@"Rigid Designator" said:
A year ago I would've taken on the challenge to defend my boy, Kripke. But having just spent 20,000 words arguing that A Puzzle about Belief is not really a puzzle, I'm less inclined to die on the hill of Kripke-fandom, ha…
@Q.E.D said:
Do you follow the literature on symbolic logic, @quinnxzhang?
I focus more on philosophy of language, but I've TA'd both first-order logic and mathematical logic courses. The logic literature I read tends to bend towards the philosophi…
There's a lot of confusion in this thread. The contrapositive of 'P -> (~M -> ' is straightforwardly '~(~M -> -> ~P'. With one application of De Morgan's, this is equivalent to '(~M & ~B) -> ~P', as @Q.E.D said. I don't see the p…
@"Jonathan Wang" said:
logic is just a branch of mathematics
Oh man, don't tell the mathematicians this.
There's a somewhat famous story about Paul Cohen (mathematician) looking down on logicians and trivializing their work. In response, some log…
@Euthyphro said:
(~V S) & (V ~S)
This is redundant. The two biconditionals in your conjunct are equivalent.
@Euthyphro said:
So is this a different way of showing the same relationship, if so do you prefer one method over the other? …
@generationhar said:
If you are Bob, then you are tall.
If you are not tall, then you are not Bob.
This is not what "Bob is tall" is saying. Your conditional sentence can't even be expressed in quantifier-free predicate logics, whereas "Bob is t…
@generationhar said:
Can't all statements be translated into conditional statements?
Certainly not. Consider an atomic proposition like "Bob is tall". Where is the conditional here?
Contrapositives only apply to conditional statements. An existential statement like "some criminals are politicians" has no conditional, and thus no contrapositive.
@generationhar said:
C P
I recommend changing the way you diagram existential sta…
I think this is all too convoluted. Much simpler to just understand that, classically, "A→B" is equivalent to "~A or B".
So for "~A→B", this is equivalent to "~~A or B", which is in turn classically equivalent to "A or B". This means at least one o…
Sufficient and necessary conditions are features of conditional statements ("if P, then Q"), whereas premises and conclusions are features of arguments ("P. Therefore, Q").
In classical logics, there's something called the deduction theorem (https:…
I think redoing games loses its effectiveness past a certain point (for me, this is around 3 times) for exactly the reason you cite. There's really nothing that beats doing fresh games. If you're almost out, you can look for unofficial games via som…
There are two ways to approach these questions.
The first way is to go through each answer choice and see if the answer choice conforms to every rule. Using this method, you do have to go through every rule for each answer choice until you find a r…
If there were a way to figure it out, there would be no point in having an experimental section.
That said, statistically speaking, the scored sections usually add up to 101 questions. This isn't a great indicator, though, because often there are f…
Something to keep in mind is that the February test is undisclosed. So if February is going to be your second take, you won't know which questions you missed and whatnot. This might matter if you end up waiting an application cycle for a third take.…
What these terms mean depend on the context.
In formal logic, "contradiction" has a very precise meaning to describe when both P and ~P are the case. This means that you can have inconsistent sets where none of the wffs are contradictions of each o…
@civnetn said:
So I understand what you're saying, but just because the author doesn't explicitly state there is an implicit premise in C) doesn't mean there isn't! It could very well be the case that a delay in presentation isn't possible.
This …
What makes (D) better than (C) isn't the strength of the conclusion. What makes (D) better than (C) is that (C) is just not an instance of the same argument form.
The argument in the stimulus relies on modus tollens (P→Q, ~Q, therefore ~P) with one…
@"Cant Get Right" "Except" is not always a biconditional.
Consider: No apples except red ones are edible. This expresses something like "apple & edible → red". However this does *not* mean "red → apple & edible". After all, firetrucks are a…
@Euthyphro said:
I have noticed while going through the SA and PSA questions that the answer choice must have the conclusion in the necessary condition.
This isn't true. I semi-randomly looked at three recent SA questions -- 77.4.24, 77.4.20, and…
This can be a pretty thorny philosophical question, but for the purposes of LSAT RC, I think it's helpful to think about the different attitudes an author might have towards a hypothesis vs. a thesis.
Someone's hypothesis is something like a workin…
You need to use context to disambiguate the scope of the negation. For this question, the second sentence clarifies the scope by saying "Once sterilized and properly sealed, **HOWEVER**, it contains no bacteria." The "however" links together the fir…
@"Cant Get Right" said:
That’s really interesting. Totally makes sense. @quinnxzhang , you aware of any LSAT questions hinging on this distinction?
I'm sure there have been generic sentences in, say, some of the RC passages, but I'…
@"Keane Xavier" said:
For these reasons, I cannot infer from the generic statement "small animals move more rapidly than large animals" that all small animals share that ability. The quantity of small animals that move more rapidly than large anima…
@"Keane Xavier" said:
Because the author is talking about these animals as sets - small animals and large animals - can we infer that he or she is talking about all small animals and all large animals? Can we thus read this statement as, "All small…
@westcoastbestcoast said:
I thought that the sentence that contains the condition in which the company allows Ann to leave was a bi-conditional and therefore we could get the contrapositive of the bi-conditional by negating both terms. …
I used that watch. It worked fine, but the dial is a bit difficult to turn, so you may want to grow out your nails a bit for the test. Looking back, though, I personally think it was a waste of money, and I would have been fine using any regular ana…
@Euthyphro said:
So for example All J are F = (J --> F) and to negate we take the contrapositive (/F --> /J)
The negation of 'J → F' is not '/F → /J'. The contrapositive is logically equivalent to the conditional, so it can't be the conditi…
What's at stake here isn't the difference between disproving and contradiction. Rather, what's at stake here is the difference between being contradicted by someone else and contradicting oneself. You can make a decent case that the opponent's claim…