Sefer ha-Ikkarim

Sefer ha-Ikkarim ("Book of Principles") is a fifteenth century work by rabbi Joseph Albo, a student of Crescas. It is an eclectic, popular work, whose central task is the exposition of the principles of Judaism.

Agreeing with Simeon ben Jospeph of Lunel (ie: Duran), Albo held that there are three basic principles (ikkarim) that are necessary for the divine law to exist:
# the existence of G-d,
# the revelation of G-d,
# the reward and punishment of G-d.

From these three principles, Albo posited that there are eight derivative principles (shorashim):
# From the existence of G-d derives the principle of God's unity
# From the existence of G-d derives the principle of God's incorporeality
# From the existence of G-d derives the principle of God's timelessness
# From the existence of G-d derives the principle of God's perfection
# From the revelation of G-d derives the principle of G-d's omniscience
# From the revelation of G-d derives the principle of G-d's prophecy
# From the revelation of G-d derives the principle of the authentication of G-d's prophet
# From the reward and punishment of G-d derives the principle of individual providence.

The denial of these principles, no less than the denial of the first three, makes one a heretic ("kofer be-ikkar"). It is understood in Albo's work that there are three kinds of law: natural law, conventional law, and divine law. Natural law is the same for all persons, times, and places; conventional law is ordered by a wise judge in accord with reason; divine law is given by G-d through a prophet.