Sometimes it's difficult to see whether an assumption answer choice is necessary to the argument, but easier to see what happens when that choice is ruled out. In other words,
if you want to double check whether your answer choice for an assumption
question is correct, DENY the assumption, and see what effect
that has on the argument. This is CAT's Denial Test, and although
it takes some practice, it can be very powerful.
Let's see how this would work with our argument about
Sally, the Central High School Volleyball player:
Sally plays volleyball for Central High School. Therefore,
Sally must be more than 6 feet tall.
Assumption:
All volleyball players for Central High are more
than 6 feet tall.
Assumption Denied:
All volleyball players for Central High are not
more than 6 feet tall.
What's the effect of denying this assumption? We are
no longer able to conclude that Sally is, without a doubt, 6 feet tall.
The argument is no longer valid when we deny the assumption, so that assumption
must be crucial to the argument.
Let's get some practice in using CAT's Denial Test.