Critical Reasoning

Historian: Leibniz, the seventeenth-century
philosopher, published his version of calculus
before Newton did. But then Newton revealed
his private notebooks, which showed he had
been using these ideas for at least a decade
before Leibniz's publication. Newton also
claimed that he had disclosed these ideas to
Leibniz in a letter shortly before Leibniz's
publication. Yet close examination of the letter
shows that Newton's few cryptic remarks did
not reveal anything important about calculus.
Thus, Leibniz and Newton each independently
discovered calculus.

Which one of the following is an assumption
required by the historian's argument?

(A) Leibniz did not tell anyone about calculus
prior to publishing his version of it.
(B) No third person independently discovered
calculus prior to Newton and Leibniz.
(C) Newton believed that Leibniz was able to learn
something important about calculus from his
letter to him.
(D) Neither Newton nor Leibniz knew that the other
had developed a version of calculus prior to
Leibniz's publication.
(E) Neither Newton nor Leibniz learned crucial
details about calculus from some third source

IMO E:

E kills an alternate explanation that other than the letter they did not exchanged information through any other medium. SO E is an assumption that they didn't shared the info about the calculus.

gmatmachoman wrote:Historian: Leibniz, the seventeenth-century
philosopher, published his version of calculus
before Newton did. But then Newton revealed
his private notebooks, which showed he had
been using these ideas for at least a decade
before Leibniz's publication. Newton also
claimed that he had disclosed these ideas to
Leibniz in a letter shortly before Leibniz's
publication. Yet close examination of the letter
shows that Newton's few cryptic remarks did
not reveal anything important about calculus.
Thus, Leibniz and Newton each independently
discovered calculus.

Which one of the following is an assumption
required by the historian's argument?

(A) Leibniz did not tell anyone about calculus
prior to publishing his version of it.
(B) No third person independently discovered
calculus prior to Newton and Leibniz.
(C) Newton believed that Leibniz was able to learn
something important about calculus from his
letter to him.
(D) Neither Newton nor Leibniz knew that the other
had developed a version of calculus prior to
Leibniz's publication.
(E) Neither Newton nor Leibniz learned crucial
details about calculus from some third source

Before concluding that Newton and Libniz discovered they made sure that Newton didnt disclose anything to Leibniz which is clear from the line Yet close examination of the letter shows that Newton's few cryptic remarks did not reveal anything important about calculus.. So the assumption is E which says that neither Newton nor Leibniz learned from third sources.

What is the source of this question?

reply2spg wrote:What is the source of this question?

This question is from Powerscore Critical Reasoning Bible.

Komal can you please explain the why option (D) is not correct by negating the same.
I am a bit confused with the negation technique discussed in the CR Bible.

Thanks,
Sumit

komal wrote:Here's the OE

Answer choice (A): The argument is about the independent discovery of calculus; the author makes no assumption that Leibniz did not tell anyone else, and indeed the fact that Newton did tell Leibniz is not accepted by the author as undermining the conclusion.

Answer choice (B): Negate the answer: "A third person independently discovered calculus prior to Newton and Leibniz." Would this negated answer attack the argument? No, the author would just assert that three different parties independently discovered calculus.

Answer choice (C): The author cites Newton's letter as evidence that Newton felt he had disclosed ideas to Leibniz prior to Leibniz's publication date. No assumption is made that Newton felt that what was disclosed allowed Leibniz to learn something important. If you are uncertain of this answer, negate the choice to see if it weakens the argument.

Answer choice (D): This is clearly not an assumption of the argument because the author discusses Newton's letter to Leibniz prior to Leibniz's publication date.

Answer choice (E): This is the correct answer. The answer can be difficult because it is somewhat similar to answer choice (B), which many people already eliminated by the time they reached this answer. Answer (E) is different from answer (B) because it involves learning details from a third source. This is important because the conclusion references the independent discovery of calculus, and so the author must believe that neither Newton nor Leibniz learned anything substantial about calculus from other sources.

Answer E seems to be logical one out of other answer choices