Self-study
Confusing necessary and sufficient conditions is a problem for me. I’m trying my hardest to understand conditional logic through videos but it’s not clicking. Does anyone know any other methods or tools I could use? I’m a visual learner.
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i know what you mean. sometimes i feel my brain gets stuck and having taken a 200 level logic class in college still didn't help me. The purpose of having to use conditionals is different.
I always refer back to what i was first taught:
If it rains (Sufficient) then the floor is wet (Necessary)
If it does not rain, does the mean that the floor can still be wet? yes! a hose went off, someone peed, etc.
It does not have to necessarily rain in order for it be wet.
Sufficient condition -> necessary condition. If a sufficient condition is met, it will guarantee the necessary condition. For example, a person who works out will be fit (in lawgic: works out -> fit).
However, being in the necessary condition does NOT prove that you are in the sufficient condition. For the example, you cannot say that a person being fit means they work out. There can be other reasons (sufficient conditions) why this person is fit (maybe they eat really healthy or have a crazy fast metabolism).
Another way I look at necessary conditions is when they're required for an outcome. For ex, as the lecture videos showed, a practicing lawyer MUST take the bar exam. There is no other way around this - it's necessary. In lawgic: practicing lawyer -> bar exam. However, if you switch these around (bar exam -> practicing lawyer), it doesn't work because there are other requirements for being a practicing lawyer so meeting the bar exam alone does not mean you automatically become a practicing lawyer.
I hope this helps!
So I think I can help with this but my way of understanding it may be a little silly so to avoid embarrassment just dm me lol
https://www.sfu.ca/~swartz/conditions1.htm
I read a lot of different explanations, the link above explained it in a way that made sense to me.
TLDR:
Existence of the sufficient condition GUARANTEES the necessity condition
Absence/Failure/Falsity of necessary condition GUARANTEES the Absence/Failure/Falsity of the sufficient condition
This is not true the other way around
i.e.
failed sufficient tells us nothing about the necessity
present necessity tells us nothing about the sufficient
Easiest example for me to understand this is:
Human life -> oxygen
Human life guarantees presence of oxygen
No oxygen guarantees no human life
no human life (failed sufficient) = don't know about oxygen
oxygen (present necessary) = no idea if human life exists
This example is taken straight from the page referenced above
Best of luck
@Taylor345 You are a godsend! Thank you so much for that website and your explanation!!
It’s often felt like trying to find “simple” examples of logic problems/statements online is like trying to find a needle in a haystack (impossible for me). That site is going to be a perfect reference for me moving forward.
Such an awesome community here.
Have you looked up the venn diagram method of visualizing sufficient and necessary conditions?
When you hear sufficient, you should think "enough," as in "I have had sufficient food for today." So, the sufficient condition is the one that is enough to ensure the truth of the other condition.
When you hear necessary, you should think "needed," as in "Food is necessary for my survival." [In other words, if you take away the food, I will not survive.] So, the necessary condition is the one that is needed for the other condition to be true.
Example: If it is raining, then the streets are wet.
"It is raining" is the sufficient condition because it is enough to bring about the wet streets. (Notice that the rain is not needed to bring about the wet streets because the streets can be wet for other reasons.)
"The streets are wet" is the necessary condition because it is needed for the rain. That might sound kind of weird, but if you think about it, taking away the wet streets would mean that we also have to take away the rain. So, the wet streets are in fact needed for the rain.
In general, the "if" part of a conditional is the sufficient condition, and the "then" part is the necessary condition.
I can relate - I'm also a visual learner and having the information separated at different frames of videos on different pages did not help. And I also could not understand conditional logic until I took one day to write out the 4 major ones (using something amusing/easy to remember, which was my coworkers' work schedule lol) and just reread them over and over again until it clicked. Then, I reviewed conditional logic questions I already did (God bless 7Sage's filtering platform for all questions) and tried diagramming them again, now accurately. The next step was to not even bother writing anything down - what I do is highlight what's on the left side of the arrow if I was to diagram.
I'm still not fast at it, but at least I'm no longer scared.
the classes do a great job at reinforcing the curriculum.
It took me a little while too. I’d say to remember that necessary assumption means that it is needed for the argument to work, while sufficient assumption means it guarantees the conclusion (it proves the argument).
For example, only if you have a ticket you can go on the train, so Sarah must be on the train. The necessary assumption here is Sarah must have a ticket.
Another example is, if it is raining then we can’t go outside. It’s not raining, so we will be outside. The sufficient assumption here is that if it is not raining we are always outside.
For necessary I would try to see what the argument rests on, what must be there. Sufficient I’d look at the gap and see which answer choice most logically fills it.