surbhi1991 wrote:

Hi

How is B Not correct?

Also If we negate E, It doesn't negate the conclusion.

To understand the problem with answer choice (B), first take another look at the conclusion of the passage:

**Quote:**

it is impossible to know any mathematical proposition to be true.

Note that the conclusion deals exclusively with

mathematical propositions. Keep this in mind while reading answer choice (B):

**Quote:**

(B) Observation alone cannot be used to prove the truth of any proposition.

The key word in this answer choice is "

any." Answer choice (B) would apply to a broader range of propositions than just the mathematical propositions mentioned in the conclusion (artistic propositions, philosophical propositions, culinary propositions... or whatever). These other types of propositions are not relevant to the conclusion of the passage. Answer (B) does not provide any additional links between the evidence and the specific conclusion of the passage, so it is not an assumption upon which the author relies.

For (E), you don't really need to use the negation technique. (More on the limitations of the negation technique

here.) Instead, you could think of it this way: if (E) is assumed, will the conclusion logically follow from the facts given in the passage? Here's one of those key facts again:

**Quote:**

No mathematical proposition can be proven true by observation.

And here is answer choice (E), our potential assumption:

**Quote:**

(E) Knowing a proposition to be true requires proving it true by observation.

Now we know from the passage that mathematical propositions

cannot be proven true by observation. We also know that knowing a proposition to be true

requires proving it true by observation. It follows that "it is impossible to know any mathematical proposition to be true."

Answer choice (E) has provided the missing link between the evidence and the conclusion, and so it is the correct answer.

I hope this helps!

. The argument is about

. By saying a proposition, we are including all kinds of proposition which is not required by the argument. We need something bare minimum. What is your view on this?