Just a stupid question about sufficient necessary assumption

 Posts: 45
 Joined: Wed Apr 17, 2013 5:22 pm
Just a stupid question about sufficient necessary assumption
This might be stupid. So, I thought of this "theory?" or question rather about necessary and sufficient assumptions: Suppose we have an argument that, for one reason or another, we know has 100 necessary assumptions. Suppose the 99th and 100th assumptions were A and B. Suppose A was the 99th assumption, wouldn't that automatically make B the sufficient assumption? And, on the other hand, if B was the 99th, then A would be the sufficient. In other words, if we could theoretically plug in the very last necessary assumption, that very last assumption would be the sufficient. Right or right? I know it sounds stupid for most of the advanced folks or for those who don't get it.
 Balthy
 Posts: 668
 Joined: Sat Apr 03, 2010 12:28 pm
Re: Just a stupid question about sufficient necessary assumption
Why would assumption 99 have to be assumption 99 instead of 100? If, for example, the stimulus is arguing for an explanation of a certain phenomenon and is assuming that other alternate explanations are false, then there is no chronology to those assumptions, they're simply all necessary assumptions. So, if there were two answer choices that were negations of possible alternate explanations, it wouldn't make sense to label one the 99th and the next the 100th. For the sake of argument though, sure, if you knew that all other nec. assumptions for an otherwise good argument were dealt with and there was just one left, it would technically be sufficient.

 Posts: 45
 Joined: Wed Apr 17, 2013 5:22 pm
Re: Just a stupid question about sufficient necessary assumption
superdingle2000 wrote:Why would assumption 99 have to be assumption 99 instead of 100? If, for example, the stimulus is arguing for an explanation of a certain phenomenon and is assuming that other alternate explanations are false, then there is no chronology to those assumptions, they're simply all necessary assumptions. So, if there were two answer choices that were negations of possible alternate explanations, it wouldn't make sense to label one the 99th and the next the 100th. For the sake of argument though, sure, if you knew that all other nec. assumptions for an otherwise good argument were dealt with and there was just one left, it would technically be sufficient.
No chronology needed; those are just examples.
 Balthy
 Posts: 668
 Joined: Sat Apr 03, 2010 12:28 pm
Re: Just a stupid question about sufficient necessary assumption
Journey180 wrote:superdingle2000 wrote:Why would assumption 99 have to be assumption 99 instead of 100? If, for example, the stimulus is arguing for an explanation of a certain phenomenon and is assuming that other alternate explanations are false, then there is no chronology to those assumptions, they're simply all necessary assumptions. So, if there were two answer choices that were negations of possible alternate explanations, it wouldn't make sense to label one the 99th and the next the 100th. For the sake of argument though, sure, if you knew that all other nec. assumptions for an otherwise good argument were dealt with and there was just one left, it would technically be sufficient.
No chronology needed; those are just examples.
Some sense of "disarming" A is needed in your example in order to make B not only nec. but sufficient. It seemed to me that the chronology you mentioned was expressing that idea. If it wasn't, then no, B would not become sufficient.

 Posts: 136
 Joined: Sat May 11, 2013 2:25 am
Re: Just a stupid question about sufficient necessary assumption
It depends. From what you're saying, I think you may have the wrong idea of necessary and sufficient assumptions.
The keyboard costs $20. I can buy the keyboard.
What necessary assumption would make this argument true?
Necessary assumptions that would work:
1) I don't have only $5.
2) I don't have between $10 and $15.
3) I do have money.
What sufficient assumption would make this argument true?
Sufficient Assumptions that would work
1) I have exactly $20.
2) I have more than $20.
3) I have $100.
Take Sufficient Assumption number 2. Notice that even though it might be enough for you to have more than $20 for this argument to work, it's not actually needed/REQUIRED for you to have more than $20.
Hopefully this helps you with necessary and sufficient assumptions.
But also, take a look at those 3 necessary assumptions we have up there. (Compare it to your 99th and 100th example). We can accept the first two assumptions as is. Now look at the third. How is this automatically a sufficient assumption? It's not. It's not enough to say that you have money and expect the argument to work. It surely is NEEDED, but it's not ENOUGH.
And as Superdingle2k is trying to say, also realize that necessary assumptions do not have a particular list to them. Notice how you can switch any one of these 3 necessary assumptions around and it still wouldn't matter. So to say that the "last" assumption of your necessary assumption list is somehow a sufficient assumption, makes me feel that that there must have been a bit of confusion during your studying of assumptions.
ALL necessary assumption are NEEDED for the argument to work.
There's no guarantee that any one of these that we choose is ENOUGH, although it is possible.
E.G.
Example of another Necessary assumption:
1) I have at least $20.
In this case, the necessary assumption would also pass as a sufficient assumption. We NEED to know that we have at least $20 to buy that keyboard. It also happens to be that this assumption is ENOUGH for the argument to work (making it a sufficient assumption).
Soo uhh. I hope what I wrote helps.
The keyboard costs $20. I can buy the keyboard.
What necessary assumption would make this argument true?
Necessary assumptions that would work:
1) I don't have only $5.
2) I don't have between $10 and $15.
3) I do have money.
What sufficient assumption would make this argument true?
Sufficient Assumptions that would work
1) I have exactly $20.
2) I have more than $20.
3) I have $100.
Take Sufficient Assumption number 2. Notice that even though it might be enough for you to have more than $20 for this argument to work, it's not actually needed/REQUIRED for you to have more than $20.
Hopefully this helps you with necessary and sufficient assumptions.
But also, take a look at those 3 necessary assumptions we have up there. (Compare it to your 99th and 100th example). We can accept the first two assumptions as is. Now look at the third. How is this automatically a sufficient assumption? It's not. It's not enough to say that you have money and expect the argument to work. It surely is NEEDED, but it's not ENOUGH.
And as Superdingle2k is trying to say, also realize that necessary assumptions do not have a particular list to them. Notice how you can switch any one of these 3 necessary assumptions around and it still wouldn't matter. So to say that the "last" assumption of your necessary assumption list is somehow a sufficient assumption, makes me feel that that there must have been a bit of confusion during your studying of assumptions.
ALL necessary assumption are NEEDED for the argument to work.
There's no guarantee that any one of these that we choose is ENOUGH, although it is possible.
E.G.
Example of another Necessary assumption:
1) I have at least $20.
In this case, the necessary assumption would also pass as a sufficient assumption. We NEED to know that we have at least $20 to buy that keyboard. It also happens to be that this assumption is ENOUGH for the argument to work (making it a sufficient assumption).
Soo uhh. I hope what I wrote helps.

 Posts: 11
 Joined: Tue Jul 02, 2013 1:13 am
Re: Just a stupid question about sufficient necessary assumption
This is what I understand your question to be: If there are a finite amount of assumptions needed (exactly 100) and given that there are 99 Necessary assumptions, must the 100th assumption be Sufficient?
Here is an example, which I think you are getting at:
Argument: The chocolate bar costs $1.00. Yay, I can afford it.
A Necessary assumption is something that can help close the gap in the core. So a Necessary assumption would be: “I have at least fifty cents.” As you can see, having at least fifty cents is needed (necessary) for my argument to work.
A Sufficient assumption is something that will perfectly/excessively close that gap. An example: “I have $1000.” Therefore, I definitely can afford that chocolate bar, a milkshake to go with it, and then some.
Using the same argument above to answer your question (if I had 99 necessary assumptions, what would the 100th assumption be sufficient or necessary?), I would say that if we state that the first assumption is “I have exactly 1 cent,” and the second assumption is that I have exactly 2 cents, and so on…. and the 99th assumption is that I have exactly 99 cents, then the 100th assumption would be that I have exactly 100 cents or that I have $1.00. Since the argument does not state anything about taxes, this 100th assumption would be sufficient. So in this example using currency, something that is easy to keep track of, that last assumption is sufficient.
Let me know if this was not helpful at all.
Here is an example, which I think you are getting at:
Argument: The chocolate bar costs $1.00. Yay, I can afford it.
A Necessary assumption is something that can help close the gap in the core. So a Necessary assumption would be: “I have at least fifty cents.” As you can see, having at least fifty cents is needed (necessary) for my argument to work.
A Sufficient assumption is something that will perfectly/excessively close that gap. An example: “I have $1000.” Therefore, I definitely can afford that chocolate bar, a milkshake to go with it, and then some.
Using the same argument above to answer your question (if I had 99 necessary assumptions, what would the 100th assumption be sufficient or necessary?), I would say that if we state that the first assumption is “I have exactly 1 cent,” and the second assumption is that I have exactly 2 cents, and so on…. and the 99th assumption is that I have exactly 99 cents, then the 100th assumption would be that I have exactly 100 cents or that I have $1.00. Since the argument does not state anything about taxes, this 100th assumption would be sufficient. So in this example using currency, something that is easy to keep track of, that last assumption is sufficient.
Let me know if this was not helpful at all.
Return to “LSAT Prep and Discussion Forum”
Who is online
Users browsing this forum: blackmamba8 and 17 guests