Stowe uses Uncle Tom to explore and symbolize the plight of the Black slave. Through him, Stowe attempts to depict slavery from a slave's point of view.
By having Tom literally sold down the river, Stowe is able to depict slavery in various manifestations, from the best to the worst of situations. Tom becomes a universal symbol of slavery and illustrates that even in the best of circumstances, slavery is an undesirable and precarious state.
The novel opens with Tom experiencing the best of lives for a slave, living with his wife and children in a snug cabin, overseen by a caring and compassionate mistress in the form of Mrs. Shelby. However, even this humble life, which the average white person would take for granted, is ripped away from Tom. He is sold south, despite the great grief it causes him and his family. He is shown to have no security because he does not own his own body.
The novel goes on to depict Tom in several different circumstances, such as in the household of the kind but careless Mr. St. Clare, owned by the selfish, childish, and petty Mrs. St. Clare, and then sold to the sociopathic Simon Legree. Through it all, Tom symbolizes the lack of agency and control even the worthiest of slaves has over his own life. In the end, the only choice he can make is to die rather than capitulate to Legree.