What variable comes first in missing premise or conclusion?
Hi! I am confused on how to know which variable comes first in a missing premise or conclusion. I chose C -> B rather than B -> C. In questions using this format I often get confused on which variable is supposed to come first. Please advise!
If there are any lectures I should rewatch please let me know because when I do missing premise or completion drills its often just me guessing and I Don't understand why I got them wrong.
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This is a type of notation that the course uses. While it is a fairly common way to diagram If/Then statements, you should find a style of notation that works best for you.
C -> B is the way that the flashcards denote the statement "If C then B" B -> C denotes "If B then C"
The lecture videos should use this notation as well.
libbygarfootJune 25, 2022
Hi, thank you! I'm not actually confused on the notation style. I am confused on the method of finding a missing premise. I know how to find the contrapositive of each premise and the conclusion but finding the missing premise is hard for me. Often times I can narrow down whether the variable should be negated but then don't know which one to put first.
Emil-KunkinJune 26, 2022
Hi Libbygarfoot,
To find a missing premise we are looking to find what would make the conclusion valid.
If we are told that all dogs are good, so therefore some pets are good, we would need to find the thing that, if added, would justify the conclusion that some pets are good. That is, that at least some dogs are pets.
I would try to think about these drills in terms of more concrete things rather than X and Y. These are arguments that we are trying to make valid, and might be easier to think about them as dogs and cats, or senators and presidents rather than abstract terms.
