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Messages - noumena
« on: June 07, 2009, 03:10:56 AM »
It's hard to communicate accurately over the web, and I apologize for dragging you along with me in my imperfect quest.
But it seems like I've finally demonstrated what I have been trying to say all along.
The disturbing thing about this is this isn't
the only question of this type in which the above error is committed. There are literally examples strewn front to back that seem to fall trap to this error. I spent the afternoon today just trying to figure out why such errors keep recurring in their book. If you have the newer edition (I have the webcom edition, as I stated), do you recall encountering such problems?
Thanks much (again),
« on: June 07, 2009, 02:53:08 AM »
6 Slots. Y before X and Z. (More than one element possible per slot.)
We can deduce that neither X nor Z can go into slot 1, as above.
We still don't know anything about slot 2. No matter how many elements can go there, Y or X or Z or (X and Z) could go there.
We can deduce that Y can not go into slot 6. Here, we don't know about slot 5 though. Y could go there, with X and Z in slot 6.
I am not having trouble recognizing the logic behind slots 1 and 2. I know why X and Z are eliminated from slot 1, but not 2. What I am having trouble understanding is why one should put ~Y underneath slot 5. As you yourself said int he quote above, Y COULD go into slot 5, provided X and Z both go into 6 together, since as the rule states, Y occurs before both X and Z.
Here's the picture of Powerscore's answer:
Putting a ~Y that early just right off the bat removes your scenario D from consideration, when maybe if more clues later were given, Y might turn out to in fact be in in slot 5 (Scenario D). How can such a diagram be correct if it eliminates a possible scenario without further evidence?
« on: June 07, 2009, 12:11:15 AM »
Thanks again, but my last post was on a different example. There are NO conditions or instructions other than to diagram the fact that Y is examined before X and Z are examined. It tells us only that there are 6 total examinations, and, like you said, no information as to whether perhaps 1 might occur on separate occasions.
I'm not sure whether those 4 scenarios that you typed up pertain to my last post, or my original post. The variables you chose and language are mixed up.
At any rate, I'm about to send you the pages that I'm talking about. You'll see what I mean then.
IMAGES HERE: http://picasaweb.google.com/changesmyweltanschauung/Powerscore#5344435170144698690
« on: June 06, 2009, 07:56:51 PM »
Not to belabor this...but here's a paraphrase of one of their drill questions:
Diagram the following statement: Y is examined before X and Z are examined. There are 6 examinations:
What the hell?! Now they've flipped. They DO recognize that X and Z could occur together in the second slot, and so just eliminate the possibility of them occurring first, but now Y for some reason cannot occur 2nd last. But that presumes X and Z cannot occur simultaneously in the last slot!
That's it...I'm throwing away this book.
« on: June 06, 2009, 07:35:26 PM »
Wow that stinks!
Thanks for the notice.
« on: June 06, 2009, 07:02:38 PM »
Thanks for your response. What I meant was, IF Powerscore had been consistent in their implementation of whatever erroneous logic they were using (which it seems you agree with me about in the case of the ~R), then they would have applied that same consideration in slot 5. After all, their point in putting ~R in the second slot seems to be to imply that not putting it there would require for either P or Q to be "bumped" out if R were in the second slot (keeping in mind that it's stated that BOTH P and Q have to occur before R) IF they in fact occurred separately. That is, they presumptively and unwarrantably eliminate the possibility of P and Q's happening simultaneously in slots 1 and 2, but recognize the legitimacy of that scenario obtaining with regard to slots 5 and 6.
I hope I am making myself clear. I just want to survey what you guys' intuitions are about this. It seems like a horrible typo to me, but I've been studying their book, and the same sort of logic is applied uniformly throughout in their examples (with nary an explanation). In ANY case involving similar conditions (i.e.,only the fact that some variables occur before or after another variable is known; we don't know if they might occur separately or simultaneously), they eliminate the possibility of those variables occurring simultaneously at the beginning of the base sequence, but don't do so (this being the correct modus operandi) for the end of the sequence. I have a feeling that IF this isn't a typo, and we're just both wrong (how can we be? P and Q COULD both occur together), then there must be some sort of logical rule or shortcut that they are applying that we just don't know.
p.s. if someone would be so kind and volunteer to help me out, just so I don't go crazy (I can't study past this page if I am not certain the book isn't crock), please PM me--I'll send you a scan of the relevant pages for you to examine.
« on: June 06, 2009, 06:50:03 PM »
I think "A if, but only, if B" says something different from "A if and only if B." All "if and only if" statements can be parsed into a conjunction of two stipulations: (keeping your variables) A if B and
A only if B (i.e., A as necessary and sufficient conditions, respectively).
It is true that in most semantic contexts, "but" serves to emphasize an otherwise uninteresting conjunction (I studied little and I passed vs. I studied little *but* I passed); in this case, however, the "but," set off in a restrictive relative clause, constrains the meaning. I think in effect, the "but only if" part of the statement "swallows" up and replaces the "if" part of the statement. It is as if the speaker corrected himself mid-sentence.
For instance, if your annoying cousin nagged you about taking him to swim, you might say "okay, if you finish your homework." If you said that, you would be promising to take him to swim once he finished his homework. But you could be sneaky and say "Only if you finish your homework," in which case no promise would have been uttered. I think "A if, but only, if B" approximates this sense more than the former (just repeat the following statements--they do sound like they mean different things: okay, if you finish your homework
VS. okay, if, BUT only if, you finish your homework
. Otherwise, it's just redundant (why would you say, in normal linguistic contexts, that something is both a necessary and sufficient condition if it is going to be sufficient either way?--it serves only to confuse your poor cousin!).
Having said this, I am not certain, however, if I am right (or if there is a right answer). A if, but only, if B, is not a conventional usage. It's ambiguous, because I have a feeling (going by previous posts) that our intuitions do diverge here. It shouldn't be on the LSAT, IMO. They should stick with the traditional IFF (if and only if) construction. I think we will just have to accept whatever opinion LSAC has about this.
So does anyone who recently took the test know which side they're on?
« on: June 06, 2009, 06:04:07 PM »
There is a "strategy" in Powerscore's Logic games bible that I'm not sure is really sound; it concerns the diagramming of uncertain relationships.
For instance, it says that if you are told only that 2 items, say P and Q, must occur before another, let's say R, in a 6 day week, then you would diagram something like the following:
....-.........- - - - -
~R ~R (~P,~Q)
(periods inserted to simulate the diagram as it would appear in your own notes...just imagine they aren't there)
I have doubts as to whether it is wise to so quickly eliminate R from possibly occurring second in the sequence. First of all, the Logic games Bible states that since we are not told what the relationship between P and Q are, we only know that it may be that P occurs before Q, Q occurs before P, or they occur concurrently. But if we can't rule out that last possibility of P and Q occurring at the same time, then how can we presumptively cross out R underneath the second slot? That presumes that P and Q cannot occur at the same time, and so that R cannot occur second in the sequence.
Furthermore, the logic in their notation for these first two slots and the last slot seems inconsistent. In the last slot, the possibility of P and Q's occurring simultaneously is taken account of--the 5th slot doesn't eliminate P and Q from possibly happening together, and so notes correctly that R might occur last. Otherwise the author would have indicated that because P and Q might occur separately, if R occurs right after either P or Q, then there is a chance that because one of the disjuncts (i.e., P, Q) might "bump" R out of the last slot, then ~P and ~Q should likewise be indicated below the 5th slot.
If anyone can shed some light on this, I'd be really grateful.
p.s. following the tradition of philosophical logic, I have represented all 'nots' in my "diagram" with the tilde (~) symbol.
p.p.s. if you want to follow along in your copy of the Bible, I have the Webcom edition, and it's on pgs 17-18. Or you can view scans of these problems here: http://picasaweb.google.com/changesmyweltanschauung/Powerscore#5344435170144698690
« on: March 11, 2009, 11:58:10 PM »
Many thanks to all of you; it's people like you who make this place really flourish. I submitted my $65 payment today and look forward to the ceremony!
Hey, one more line on the resume never hurt anybody!