Theodore Roethke’s poem “In a Dark Time” opens with an assertion: Hardships clarify who we are and what matters to us most. Without challenges to illuminate needs from wants, we risk taking aspects of our lives for granted. The Pulitzer Prize winner, who lost his father at age 14, understood the necessary alliance between darkness and light. As the poem continues, images are invoked of birds and insects, forests and caves, and the wind and the moon. Roethke believed his lifelong pull toward nature came from his father, who had owned and operated a 25-acre greenhouse in Michigan. “In a Dark Time” was included in Roethke’s posthumous 1964 book “The Far Field,” which won him his second National Book Award for Poetry.