Q9 - A scientific theory is a good

[ryyang1118]

For this question, I notice that when the stimulus introduces the two requirements (1. describe with only a few elements 2.make def. predictions), it uses both "if" and "must". I think it thus suggests that these two requirements are BOTH sufficient and necessary conditions for a scientific theory to be a good theory. Just want to confirm whether or not my understanding is correct...

Thanks

[ManhattanPrepLSAT1]

You're correct!

The word "if" in the first line establishes that any theory that possesses both qualities is a good theory. In the second line, the word "must" establishes that both qualities are requirements of any good theory.

So, yes. The way this stimulus is formulated, establishes that these two qualities are both sufficient conditions as well as necessary conditions of any good theory.

For anyone still struggling with this question...

The question stem asks us to find the answer choice that could be false.

(A) must be true. Prediction is one of the requirements of any good theory.
(B) could be false. We know that Aristotle's cosmological theory did make observations, however, we are not certain whether it was a major concern in Aristotle's theory. So, this answer could be false and is therefore correct.
(C) must be true. Aristotle's theory used four elements and it satisfied the simplicity criterion.
(D) must be true. A good theory contains only a few elements. So, one that contains many elements would not be a good theory. That said... I think they could have worded this one a bit better as the definition of many is simply "two or more." This would make me nervous, but it's early in the section, and it's clear what they meant to imply.
(E) must be true. This information is directly related in the stimulus.


Nice work in noticing the key words and how they create a biconditional relationship between the terms!

[damnsky]

Thanks Matt. I agree that the correct answer is B, but I have trouble to understand why A and D "must be true".

It seems to me that A is a false reversal of the original conditional statement, and D is a false negation of the original conditional statement. I don't know why A and D "must be true" if they can not be correctly derived from the text. Does this mean false negation and false reversal are all correct answers for "Must be True" questions?

What if the question asks for which one can be properly inferred from or which one is mostly supported by the passage? I always thought false negation or false reversal could be the correct answers for these 2 questions, but not for "must be true" questions.

[uhdang]

Same question as the post above.

Since this structure is such that:

A (able to explain large number of observation with a few elements)
+
B (Future prediction)
==>
C (A good scientific theory)

D) is showing Mistaken Negation form:
~ (A + B) ==> ~C
Many elements (Not small number of elements) ==> NOT good theory

I can see that there is no way to verify B) and it's could be false answer, but what do we do about D)? I'm having trouble making D) as Must Be True.
Help me out please.

[ohthatpatrick]

Just fyi (to the previous poster), "must be true" = "properly inferred".

"Most strongly supported" = "as close as I can get to must be true".

We would never want to pick illegal reversals or negations on any of those. The closest we ever come to doing so is when you know Cause X led to Effect Y, you might see a correct answer on "Most strongly support" that takes the form of "If X hadn't happened, it's less likely Y would have happened."

There's no way to get a mistaken negation or reversal here because we're dealing with a bi-conditional statement (it goes both ways). That's what the first two posts were talking about.

"If" is a sufficient condition. "Must" is a necessary condition.

IF Satisfy two requirements, THEN good theory.
(satisfy the two --> good theory)

A good theory MUST satisfy each of these requirements.
(good theory --> satisfy the two)

Putting those together, we know that
Good theory <----> satisfy the two
and when you write a 'contrapositive' to a bi-conditional, it doesn't matter whether you flip the sides, since the arrow goes both ways.
~Good theory <-----> ~satisfy the two

Bi-conditionals are really just either/or's.

Either you satisfy the requirements and you are a good theory
or you don't and you're not.

So (A) and (D) are just going off the "must".
good theory --> describes large class simply and makes predictions

~describe large class simply or ~make predictions --> ~good theory

Hope this helps.

[uhdang]

"If" is a sufficient condition. "Must" is a necessary condition.

IF Satisfy two requirements, THEN good theory.
(satisfy the two --> good theory)

A good theory MUST satisfy each of these requirements.
(good theory --> satisfy the two)

Putting those together, we know that
Good theory <----> satisfy the two
and when you write a 'contrapositive' to a bi-conditional, it doesn't matter whether you flip the sides, since the arrow goes both ways.
~Good theory <-----> ~satisfy the two

Completely unaware of Bi-conditional. This clarifies it completely.

Thank you.

[kenyamlee]

Hey, resurfacing questions about this problem.

The introduction of "if" followed by "must" has opened my eyes to how bicondtionals can sneak in. Glad to see I am not the only one confused and now awakened by this but I'm now questioning my interpretation of A and D. I am still aware that the stem poses a bi conditional, so either way the answer choices position the conditions, they must be true.

Is that what's being said ?

Can someone let me know if these diagrams are correct?

Question Stem:

"A scientific theory is a good theory if it satisfies two requirements:"
satisfies 2 requirements -- > good theory
A --> C {Contrapositive} -C --> -A
+ or
B -B

"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 definitive predictions about the results of the future"

good theory --> describe w/ few elements AND make definitive predictions....
C --> A {Contrapositive} -A --> -C
+ or
B -B

Answer Choice A:
Prediction about the results of future observations must be made by any good scientific theory.

any good theory --> Prediction abut the result of future observations
C --> B

(This is found true in the 2nd part if the stem)

Answer choice D:
A scientific model that contains many elements is not a good theory

contains many elements --> not a good a theory
-A --> -C
(Found true in the contrapositive of the stem)

Is this the right analysis?

Although after reading of couple of times and recognizing this is is a MBT EXCEPT question, I realize this was way easier. I still think having solid understanding and recognition of biconditional trickery would help also.

[ManhattanPrepLSAT1]

Hi kenyamlee, it's a bit unclear what your terms stand for.

"A scientific theory is a good theory if it satisfies two requirements:"
satisfies 2 requirements -- > good theory
A --> C {Contrapositive} -C --> -A
+ or
B -B

I think you're using the following letters to substitute for the terms of the argument:

A - good theory
C - describe a large class of observations in a model simple enough to contain only a few elements
B - make predictions about future observations

My suggestion would be to stop using A, B, and C and start using the letters of the terms your notating. It's typically much easier when you go to put things back into English to answer the question.

Here's notation that I might use.

Good Theory <--> Only a Few Elements + Make Predictions

(A) connects a good theory with one that makes predictions.
(B) contradicts the stimulus, which says that Aristotle's cosmological theory was concerned with describing a large class of observations.
(C) must be true since Aristotle's theory met the first requirement.
(D) is found in the contrapositive, as you point out kenyamlee.
(E) must be true since Aristotle's theory met the first requirement.

Hope that helps!