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 or Leibniz knew that the other had developed a version of calculus prior to Leibniz's publication.