Heresy makes for progress.
It was not Christianity which freed the slave: Christianity accepted slavery; Christian ministers defended it; Christian merchants trafficked in human flesh and blood, and drew their profits from the unspeakable horrors of the middle passage. Christian slaveholders treated their slaves as they did the cattle in their fields: they worked them, scourged them, mated them , parted them, and sold them at will. Abolition came with the decline in religious belief, and largely through the efforts of those who were denounced as heretics.
Less power to religion, the greater power to knowledge