Self-study
Hello, newb here!
Struggling with sufficient necessary, went through lesson a few times.
Do I understand this so far?
Apple---->Fruit
Apple is a sufficient condition to be a fruit
Fruit is a necessary condition to be an apple
Whats next to complete my understanding?
Thanks in advance for further elaboration and help! :)
S
1
2 comments
Yes, you're right about the example you gave -- being an apple is sufficient (i.e. enough to guarantee) that something is a fruit. In other words, being a fruit is necessary (i.e. required) for something to be an apple. At a conceptual level, we can also think of this as "If something isn't a fruit, it isn't an apple." That's called reasoning by the contrapositive: since apple --> fruit, then /fruit --> /apple. I'd say it could be helpful to get comfortable contraposing logical relationships -- first in the real world (e.g. dog/animal, chair/furniture, water/liquid, etc.), then with more abstract symbols. After that, practice representing sufficient and necessary conditions symbolically using circles. Sticking with the apple/fruit example, "apple" would be a circle that is surrounded by the bigger circle of "fruit." These circles show you something important: it is possible to be within the necessary condition (i.e. be a fruit) without being inside the sufficient condition (i.e. being an apple) and likewise that being outside the outer circle ("fruit" circle) guarantees that you are also outside of the inner circle ("apple" circle). Visually, sufficient conditions are inner circles and necessary conditions are outer circles. I think knowing both the symbolic and the visual ways to represent sufficiency and necessity is really useful groundwork for understanding a lot of LSAT question types and logical flaws.
And as an additional challenge, you can start working with several conditions at once to see how "sufficiency" and "necessity" are relative terms that depend on the conditions you are referring to. For example, "person" is sufficient for "organism," which is sufficient for "living." Therefore, "living" is necessary for "organism," which is necessary for "person." So /living --> /organism --> /person.