Tom is undeniably the central character of the novel that bears his name. He is of absolute importance to the major plot; he is the embodiment of the struggle that carries the major theme (the impact of slavery on human morality — or, to state it in more universal terms, the problem of evil as it threatens the human spirit). Tom is not a developing character in the usual sense — he experiences hope and joy, pain and despair, but he does not really change. He is in no way a better or a wiser or a different person at the end of the novel than he is at the beginning. Yet Tom is real and believable, and above all he is not the "Uncle Tom" of the twenty-first-century dictionary definition, the "elderly slave" who behaves "fawningly" towards whites.
Tom is described, early in the book, as a physically powerful man, very dark-skinned, with African features. We can calculate his age approximately: He is eight years older than Shelby, both he and Shelby are the fathers of sons in their early teens; thus he must be, when the book opens, somewhere in his middle 40s — still in the prime of life. Although some of Stowe's African-American characters are of racially mixed ancestry — almost always, it seems, for a specific reason related to plot or theme — Tom, although apparently born in the United States, is said to be "truly African," and this is also for a reason: Stowe believed that specific psychological characteristics were peculiar to people of different races or ethnicities — for example, that Italians were volatile and excitable, "Anglo-Saxons" aggressive and adventurous, "Irishmen" (and women) overly sentimental and quick to anger or tears. She believed that members of the "African race" were more gentle, more loving and devoted to family (and thus potentially better Christians) than whites, especially those she called "Anglo-Saxons." Thus we feel that she intended Tom's unmixed African blood to show these traits in his character. Her narrator also says of Tom, several times, that he is "childlike" and "simple"; she does not mean that he is intellectually slow, but that he is what we would call entirely focused, unburdened by complexities of motive or doubt, confident (Stowe would say) of the goodness of God.
In order to understand this simplicity and confidence in Tom's character, it is necessary to understand something of the Christianity in which Stowe herself was so firmly rooted. Traditional Calvinism, the religion of Stowe's childhood, holds that the "elect" — those whom God has chosen to be saved — can do nothing of their own will to change their chosen status, nor can those who are not among the elect do anything to change their situation. A person's actions show in which group he or she belongs. Stowe apparently did not subscribe completely to this theory; the "election" of many of her characters (Augustine St. Clare, for example) appears to be up for grabs, something to be settled, if not by the person's own good or evil deeds, then at least by prayer while the person is still alive. But Tom himself is obviously among the elect; this is shown by his bearing and his spiritual power for good upon others as well as by his own confidence and in the specific signs of grace that he receives — for example, the vision of Christ he experiences when tempted to despair on Legree's plantation. His election makes Tom a very strong character, but it also ensures that he will not change, as people like Cassy, St. Clare, even Legree change when Tom touches them.
Finally, it is important to recognize that Tom's passivity is not a character flaw, not a failure to act when he ought to act, but really a kind of action, a species of resistance and of what our century would call "existential choice." With each of his masters, from Shelby to Legree, Tom is pitted against materialism, which is the basis of slavery. Even in its most benign form, as manifested in St. Clare, this materialism denies the spiritual, denies human love, turns every human connection or virtue into something to be used for profit — the "making" of money (which is not really made but is extracted from the bodies and souls of those who are turned into things for this purpose).
Stowe's original subtitle for Uncle Tom's Cabin was "The Man Who was a Thing"; she meant it ironically, of course, because Tom refuses to be made a "thing." His inaction is this refusal; his passivity is love — not liking, for he does not like Legree and does not pretend to; not admiration or attraction, for Tom like the rest of us cannot freely give or withhold these things; but love in the sense that the New Testament defines it: "Love bears all things, believes all things, hopes all things, endures all things" (see I Corinthians, 13: 1–13). Love is the recognition of the human spirit in one human being by another human being; it is the antithesis of materialism and of slavery. Tom's courage, his strength, and his heroism are all based in the Christian love — the good — that he freely chooses (as, he believes, God freely chooses him) throughout the book.