Carolyn E. De Latte, "Soulé, Pierre," American National Biography Online, February 2000, http://www.anb.org/articles/04/04-00932.html.
By experience and temperament, Soulé was unsuited to the world of politics and diplomacy. He cut his political teeth on revolutionary movements in France, and he continued to think and speak in terms of principle and of his perception of right and wrong. He readily supported those perceptions whether with a dueling pistol in his private life or with recommendations for war against Spain or the antislavery North in his public life. Tact was simply beyond his purview.