I was meticulous in writing each of the premises because I tended to write them down wrong. Then just followed them logically and did the contrapositive of x then z.
jakennedyJanuary 19, 2022
Hi all,
This is an argument completion drill that corresponds with the strengthen with the must be true question type when it contains conditional logic. Your job is to make inferences from the premises.
Let’s start with premise 1.
P1: X ? A
Now we want to combine this with the other evidence. To do so, we have to find common elements, so either X or A. Premise 3 has neither of these, so look to premise 2. Premise 2 has not A, but premise 1 has A. This won’t work. You need them both to be A, or both to be not A. Whenever this happens, you can fix the problem by simply taking the contrapositive of premise 2 so it matches:
P2: not B ? not A Contrapositive A ? B
Now that it matches, we can see how it works with premise 1:
X ? A ? B
Premise 3:
P3: B ? Z
Adding premise 3 to our diagram:
X ? A ? B ? Z
and its contrapositive:
not Z ? not B ? not A ? not X
On these flashcards, the answer will include the endpoints, so X ? Z or not Z ? not X. Most must be true questions will as well, but they do not have to. The answer could be, say, if A then Z, or if not B then not X. As long as it must be true according to your diagram it the correct answer.
