December 23, 1193: Thorlac Thorhallsson, Iceland's prominent bishop who insisted on clerical discipline and celibacy, abolished lay patronage, and fought simony, dies (see issue 63: Conversion of the Vikings).
December 23, 1569: Russian czar Ivan IV ("the Terrible") has Philip, bishop of Moscow, killed in his prison cell after the bishop criticized Ivan's policies and mass executions.
December 23, 1648: Robert Barclay, the most prominent theologian in the early Quaker church, is born in Gordonstoun, Scotland. His Apology for the True Christian Religion (1676) is considered the classic exposition of Quaker principles.
December 23, 1652: John Cotton, the most eminent minister in colonial Massachusetts and considered "the father of New England Congregationalism," dies. When he fell ill earlier that year, his followers observed a comet (or "attendant to the stars"), which "continued all that while and until his buryal . . . then disappeared" (see issue 41: American Puritans).