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Related Discussions
Valid Argument Forms
miriaml7
Live Member
I am currently struggling to move past the CC lessons on valid argument forms. With the use of flashcards, I have been able to memorize what the abstract form of each valid argument form looks like. For example, if I am given the premise A-->B and the conclusion B some C, I automatically know that the missing premise needed to restore this argument to validity is A --> C. However, when I see this same valid form in English as opposed to logic I compltely freeze. I have tried writing out my own English statements for each of the valid argument forms. Doing this helped me see how cookie-cutter the valid argument forms are. However, I feel like once I see these argument forms on the LSAT it will not be as cookie-cutter. For example, I recently realized that when I was writing out my own English statements I had failed to take into account that the fact that you can move around premises and still get a valid argument form. For example:
Premise 1: O→K
Premise 2: J‑m→O
Conclusion: J‑m→K
By simply looking at this argument's abstract form, I know that it's a valid argument. It embodies valid argument 5. In the example above, A‑m→B was switched into premise 2 and B→C was switched into premise 1. However, when I see this switch being applied in English, my brain turns into mush. Continuing with the example from above, the English translation would sound something like:
All octopuses are kind. Most people named James are octopuses. Most people named James are kind.
Octopuses= O
Kind=K
James=J
Right??
I am aware that on the LSAT, the topics in the stimulus questions that require your understanding of validity are going to be a lot more challenging. That's why I am looking to get some insight in terms of how to solve this issue. I really appreciate your time!
Comments
It seems as though you are taking a very thorough approach to memorizing and understanding the valid argument forms, which I commend you for. Knowing those inside and out will definitely help you. Based on what you’ve said above (your octopus example is correct by the way) I would suggest you just keep practicing what you’re doing. Additionally pick out conditional logic intensive questions and analyze how they present the valid/invalid argument forms in English. Once you’ve got the forms down, you will notice that the difficulty arises solely from the complex use of English.
Good luck! You got this!
@Logician Really great idea! Thank you!
Hi M! I don't think your first example in your explanation is correct, > @miriaml7 said:
Keep going over the examples JY uses, what really helped me grasp the concept is the "bucket idea" It's definitely a contortion of thinking and it is tough. If all A's are B's and the conclusion is some B's are C's, all A's are C's would not make this argument valid. Its actually invalid. The some or most statements have to be in the sufficient condition, not the necessary condition. and The arrow and the most statement only go one way, they aren't biconditional. If you pour all A's into B and then grab a handful of that and put it into C, then there's more than a small chance you wont grab any A's, so you can't say with certainty that there are going to be any A's in C. I'd say Illustrate the concept, think of cups of A's, B's or Zebras. Watch the videos again and pause them and write it out yourself. You'll get it!
@audieya @miriaml7 you are mistaken, miriam's first example is correct. if we have A-->B and the conclusion is B some C, A-->C would most certainly make this a valid argument.
A-->B
A-->C
B some C
This is a valid argument. Specifically, its valid argument form #6. However, we could also bridge the gap by adding the premise A some C or A most C.
@audieya I really appreciate your encouragement!
In all honestly I don't have a firm understanding of the bucket method:( I tend to resort to the list method instead. Using the list method, I think A-->B and A-->C in the premise would lead to the valid conclusion of B some C:
Let's say we live in a world where there are exactly 5 As:
Based on the premise, we know that A--->B (i.e. all As are Bs, so anytime we see an A there must be a B
1.AB
2.AB
3.AB
4.AB
5.AB
There is the possibility that in our hypothetical world there are some things that are Bs, but are not As:
B
1.AB
2.AB
3.AB
4.AB
5.AB
B
Based on the second premise, we know that A-->C (i.e. all As are Cs, so anytime we see an A there must be a C)
1.CAB
2.CAB
3.CAB
4.CAB
5.CAB
Similar to premise 1, there is also the possibility that in our hypothetical world there are some Cs that are not As :
C
C
C
1.CAB
2.CAB
3.CAB
4.CAB
5.CAB
All in all, the list method shows an intersection between Cs and Bs exists. Therefore, some Cs are Bs , which as you pointed out earlier, is the same thing as saying some Bs are Cs.
I apologize in advance if my explanation wasn't clear at some point. If you have any feedback for me, I would definitely appreciate it:)
At one point, I thought that I would be fine by just being able to have seen the valiid argument forms and be able to mostly recognize them. I came to the understanding that eventually being able to figure out a argument is invalid is not good enough when someone else can see the same statement and figure that out in 30 seconds. Like you, I made flash cards with both valid and in valid forms. But, I also made examples of each of those and made them into flashcards as well. I reviewed them daily, multiple times a day for a good month. The Flash card stack got bigger as whenever I found examples of these argument forms in questions I made them into flashcards as well, sometimes multiple flashcards. To give you an example, if I saw a parallel reasoning question that used invalid reasoning, I would put on the front of the flash card, the stiumulus and then I would put underneath, what argument form? I expected to be able to recall the argument form. I also made some of them into flashcards, where I put the stimulus and a couple of the most attractive answer choices ( at least one wrong, and the right one). By exapanding my application I not only got exposure to the valid and invalid argument forms but I also got more and more comfortable with LSAT language and being able to recognize trap answers. I added other things eventually to my flash cards, but using them to truly understand argument forms has been a big purpose of the flashcards. Even now, months later I occasionally add to my flash card set.
@FindingSage I really appreciate you sharing this! Thank you!
@miriaml7 Your welcome! The flashcards have helped me more than I ever expected they would. Aside from the valid and invalid argument forms and questions relating to them I also created a lot of flashcards for flaws. That really helped me being able to get some questions answered both quickly and confidently so that I had the time to be able to be able to map out more logic heavy questions.
Thanks for the clarification. I typed my response under a false assumption that the A most C was in the necessary condition. Duh. She clearly wrote conclusion. I apologize for adding to the confusion.
Writing out the explanation pushed me to test my understanding of validity, so thank you for that:) @audieya