" Eisenhower defined the ability to nurture optimism and elicit cooperation as the essence of leadership. He believed that such ability was not an innate but an acquired characteristic, the acquisition of which resulted from serious psychological study. “The one quality that can be developed by studious reflection and practice is the leadership of men,” he wrote to his son in 1943. "

― Walter Isaacson , Profiles in Leadership: Historians on the Elusive Quality of Greatness