I keep falling for the "oldest trick in the book" - sufficiency/necessity LR questions

ecarr_12ecarr_12 Monthly Member

At first, it was quite easy for me to identify and correctly label conditional statements. But, now that I am nearly 60% through with the CC (currently working with flaw questions) and questions are no longer in the "identify" phase, but, rather, have increased into the difficult world of description and analyzation ... I find myself getting tripped up with the direction of my statements (confusing necessity for sufficient, and vice versa). I realize that I need to now slow down my progression with the CC until I am able to really drill this concept in my head. Any suggestions/advice/tips/examples (preferably harder examples) would be greatly appreciated!


  • AlexAlex Alum Member
    23929 karma

    Hey @escarr_12 ,

    If you're having any issue with confusion of necessary/sufficient, I would simply recommend going back to the basics and reviewing those lessons. These are too important and there's really no good substitute then just making sure you fully understand these.

    Necessary assumptions are those that are necessary or allow the argument/conclusion to occur. It alone is not enough to guarantee the conclusion. A good way to test necessary assumption questions is to negate them. When negated if they argument/conclusion becomes impossible to occur, then it is in fact a necessary condition.

    Sufficient assumptions are enough to guarantee or prove the conclusion. Sufficient assumption statements are usually written as conditional statements whereas necessary assumptions are generally not.

    Like you said, it's probably best to slow down with the CC for now and drill and learn these concepts. I wish there were some better tips I could think of, but I truly think JY's lessons and examples are more helpful.

    Do let me know if there are specific things you are getting confused with?

  • patrickfollispatrickfollis Free Trial Member
    20 karma

    Greetings @ecarr_12 ,

    In order for JY to record a tutorial video, he must snort three hefty lines of crack cocaine. If JY is instead doing weed, then he is not recording a video. Let me explain.

    In the first scenario, we see that a condition that must be met in order for JY to record a video is the consumption of cocaine. No other requirements are listed, and for all we know he must be high on bath salts and other goodies in addition to the crack. We simply don't know. But, we do know one necessity to record a video is 7sage premium cocaine. It is a necessary assumption.

    In the second sentence, JY doing weed and him not recording a video are directly connected with an if/then structure. The two are linked closer, and knowledge of an herbivorous JY is enough to know he is also not recording. However, keep in mind that although it is true if we know JY is on weed he must also not be recording, we cannot say for certain that if he isn't recording he is definitely on weed. Other causes may be responsible. Nevertheless, this is a sufficient assumption.

    Simply put, both necessaries and sufficient only work one way. Knowing the conclusion occurred does not guarantee the assumption. The difference is, knowing a necessary assumption took place does not guarantee the conclusion, but knowing a sufficient assumption to be true does.

    I also recommend JY's videos ;)

  • ecarr_12ecarr_12 Monthly Member
    179 karma

    Thank you so much ! @"Alex Divine" and @patrickfollis for your especially entertaining example haha. I reviewed some of the early core lessons and read through a multitude of comments from equally frustrated 7 sagers and realized that my problem was due to how my mind translates English to lawgic and then back to English again. I was accustomed to thinking in an if "x" then "y" manner ... As has been shown in harder questions, statements are rarely this easy to parse and do not follow this if/ then structure. Now that I am framing conditionals based off of a "guarantee" relationship - (X guarantees Y. Y on its own tells us nothing. If /Y then we can guarantee /X) my confusion has largely been cleared. But, of course, re-wiring a conditioned way of thinking is going to require more practice and exposure.

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