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17

Recall that in formal logic, your expressions are used as follows: A if B means that B implies A. A only if B means that A implies B A if and only if B means that A is equivalent to B. For example if in the morning I tell my wife "I'll buy that shirt we saw yesterday only if it costs less than 40 dollars" and she sees me wear it in the evening, she can ...


16

"Either A or B" most precisely means, in symbolic logic terms, "A XOR B", where XOR is the "exclusive or". So yes, it means "A or B but not both". It isn't always actually used with full precision, though, so, as usual, context has to be taken into account. If somebody says, "select either A or B", for example, they definitely mean that you should not ...


16

This is bordering on logic rather than language, but the answer is definitely no: Some is "an indeterminate amount", which means it can be all. If I say I have some red M&Ms in my bag, it could be that all of them are red. But then, depending on inflection, as @codelegant pointed out, I could be using emphasis on some to indicate that not all are ...


15

This is the Cooperative Principle in action: (link to comic) If you have no particular reason to think I will buy you a wallet and I say: I will buy you a new wallet if you need one. then, under the Cooperative Principle, you can safely assume that this is all you want / need to know. But if there were other conditions in which I'd buy you a wallet, ...


15

The original was actually Shakespeare: all that glisters is not gold, but that needn't concern us here. OP has simply misparsed the sentence - it actually means "Not everything that is gold glitters" (which is to say, "There are some things which are gold that don't glitter"). You can always Google "every x is not y" for more discussion of why this type of ...


15

Languages are not formal logic systems, and words do not derive their meanings from the definitions in dictionaries. If they did, then your argument would mean something, but as it is what you have is an amusing but pointless exercise. Words derive their meanings from their shared usage in a linguistic community, and those meanings are ultimately grounded ...


14

You're correct, it is indeed contradictory. Taken purely logically, then if neither can live while the other survives, then if Harry is alive Voldemort must be dead and if Voldemort is alive Harry must be dead. Since we know both Harry and Voldemort are alive, the statement is clearly false. Since the statement is part of a piece that refers to them as ...


12

No; the sentence "Is it true that 1 + 1 = 2?" is perfectly grammatically correct. In logic, there are tests that depend on being able to prefix almost arbitrary sentences with "It is the case that ..." or "It is true that ..." and if the result still makes sense, then certain properties hold (it is a declarative sentence which could be a proposition). For ...


11

Fairly obviously there can be multiple X's, any or all of which may be 'arguably' the best X. To qualify for that designation they only have to be capable of being argued for – they don't need to actually be the best. Equally obviously there may be some X's which are so bad they're not remotely capable of being considered for 'best', and some other X's that ...


11

Shakespeare's line is the best known example of this general phenomenon where a universal quantifier scoping over negation gives a counterintuitive meaning. The expected meaning of: All that glisters is not gold. Would be: For each thing that glisters, it is not gold. Instead, the meaning to be understood is: Not everything that glisters is ...


10

Quoting the Wiktionary usage notes for center: Merriam-Webster's Collegiate Dictionary observes that center around is objected to by some people on the grounds that it is illogical, but states that it is an idiom, and thus that such objections are irrelevant. It offers revolve around as an alternative to center around for those who would avoid the idiom. ...


10

You're correct: subsequently doesn't imply causation. subsequent: Following in order or succession; coming or placed after, esp. immediately after. consequent: Following as an effect or result; resulting. (Both definitions are from the Oxford English Dictionary.) You might use subsequently to avoid the post hoc, ergo propter hoc fallacy.


8

To get the logical negation of "must", switch must with a different verb. A: We must study English grammar. B: No, we need not study English grammar. or B: No, we don't need to study English grammar. or B: No, we don't have to study English grammar. or B: No, we are not required to study English grammar.


7

"Consequently" contains information about causality and "subsequently" does not, but that doesn't mean "subsequently" is improper. Did B (humanity lost its resistance to the common cold) happen after A (the common cold died out)? Yes? Then of course B happened subsequently to A. While "consequently" means that A caused B, the presence of "subsequently" ...


7

No, therefore should not be reserved for conclusions beyond a reasonable doubt. It is merely a transition similar to thus or as such: Therefore, I ordered pepperoni. Thus, I ordered pepperoni. As such, I ordered pepperoni. The extended conversation could have been: I like meat on my pizza. Therefore, I ordered pepperoni. You can test ...


7

The biggest problem in finding a technical fallacy is that "absurd", in this context, isn't detailed enough. Why is it absurd? The idea that any absurd thing could be believed if it was simply absurd enough is not really true. The idea of arguing something as true because no one would make it up is close to these fallacies: appeal to authority — ...


7

It means not everything that is gold glitters. Tolkien undoubtedly was borrowing from Shakespeare here, specifically the poem that one of Portia's suitors discovers when he reads the scroll associated with the golden chest that he has (to his loss) chosen: “All that glisters is not gold— Often have you heard that told. Many a man his life hath sold ...


7

You are correct; Karan of the superuser question you referenced made a grammatical error. It should have been as you phrased it: Not everything in DOS is plain-text That being said, your understanding in the two examples you posted is slightly off. It should be Every human is not a man. There is no human being who is a man. Not every human is ...


7

A circular argument is one where the conclusion is also one of the premises: Good websites are the ones that are effectively designed. In other words, in premise / conclusion form: If a website is effectively designed, then it is good. This is essentially defining good to be equivalent of effective, therefore the conclusion is the premise. ...


6

In propositional calculus especially, there is a very small number of symbols available, and a very small number of ways they can combine. So it's tempting to thing of this small stock of mostly special characters ( ¬ ⋀ ⋁ ⊃ ≡ p q r s ) as an alphabet. In fact, however, these letters don't represent parts of words -- rather, they are words, and represent ...


6

Your co-worker is misinterpreting the statement. The "error" is in the interpretation of the word error Error can mean: a mistake or inaccuracy but it can also mean the condition of deviating from accuracy or correctness The first is countable the second is not. I believe the intention is to say, that amendments are only allowed in 2 ...


6

The sentence is ambiguous, and could mean either of your two choices. English is not math, and trying to write a sentence that conforms to the rules of mathematics or formal logic can often diminish clarity instead of enhancing it. Instead, it is better to write the sentence in whatever way will get your point across clearly, with a minimum of ambiguity. ...


6

<statement type="highly opinionated"> I don't think any human language is well-suited to "natural language programming". I don't think there is any such thing in real life. Computer people are always saying, "Wouldn't it be great if instead of having to learn all these complex commands, you could just tell the computer what you want in ordinary ...


5

The main problem in both cases is this: how to convert real language into logical language. In order to do this, one must choose how to interpret real language. This is often difficult, because real language deals with information that is often not apparent, such as implicit premises and the wider context. X1: I paid $10 for that hamburger. Y1: ...


5

The key issue is the ordering of auxiliaries in English. (Subject) + Modal + PerfectMarker + ProgressiveMarker + PassiveMarker + (MainVerb) + (...) An example of all the auxiliary positions being used is: We must have been being taught English grammar. Negatives occur after the element they are most relevant to (often the first). Since must is a ...


5

This dates back to the Coldstream Guards The regiment is ranked second in the order of precedence, behind the Grenadier Guards. This is because the Grenadier Guards have served the Crown for a longer period of time. However, the Coldstream Guards is an older regiment, and because of this, has the motto Nulli Secundus (Second to None). The regiment has ...


5

Firstly, written expressions suffer from lack of the intonational advantage of speech. Furthermore, there are such ambiguities galore in the English language, probably far more than in most of the other 'conservative' languages, i.e., those that well-defined and relatively static. In writing, I might use an expression like: "I'll buy you a new ...


5

There are too many ambiguities in English as a whole to make it useful as an NPL. Even in languages that use pieces of English, prepositions like in and from can point to the same idea but yield drastically different results when the implied meaning "looks right" to the human eye but causes the interpreter or compiler to go in the (from a human viewpoint) ...


4

Yes, you are right. 'Therefore' is used to link a statement which logically follows another one. It cannot be used in a standalone statement. I would not say therefore should be used when something is being concluded beyond reasonable doubt. It can be used to connect two statements that 1) the user believes is logically correct 2) the user ...



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