**QUESTION TEXT:** Historian: Leibniz, the seventeenth-century philosopher, published…

**QUESTION TYPE:**** **Necessary Assumption

**CONCLUSION:**** **Leibniz and Newton each independently discovered calculus.

**REASONING:**** **Newton had been working with calculus for a decade before Leibniz published his results. Meanwhile Newton could not have influenced Leibniz.

**ANALYSIS:**** **The argument is assuming that no one else discovered calculus and influenced both Leibniz and Newton.

___________

- If Leibniz had told his wife it wouldn’t really affect the argument.
- This could have happened if the third source did not influence Newton or Leibniz. (suppose the third person lived far away in China.)
- The argument makes no claims about what Newton believed.
- They could each have known yet still discovered calculus independently.
**CORRECT.**It’s hard to say they discovered it if some third source told them crucial details.

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Joseph Castro says

Hello:

Using your logic above, is B not as good (or even better) an answer as E?

Thanks!

TutorLucas (LSAT Hacks) says

The issue with (B) is that even if someone had discovered calculus before Leibniz and Newton, that wouldn’t rule out the possibility that they still both discovered it independently. Just because someone came up with calculus before them, doesn’t mean that they in any way influenced or were in contact with Leibniz or Newton.

(E), on the other hand,

doesrule out this possibility. The negation of (E) is that “Newton and Leibniz did learn crucial details about calculus from a third source”. That is fatal for the argument. How can we say they’ve independently discovered calculus if someone else gave them crucial details about it?