Birney’s desire to obtain justice for Indians and slaves was certainly admirable; an early biography of Birney (by an abolitionist who knew him) stated that his pro‐​Indian beliefs came first in time, and that this concern then precipitated his concern for slaves. This seems an oversimplification, however. To say that Birney’s interest in Indians preceded his interest in antislavery does not mean that the former caused the latter. In fact, Birney had been interested in arguments against slavery for a long time. His mother seemed mildly antislavery, given that she insisted on paying wages to slaves who had been given to her as gifts; and his father, though a slave owner, did not discourage his son from learning about antislavery arguments. Moreover, during his time at Princeton, Birney heard a good deal of antislavery rhetoric from both professors and fellow students. If anything prevented Birney from openly embracing antislavery views at this time, it was probably public pressure that would have interfered with his pursuit of the good life in Kentucky. Yet, after Birney moved from Kentucky to Huntsville, Alabama, to establish a plantation of his own, he purchased additional slaves to do the field work with no apparent damage to his conscience.

If there was a common element in Birney’s interest in moral reform, it was undoubtedly his religious conversion to a type of Presbyterianism that was infused with the revivalist spirit begun in upstate New York by Charles Finney and other evangelical preachers. According to Birney’s new religious convictions, even the individual could bring about significant moral reform, so it was not necessary to wait on the actions of a state legislature to abolish slavery, or at least to mitigate its harmful effects. It was during the summer of 1826, shortly after his conversion, that Finney happened to read the African Repository and Colonial Journal, published by the American Colonization Society. Here he found his first plan to direct his considerable energy to the antislavery crusade.

The American Colonization Society recommended the voluntary emigration of free blacks, including former slaves, to Liberia, West Africa. Colonization societies had been around for a long time. They were popular even in the South, where they were often supported by prominent proslavery advocates. This raised the suspicion of antislavery types, who suspected that plans for colonization served the interests of racists who wanted to diminish the number of blacks in America. But when Birney later published a repudiation of colonization, he stressed that the founders of the American Colonization Society sincerely believed that voluntary emigration would hasten the end of slavery in America. He also noted, however, that the stress on voluntary emigration was misleading at best. Free blacks in Alabama were legally forbidden to associate with slaves, and most whites wanted nothing to do with them. Schools for black children were legally forbidden, and this, along with other legal measures, made it questionable whether those blacks who volunteered to be shipped to Africa were acting without compulsion. Moreover, some slaveholders offered to free their slaves only on the condition that they agreed to move to Africa, and this poked another hole in the argument that colonization was purely voluntary.

In Letter on Colonization (1834), which was published as an open letter to Rev. Thornton J. Mills, Corresponding Secretary of the Kentucky Colonization Society, Birney explained why he could no longer support voluntary efforts to send free blacks (including newly emancipated slaves) to Liberia, where they could form their own society free of racial prejudice. During his time as vice‐​president of the Kentucky Colonization Society, Birney had worked energetically to raise funds and generate public support for colonization; and his efforts contributed to shipping 150 volunteers from New Orleans to Liberia. Colonization, however, necessarily entailed gradualism as an emancipation strategy, and Birney became convinced that gradualism was largely a rationale for current slave owners to claim that they opposed slavery without doing anything concrete to end it.