SA'ADJĀH ben JÓSĒPH. — Gaonite, born in Fajjūm in 882, died in 942. He was a grammarian, exegete, translator of the Bible into Arabic, theologian, polemicist, and founder of medieval Jewish religious philosophy. Until the age of 30, he lived in Egypt; then in Palestine, Syria, and Babylonia, where in 928 he was appointed head of the Talmudic Academy of Sūrā.
In 931, he completed his commentary on the *Sépher jésirāh*; in 933, his principal philosophical work: *Book of Beliefs and Religious Doctrines* (in Arabic: *Kitāb al-amānāt wa 'l-i'tiqādāt*; in Hebrew: *Sépher ha-'èmūnāth wē-ha-dē'ōth*). Even his biblical commentaries bear a philosophical tone. He opposed everywhere the Christian Trinitarian concept, Zoroastrian dualism, and Islamic theories contrary to biblical Revelation. A follower of *kalām* in its Mu'tazilite rationalistic aspect, he promoted the concept of God’s unity and human free will. Religious truth is that revealed to Israel; reason is the common foundation of the most varied religions, which derive from men rather than from God. Revelation has an educational purpose without annulling man’s rational activity, which seeks to demonstrate the truth of what God Himself revealed and preserved through historical tradition—tradition that arises from collective awareness, excluding illusion and error. What is historically true for all is indeed true.
The existence of the world presupposes the existence of the Creator, and creation is a form of Revelation. The world consists of parts subject to constant becoming and perishing. Accidents arise in the flow of time and are limited by time itself. The world is not eternal. Morality, willed by God, aims to make man happy (eudemonism). Theodicy presupposes the afterlife as an element of balance. Suffering is a means of purification and a path toward humility and eventual well-being. The resurrection presupposes the reunion of the soul with the body and will coincide with the time of messianic redemption.
In addition to the above, the following works by him should be noted: *‘Aghrōn*, a kind of Hebrew dictionary for poets, with a study of various forms of poetry; *The Books on Language*, the oldest grammar preserved to us; a commentary on the 70 *hapax legómena* of the Bible; and against the Karaites: *The Book of Refutation of ‘Anon* and *The Book of Distinction*.
Many of S.’s works were translated into Hebrew and various European languages.
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J. Gothmann, *Die Philosophie des Judentums*, Munich 1933, pp. 69–84 and passim;
M. Ventura, *La philosophie de S. Gaon*, Paris 1934;
G. Vajda, *Introduction à la Pensée juive du moyen âge*, ibid. 1947, ch. 2, pp. 219 ff.;
E. Gilson, *La philosophie au moyen age*, ibid. 1947, pp. 369 and 376.