We are told that if a scientific theory is a good theory, then it must accurately describe a large class of observations in terms of a model that is simple enough to contain only a few elements, AND it must make definite predictions about the results of future observations.
P1: GT ==> DLG and MDP not DLG or not MDP ==> not GT
We are told that Aristotle's theory did not make any definite predictions:
P2: not MDP
Thus, it was not a good theory.
C: not GT
This is a valid argument. We are tasked to choose the answer choice that must be true except, i.e. that could be false.
Answer choice (A) states that any good scientific theory must make predictions about the results of future observations. Well, if we take the statements in the passage to be true, we know that this must be true because "P1" tells us that a good scientific theory needs both "DLG" and "MDP."
Since we are taking all the statements in the passage to be true, we know that Aristotle's cosmological theory satisfied the first requirement of accurately describing a large class of observations in terms of a model that is simple enough to contain only a few elements and we know that it did this by claiming that everything was made out of four elements--earth, air, fire, and water. Thus, answer choice (C) must also be true.
Answer choice (D) states that a scientific model that contains many elements, i.e. does not accurately describe a large class of observations in terms of a model that is simple enough to contain only a few elements, i.e. not DLG, is not a good theory. We know from the contrapositive of "P1" that if we do not have DLG, then we do not have a good theory. Thus, answer choice (D) must be true, as well.
Answer choice (E) states that Aristotle's cosmological theory described a large class of observations in terms of only four elements. We know this must be true because the passage tells us that this theory claims that "everything was made out of four elements."
Which leaves us with answer choice (B).
Answer choice (B) discusses Aristotle's major concerns. Nowhere in the passage do we discuss any type of concern held by Aristotle. We are only told about his cosmological theory and what it entailed. Thus, because we never discuss Aristotle's concerns, we are not given sufficient information to deduce that answer choice (B) could be true or false. Thus, answer choice (B) does not necessarily have to be true, i.e. it could be false. So, it is our correct answer!
Hope that clears things up! Please let us know if you have any other questions.
mak16153November 9, 2019
Shouldn't premise 1 be:
DLG and MDP ==> GT
not GT ==> not DLG or not MDP?
erica-scottAugust 3, 2020
Wouldn't C not be true because the passage said that "Aristotle's cosmological theory was not a good theory"?
Further, doesn't C fulfill DLG but not MDP - which would make it not a good theory?
shunheAugust 4, 2020
Hi @mak16153 and @erica-scott,
Thanks for the question! So first, to answer the question of what the first premise should be: it’s actually both what you said and what Naz said! The first sentence is actually an “if and only if” type sentence, and so the arrow goes both ways. We can diagram it
DLG & MDP <—> GT
Which means ??DLG & MDP —> GT GT —> ~DLG v ~MDP
and also
GT —> DLG & MDP ~DLG v ~MDP —> ~GT
And the reason we know this is true is because we’re told that “If these REQUIREMENTS are satisfied, it’s a good theory.” So the things that are the requirements are both in the sufficient (because of the “if”) but also the necessary (because they’re requirements).
As for (C), it does have to be true. And that’s because (C) doesn’t say anything about a good theory! (C) says that “four elements can be the basis of a scientific model that is simple enough to meet the simplicity criterion of a good theory.” And Aristotle’s theory, as you seem to have noted, has four elements. Now, what’s the simplicity criterion of a good theory? It’s that it must accurately describe a large class of observations in terms of a model that is simple enough to contain only a few elements, in other words, DLG! And as you noted, Aristotle’s theory fulfills DLG! So Aristotle’s theory, which has four elements, can meet the simplicity criterion, even if it didn’t meet the other criterion. And so that’s why (C) must be true.
Hope this helps! Feel free to ask any other questions that you might have.
