Passage Summary: A historian argues that two famous thinkers, Leibniz and Newton, both invented calculus independently. Even though Newton had notes on it earlier and sent Leibniz a letter, the letter didn't actually explain the math, so Leibniz couldn't have stolen the idea from that specific letter.

Conclusion: Leibniz and Newton each came up with the ideas of calculus on their own without copying from one another.

Reasoning: While Newton had the ideas first and wrote a letter to Leibniz, that letter was too vague to explain calculus, and Leibniz published his work before Newton did.

Analysis: The historian is trying to prove a negative: that Leibniz didn't get the idea from Newton. The argument successfully rules out the letter as a source of information, but it leaves a massive gap regarding other potential sources. For the conclusion to hold, we must assume there were no other ways Leibniz could have seen Newton's work. Look for an answer that bridges this gap by stating Leibniz had no other access to Newton's private notebooks or unpublished thoughts.