This paper aims at probing into three achievements in Isaac Newton’s public life and three dark truths in his private life in Arthur Ziffer and Herbert Hauptman’s Isaac and Amanda. The first achievement as a physicist revealed in Newton’s dispute with Robert Hooke is that he developed the inverse square law and the laws of motion. The second achievement as a mathematician revealed in his dispute with Gottfried Wilhelm Leibniz is that he first developed calculus. The third achievement as a warden of the Royal Mint is that he prosecuted and executed dozens of counterfeiters including William Chaloner. On the other hand, the first dark truth in Newton’s private life is that he remained single for life because of his childhood trauma caused by his mother’s remarriage and her abandonment of him. The second dark truth is that he was reluctant to disclose his belief in Arianism. The third dark truth is that he suffered from a nervous breakdown or depression resulted from his implicitly expressed homosexual relationship with Nicolas Fatio de Duillier. Therefore, the play deserves critical attention in that it dramatizes Newton’s public and private life in a balanced way and induces us to survey his life on the whole.