An assumption....depends? Woohooo! A necessary assumption question. You know the drill, conclusion, premises, gap (ask yourself why is the conclusion not necessarily true?), prephrase something that must be true if the author's conclusion
can possibly be true, then move to the answers.
Let's get the ball rolling and identify the conclusion, premises, and the gap between them. I'll represent the first two with a diagram, then I'll talk some more about the gap:
Argument Structure
View1: Horoscopes define our personalities
(1) Records establish that two people born with the same birthday and time of birth have different personalities
________________________________________________________________________
CONCL: View1 is false
You'll notice that I left out a couple phrases in the premises, let me explain why. I left out the second sentence, because it doesn't really contribute to the author's conclusion, instead by conceding this point, the author supports View1. I also left out the location element of the premise in the third sentence because it's descriptive information---is it important? Yes. But I left it out of the structure because I wanted the bare bones of the argument. I'll bring it up it in the next step.
The Gap: Why the Conclusion is not necessarily true
So we have a common method of reasoning (A view is introduced, then refuted based upon a premise that seems to establish an exception to the rule mentioned in the view). The gap, in this situation will always be related to the premise and whether or not it truly renders the view not necessarily true. Let's look a little closer:
Our premise is drawn from records and our conclusion (that View1 is false) related to horoscopes. Notice that our premise doesn't explicitly establish that the people mentioned in the records have the same horoscope---that's the assumption. Now if we were to attack this argument, we would likely point out that these records may be flawed in some way, or that even if these records are true, the fact that two people were born at the same time, and on the same day, doesn't necessarily mean they have the same horoscope.
Side note: I really don't know much about horoscopes. I seem to remember that they might be related to the month in which a person was born, but I'm not really even sure that's always the case. I'm totally ok with that, because what I do know is that there's a shift in scope in this argument based upon what is sufficient for the same horoscope. And I know that's the case because unless something is explicitly stated in an argument, then it's assumed to be true, and that's exactly what's going on here.
So the issue is whether the two individuals mentioned in the records have the same horoscope and this turns on whether the time and date of birth are the only relevant factors in determining a person's horoscope.
If either of these things are not true, then the conclusion doesn't necessarily follow from the premises because where two people have different horoscopes, or where they don't necessarily have the same horoscope, the conclusion (that View1 is false) is far from certain. In fact, if either of these facts are wrong, then the view the author is trying to weaken is supported, not refuted, because in that case we would have people with different horoscopes (or not necessarily the same horoscope) and different personalities, which follows from the causal view the author is trying to weaken.
Now let's look at your question:
agp2111 wrote:My question: How can I identify this assumption in the argument? When I read the argument, I thought, "Well, if two individuals have different personality types, but born at the same time, they can still have the same horoscope. Perhaps a horoscope produces a variety of personality types different from another group of personality types produced by another horoscope."
Is that a fair assumption for me to make? How do you think I could have gone out identifying in advance the assumption of the correct answer choice?
Well it's important to note that the author essentially says that some thing
A doesn't always completely determine
B. The view the author is trying to counter in simpler form is that
A causes
B on it's own. To weaken this the author attempts to show that
A does not result in
B all the time.
The author tries to establish this by using an example of something that appears to fit the definition of
A, and does not result in
B. Thus, the issue is whether the author's example actually does match the cause stated in the view he is trying to refute. Because if it does, if the author's example is the same as the stated condition in the view he is refuting, and since his example produces different effects, then his position is correct. But if not, if the author's example does not produce the same condition in the view he is refuting, then his conclusion doesn't follow from the premises.
The bolded phrase in quotes above, is precisely the issue. Maybe the fact that two people were born at the same time and on the same day does produce the same horoscope for those people, BUT THE AUTHOR HASN'T ESTABLISHED THAT!
I didn't really get into the answers, but based upon a brief skim of them, the right one jumps off the page, B might be a contender but it's also pretty easy to dismiss. If you want a bit of analysis on the answers, just let me know.
Does this shed some light on your question?
