Complex sentence: Among other works, he wrote the introduction to Fredrick Douglass' second autobiography, "My Bondage and My Freedom" (1855), which constituted an important move away from seeking approval and authentication from white abolitionists in African-American accounts of slavery.
Split into simpler sentences: Among other works, he wrote the introduction to Douglass' second autobiography, "My Bondage and My Freedom" (1855). It expressed independence from seeking approval and authentication from white abolitionists in African-American accounts of slavery.