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
Neither Newton nor Leibniz learned crucial details about calculus from some third source.