Understand the Trinity The Trinity is one of the most important doctrines in Christianity—one of the key doctrines that separates Christianity from other religions. This classic pamphlet, also available as a chart, explains that Christians believe in One God in Three Persons—not three gods and not one God with three personalities. Pamphlet fits perfectly in most Bibles. Size is 8.5" x 5.5" folded and unfolds to 33" long.