/ˈdɒnəˌtɪzəm/
Named after Donatus Magnus, a 4th-century bishop of Carthage who was a leader of the movement. It arose in North Africa as a response to Christians who had compromised their faith during the Diocletianic persecution.
Donatism was a schismatic movement that held that the Church must be a church of "saints," not "sinners," and that sacraments, such as baptism, administered by traditores—bishops who had surrendered the Scriptures to the authorities during persecution—were invalid. The core error of Donatism is tying the efficacy of a sacrament to the moral purity or spiritual state of the minister administering it. The orthodox Christian position, championed by Augustine of Hippo, is that the validity of a sacrament comes from Christ himself (ex opere operato), not from the holiness of the human agent.
The term "Donatism" is not present in Webster's 1828 dictionary. The entry for Schism is relevant: "A division or separation in a church or denomination of christians, occasioned by diversity of opinions."
Modern Donatism manifests in a self-righteous, separatist spirit that judges the validity of other churches or ministries based on perceived moral or doctrinal failings of their leaders. It is the attitude that says, "We are the true, pure church, and that pastor's ministry is invalid because of his past sins or current imperfections." This leads to endless church splits, an uncharitable view of fellow believers, and a misplaced focus on human worthiness rather than on Christ, who is the true officiant and guarantor of His ordinances.