Law School Discussion

How can a sufficient and necessary condition occur at the same time??

Well......how do they?? Any examples would be helpful!

PNym

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Re: How can a sufficient and necessary condition occur at the same time??
« Reply #1 on: August 17, 2007, 09:04:12 PM »
Well......how do they?? Any examples would be helpful!

If you agree to testify against the Don, the DA will immediately drop all charges.

Re: How can a sufficient and necessary condition occur at the same time??
« Reply #2 on: August 17, 2007, 09:13:23 PM »
ahhhh I think I get it!! Any more would be very beneficial!!

Re: How can a sufficient and necessary condition occur at the same time??
« Reply #3 on: August 17, 2007, 09:21:41 PM »
Sorry for the lack of content. I just did not make the connection that both conditions can occur simultaneously. I thought one had to occur for the other to occur but I did understand that either can come first. So, basically a necessary condition can also be a sufficient condition and visa versa, right? In order for them to happen at the same time, I need to conceptualize the event co-occurring in my head. Is this correct?

Re: How can a sufficient and necessary condition occur at the same time??
« Reply #4 on: August 17, 2007, 09:36:36 PM »
Are there any statistics that speak to how often sufficient and necessary conditions occur simultaneously on the LSAT?

Re: How can a sufficient and necessary condition occur at the same time??
« Reply #5 on: August 17, 2007, 09:50:34 PM »
No, nothing in particular. I was just wondering. There seems to be a statistic for everything else! I feel confident in recognizing the relationship between the two conditions. The LSAT testmakers are real tricky in describing the conditional relationships. I have been learning the LRB strategies. Are there any other strategies out there that are helpful and easy to understand?

mantis

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Re: How can a sufficient and necessary condition occur at the same time??
« Reply #6 on: August 17, 2007, 10:48:39 PM »
I don't recall any conditions on the LSAT that were both sufficient and necessary. 

Mabye an AB Block on the games would count. (A->B, B->A, so AB Block.) 

If you wanted to diagram it, just put the arrow going both ways.  But a block makes more sense.

But you're unlikely to see this on LR.

If you do see it on LR, it will probably be in the form of "if and only if" (ie. both sufficient and necessary).

Re: How can a sufficient and necessary condition occur at the same time??
« Reply #7 on: August 18, 2007, 03:00:10 AM »
I'm still not sure if Lawness is asking if a necessary condition and a sufficient condition can happen simultaneously (meaning that if these things were really happening, could they happen at the same time or does one have to come first), or if (s)he's asking if a necessary condition can also be a sufficient condition and vice versa--but here's something that might help regardless.  Logically speaking, 'necessary' and 'sufficient' are pretty much technical terms that refer to the logical relationship between two sentences/ideas, rather than to the actual relationship of whatever is being discussed.  In other words, here's a sentence:

If I have gas in my tank, then my car will run.

Even though in real life, it would be more accurate to say that gas is necessary for my car to run, in that sentence 'gas in my tank' is the sufficient part and 'my car will run' is the necessary part.  This is because 'necessary' just means "this is necessarily true if the other part is true"--which is what the conditional means.  And 'sufficient' just means "the truth of this statement is enough to guarantee the truth of this other statement".  The two statements that make up a conditional don't have to have any sort of realistic relationship at all--I can slap any two statements or ideas together and form a conditional, and one part will still be the sufficient part and the other the necessary part--so it might be easier not to think about how the statements are related to eachother in a real-life sense--because all any conditional really means is "if this is true, then that is true" -- why or how they are related to each other doesn't matter at all.

Re: How can a sufficient and necessary condition occur at the same time??
« Reply #8 on: August 18, 2007, 08:37:19 AM »
I'm still not sure if Lawness is asking if a necessary condition and a sufficient condition can happen simultaneously (meaning that if these things were really happening, could they happen at the same time or does one have to come first), or if (s)he's asking if a necessary condition can also be a sufficient condition and vice versa--but here's something that might help regardless.  Logically speaking, 'necessary' and 'sufficient' are pretty much technical terms that refer to the logical relationship between two sentences/ideas, rather than to the actual relationship of whatever is being discussed.  In other words, here's a sentence:

If I have gas in my tank, then my car will run.

Even though in real life, it would be more accurate to say that gas is necessary for my car to run, in that sentence 'gas in my tank' is the sufficient part and 'my car will run' is the necessary part.  This is because 'necessary' just means "this is necessarily true if the other part is true"--which is what the conditional means.  And 'sufficient' just means "the truth of this statement is enough to guarantee the truth of this other statement".  The two statements that make up a conditional don't have to have any sort of realistic relationship at all--I can slap any two statements or ideas together and form a conditional, and one part will still be the sufficient part and the other the necessary part--so it might be easier not to think about how the statements are related to eachother in a real-life sense--because all any conditional really means is "if this is true, then that is true" -- why or how they are related to each other doesn't matter at all.


I was really asking if they can occur in real life terms simultaneously because I was trying to make sense of the two with a real world example. It helps to think of the two instances/events in logical terms and without subscribing meaning to them. For diagramming purposes, the sufficient condition ALWAYS comes first, right? At least that is what LRB says.

Re: How can a sufficient and necessary condition occur at the same time??
« Reply #9 on: August 18, 2007, 01:55:46 PM »

Does a sufficient condition always come first in the construction?  Or can a necessary?  For instance:

SUFFICENT                    NECESSARY

If I have gas in my tank     Car will run

Car will run                 If I have gas in my tank

The phrase attached to "if" (and here I mean "if", not "only if"--"only" indicates the necessary part) is the sufficient condition, regardless of where that phrase appears in the sentence when it's phrased in words.  So in the second one above, "gas in my tank" is still sufficient.  But if you change it to:

If my car will run, then I have gas in my tank.

Then "my car will run" is now sufficient.  But the sentence now means something different.  Basically, the order the statements are given doesn't matter:

If I have gas in my tank, my car will run.
My car will run if I have gas in my tank.
I have gas in my tank only if my car will run.
Only if my car runs do I/will I/must I have gas in my tank.

In all of these, "gas in my tank" is the sufficient part, and "car will run" is the necessary part.

If you symbolize it:

G --> R

then what's to the left of the arrow is sufficient, and what's to the right of the arrow is necessary, always.