters. It's not the sheer number of (say) electrons but the number of different kinds of subatomic particle posited by a theory that makes the theory parsimonious or not, compared to its rivals. (Maintaining this line required Lewis to treat "the actual world" as an indexical phrase and to hold that each of us has flesh-and-blood "counterparts" in nondenumerably many other universes.) All else being equal, then, theories that posit deities are qualitatively less parsimonious than theories that don't, because (I take it) deities are supposed to be of a different kind entirely from the phenomena that they're invoked to explain....

Why is the sorites problem a "paradox"? Isn't it fundamentally a problem of definition?

The sorites problem is a paradox for the reason that any problem is a paradox: it's an argument that leads from apparently true premises to an apparently false conclusion by means of apparently valid inferences. I don't think it's fundamentally a problem of definition, because the concepts that generate sorites paradoxes would be useless to us if they were redefined precisely enough to avoid sorites paradoxes. Take the concept tall man . In order to make that concept immune to the sorites, we'd have to define it in terms that are precise to no more than 1 millimeter of height, because a sorites argument for tall man exists that involves men who differ in height by only 1 millimeter. But defining a tall man as (say) a man at least 1850 millimeters in height would mean that in many cases we couldn't tell whether a man is tall without measuring his height in millimeters. Given the impracticality of taking such precise measurements in the typical case, we'd likely stop classifying men as "tall" and ...

Science claims that the cells in our bodies are alive, but the fundamental parts of the cell such as molecules and atoms are not alive. Does that mean our bodies are only partly alive?

Science also says that some of the cells in our bodies are dead. That already implies that our bodies are only partly alive, but only in the sense that not every part of our bodies is alive. If every part of a living thing must be alive, then the fact that atoms and molecules aren't alive implies that none of our cells are alive, and no bodies are ever alive. Both of those consequences are false. So we must reject the principle that every part of a living thing must be alive.

Recently, I noticed about sorites problem. I thought that problem is serious to all of philosophical endeavor, but my friend told me that is problematic when you assume some kind of platonism. Is he right? Or is it equally problematic when we assume nominalism?

I think that the sorites paradox is a problem even for nominalists. Suppose we line up 101 North American men by height, starting with the shortest man (who's 125 cm tall) and ending with the tallest man (who's 225 cm tall). Let's also suppose that each man except the shortest man is 1 cm taller than the man to his right. Clearly the shortest man is short. If 1 cm in height never makes the difference between a short man in the lineup and one who isn't short, then the tallest man is also short, which is clearly false. So there must be a tallest short man in the lineup. But who could that be? If we can't know who it is, then why not? I think I've managed to state the problem in terms that even a nominalist can accept. If nominalism, as such, evades the problem, then I'd love to know how it does.

Should the impossibility of reaching a definite answer for many of the questions that philosophy asks realistically lead one to stop asking , or even considering, these type of questions? Ultimately, is asking a waste of time and energy?

Philosophers are routinely asked these questions, whereas (say) physicists never are. I'm not sure that's fair. If the task of physics is to discover the fundamental laws governing the physical world, then there's no guarantee that physics can accomplish that task. For one thing, there may not be fundamental physical laws; it may be that for every physical law, there's a more basic physical law that implies it, without end. (The alternatives seem to be that some physical laws are not just physically but metaphysically necessary, which seems implausible, or that some physical facts are inexplicable and therefore not explained by physics.) Even if fundamental physical laws do exist, physicists can't reasonably claim to have discovered them given (for example) the ongoing disputes over how to reconcile general relativity with quantum mechanics. Are physicists therefore wasting their time? Some of the controversies in biology (e.g., abiogenesis; one tree of life or more than one?) seem just as...

Is it possible to employ a truth predicate or truth set (set of all true propositions) in ordinary first order logic?

To my knowledge, no. Ordinary first-order logic quantifies only over individuals (none of which are literally true) rather than over truth-valued things such as sentences or propositions. Thus there's nothing in first-order logic to which the predicate "is true" can apply. For that you need higher-order logic, which is a topic of controversy in its own right. By "set of all true propositions," I take it you mean "a set of all the true propositions there are," i.e., the extension of the predicate "is a true proposition." A Cantorian argument due to Patrick Grim concludes that no such set is possible. It works by reductio . Let T be any set containing all of the true propositions. If T exists, then it has infinitely many members, but that doesn't affect the argument. Now consider the power set of T -- P(T) -- which is the set whose members are all of the subsets of T. It's provable that any set has more subsets than it has members. With respect to each of those subsets in P(T), there is a true...

Mustn't there be a counterexample to any statement that's a generalisation, because if there weren't a counterexample the statement would be a matter of fact and not a generalisation?

It may help to distinguish between universal generalizations and statistical generalizations. An example of a universal generalization is "All swans are white," and a statistical generalization might be "Swans tend to be white." As it happens, that universal generalization is false, because some swans are not white, and the statistical generalization will be true or false depending on the context (in some parts of Australia, it may be a false statistical generalization). When people say things like "That's just a generalization," I take it they're talking about a statistical generalization -- a claim about how things tend to be, a claim about how things are substantially more often than not. The reason that we expect statistical generalizations to have exceptions, I think, is that if the person asserting a statistical generalization were in a position to assert a universal generalization -- a logically stronger claim -- then he or she would. That's why the universal generalization "All triangles have...

I am puzzled about questions that ask if a Creator can create Itself. Look at a circle after it is drawn: at that point, it has no beginning and no end. Look at a circle while it is being drawn: during its construction, you can see it does have a temporary beginning. Only after construction is complete, does its beginning seems to disappear. If time is cyclical, then why couldn't a similar analogy apply? Maybe I'm not expressing myself as clearly as I could, I hope someone here can upgrade the quality of my observation to get at its essence and not be stuck with the poor quality of my language choices.

Speaking of recurrence (!), this topic has come up rather often on this site in recent months. My own answers appear at Question 25260 and Question 25648 . In reply to Question 25260, I conceded that we can tell a story featuring a causal loop in which -- allegedly -- X creates Y in 1900, with Y already having created X in 1800. However, because Y already existed (indeed, Y created something) in 1800, I can't see how X can create Y in 1900: I can't see how X can create something that already existed (indeed, something that existed even before X did). Instead, I'm inclined to describe the story as one in which X and Y come into existence for no reason at all, and not because either of them creates the other. As I interpret it, your analogy to drawing a circle is meant to suggest that the story might have an actual, unique starting point that we can no longer identify because the story has now come "full circle": the drawn circle is now closed. But that suggestion, I think, misunderstands the...

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