Mike, Thank you so much for the response! I LOVE your book so far. I am on lesson 17 currently.
I am really struggling with necessary/sufficient. For example on PG 246 you wrote the abstract language drill. I really struggled with it but most of all I struggled with the answers that mentioned "x is sufficient for a result that the absence of that factor is sufficient for the opposite result" or " fails to address adequately the possibilities that even is a condition is sufficient to produce an effect it may not be necessary"
I read back over lesson 6 and 7 in the necessary/sufficient blurbs, but I am still having a really hard time understand the difference between confusing necessary with sufficient and sufficient with necessary. It makes my brain hurt! Please help.
I am also struggling with finding the flaw, any advice on solidifying the different types of flaws? (apples/oranges etc)
Hey -- it makes my brain hurt too -- hope this helps clear things up a bit --
First, let’s lay out a basic definition of the terms necessary and sufficient.
is something that needs to be. We need to drink water to live. It doesn’t guarantee that we can stay alive, but it is something we need to do. In a similar way, a necessary premise is one that absolutely needs to be correct in order for an argument to work (but won’t guarantee that an argument will work), and a necessary consequence is a result that absolutely needs to (or must) happen if a certain trigger is satisfied.
is something that is enough. So, a sufficient premise is one that is enough to guarantee the validity of a certain conclusion.
So, let’s imagine you want to buy a certain poster for $30.
You look in your wallet and you have $50.
Notice, the amount of money in your wallet is enough, or sufficient, to buy the poster.
Do you need to have $50 in order to buy the poster? No -- you need to have at least $30. So, having $50 is not necessary for achieving the result (buying the poster).
To think of the situation a slightly different way --
Do you need to have more than $5 in order to buy the poster?
Yes, absolutely -- if you don’t have more than $5 you won’t be able to pay for it.
Does having more than $5 guarantee that you can get the poster?
No -- it doesn’t guarantee you have enough to buy the poster. You need at least $30 -- maybe you just have $6.
So with all that said, let’s look more carefully at the two phrases you mentioned:
“X is sufficient for a result that the absence of that factor is sufficient for the opposite result.”
In simpler language, what this means is that the author made the following mistake:
He/she assumed that since knowing A was enough to prove B, knowing the opposite of A must be enough to prove the opposite of B.
Using our example of the $ and the poster, -- a reasoning mistake that would match this would be “Since having $50 guarantees that I can buy the poster, not having exactly $50 must guarantee that I can’t buy the poster.”
Notice, per what we discussed above, that it would be a mistake to infer such a thing -- for example, you could just have $40 and still buy the poster.
The second phrase you mentioned was “fails to address adequately the possibilities that even if a condition is sufficient to produce an effect it may not be necessary.”
In simpler language, what is means is that the author is made the following mistake:
He/she forgot to think about the fact that even though something might be enough to guarantee a conclusion, it may not be needed for guaranteeing the conclusion.
Using the poster example, a reasoning mistake that would match this would be, “Since having $50 guarantees that one can buy a $30 poster, it is necessary for one to have $50 in order to buy the $30 poster.”
Again, notice that having $50 is sufficient, or enough, for buying the poster, but it’s not something that needs to be, or is necessary.
Finally, in terms of flaws, unfortunately I don’t have any magic advice about that -- being good at identifying flaws is not a black and white situation, but rather something you want to get better and better at throughout your studies --
Here are a couple tips you might find helpful --
1) When you experience symptoms, look upstream for the causes
Typically, when we run into problems on the LSAT, the causes of those problems happened well before -- for example, if you get stuck between two answer choices, it’s far less likely that it has to do with those particular answer choices, but rather with the way you thought of the problem up to the point when you started evaluating those answer choices --
When it comes to identifying flaws, there are several essential steps you have to perform well in order to put yourself in the right position -- namely --
1) you have to correctly understand the point/conclusion
2) you have to correctly emphasize with the author and correctly isolate the reasoning he/she is using to justify that point
3) you need to put yourself in a mindset where you focus in on just that conclusion and the support and make it your goal to understand, as best you can, why the support given doesn’t guarantee the conclusion reached.
So, when you have trouble IDing a flaw correctly, I suggest you always start your review with a focus on the above issues -- per my experiences with other students, I think it’s highly likely that getting sharper and sharper at those 3 steps will be the most important factor in terms of you getting better and better at recognizing flaws correctly.
2) Learn from your challenges
This falls into the “duh” category of advice, but as I mention often, your misses are your blueprint to a better score -- so, every single time you miss a flaw problem, or find one overly challenging, make sure to study it intensely and to not let it go until you understand completely, for yourself, in your own words, what the author’s point is, what the reasoning is, and why the reasoning doesn’t guarantee a conclusion.
You can use my flaw categories and such as a means to an end -- as a way of trying to understand flaws better -- but categorizing is not the same thing as understanding, and again, at the end of the day, your bigger goal is to try to understand each and every flaw you run into as best you can (and if there are any LSAT arguments you struggle with and after the fact just can’t see the flaw for, let me know and I’ll try to help as best I can) -- and, in addition to trying to understand them, with each new tough flaw you run into, do your best to organize/compare/relate it to other flaws you’ve seen, and you are likely to find the same types of arguments challenging you again and again (and the moment you see that (and why) clearly they will stop challenging you so much) --
I hope that helps --
One last thing I want to mention is that I’ve recently gotten a couple of related q’s on Lsatters -- I’ve answered one q and will be posting a response to the other as soon as I have some time -- figured you might be interested and find these discussions helpful --
http://lsatters.com/forums/topic/suffic ... necessary/
http://lsatters.com/forums/topic/words- ... uarantees/
Glad to hear you are finding the book useful and let me know if you need anything else -- Mike