Immanuel Kant
Kant published a second edition of the "Critique of Pure Reason" ("Kritik der reinen Vernunft") in 1787, heavily revising the first parts of the book. Most of his subsequent work focused on other areas of philosophy. He continued to develop his moral philosophy, notably in 1788's "Critique of Practical Reason" (known as the second "Critique") and 1797's "Metaphysics of Morals". The 1790 "Critique of Judgment" (the third "Critique") applied the Kantian system to aesthetics and teleology. It was in this critique where Kant wrote one of his most popular statements, ""it is absurd to hope that another Newton will arise in the future who will make comprehensible to us the production of a blade of grass according to natural laws"".
John Keats
When Keats died at 25, he had been writing poetry seriously for only about six years, from 1814 until the summer of 1820; and publishing for only four. In his lifetime, sales of Keats' three volumes of poetry probably amounted to only 200 copies. His first poem, the sonnet "O Solitude" appeared in "the Examiner" in May 1816, while his collection "Lamia, Isabella, The Eve of St. Agnes and other poems" was published in July 1820 before his last visit to Rome. The compression of his poetic apprenticeship and maturity into so short a time is just one remarkable aspect of Keats' work.