The very definitions of slave and human are incompatible. If you are a human, then you are the same as every other human in terms of your basic biology. To be owned by anyone else as a slave denies this basic equality, and because of this you would be denied every other equality as well. In specific terms, slaves could not legally marry, even though they did informally. Nor could they keep control of their children, who were immediately property of the master. Father, mother and/or child could be sold and separated at will.
Abolitionists fought in both passive and active ways against slavery. Passive, in terms of working more slowly or sabotaging tools, and working out signing codes to let other slaves know when the master was or wasn't around.
Others were more active, and actually helped slaves along the Underground Railroad, escaped themselves, or later joined the Union Army to fight against the Confederacy, sometimes liberating their own families through force of arms.
The stain of slavery proved to be a contradictory moment in the history of the United States. In a nation predicated upon "justice for all," "inalienable rights such as life, liberty, and the pursuit of happiness," and a nation whose primary function was to "secure the blessings of liberty to ourselves," slavery presented much in the way of opposition. The slave trade was inhumane, as individuals were taken from homes in Africa, bought for commodities such as sugar and tobacco, and used for inhumane labor, kept and resold for personal gain. Slaves were packed into vessels and conditions such as the Middle Passage, which attempted to cram in as many slaves as possible in the smallest of spaces for the transatlantic journey. With the advent of the cotton gin and the increase in cotton production, more slaves were needed to pick cotton in greater quantities, generating more profit and more need for slaves. The entire Southern United States economy was predicated upon the forced servitude and the enslavement of other human beings.
Abolitionists saw this moral outrage and developed many ways to arouse the nation's conscience to such an overt violation of American principles. William Lloyd Garrison, an abolitionist from Massachusetts, published a newspaper called "The Liberator" and sought to create a venue where abolitionists could use their voice in speaking out against the atrocities of slavery. Frederick Douglass was an escaped slave who committed himself to the abolitionist movement through speeches and writings, in particular his own Autobiography with vivid examples of slavery's cruelty. Harriet Beecher Stowe used literature as her medium of abolition when she published her landmark against slavery, "Uncle Tom's Cabin." The novel highlighted the brutality of the slave culture and aroused much in the way of anger towards those who owned slaves. Other abolitionists were conductors on the Underground Railroad, a secret movement that sought to take slaves away from plantations and lead them to freedom. Harriet Tubman was seen as a Moses figure as she led thousands of slaves to freedom via the Underground Railroad. Levi Coffin was an Indiana Quaker who also served as a conductor and built a safe house for the Underground Railroad. In a more defiant manner, John Brown was an abolitionist who killed pro- slavery followers when both sides clashed in the Kansas- Nebraska territory. Brown and his sons also led a contingent of slaves and other followers to the federal arsenal at Harper's Ferry in Virginia. His hopes were to arm the slaves in Virginia so that they would rebel from their masters. Brown caused a great deal fear in Southeners in his belief that violence against slavey was justified, as evil must be destroyed with force at every possible turn.