Shiites and Sunnis share belief in the one God (Allah) who created the world. Likewise, while both agree on general characteristics of God (such as ever-living, omnipotent, merciful), there are also disagreements within both communities about the exact nature of these attributes. At the Day of Judgment humans will be resurrected, judged, and condemned or rewarded in Hell or Paradise. During human history, God has sent a number of prophets and revealed the truth. Both Sunnis and Shiites also believe in the existence of a satan-like character (Iblis), in angels, and in jinns (demons). Distinctly Shiite elements within this general framework include the Imams, the pivotal role of the Mahdi, and more pronounced rationalist and Neoplatonic tendencies in theological debates.
One of the most characteristic features of Shiism is the belief in the Imams. The Imams are sometimes attributed with superhuman powers such as speaking all languages (including those of animals) and having knowledge of the future. Sunni polemicists often criticize Shiites for their deification or exaggerated veneration of the Imams, which the critics identify with the alleged tendency of Jews and Christians to ignore the difference between the creator and the created world.
Another common, though not universal, feature of the Shiite concept of the Imams is that the final Imam, the Mahdi, who is currently in Occultation (for Twelver Shiites, this is the twelfth Imam), will return as the apocalyptic savior. In a well-known hadith, Muhammad announced that "Day and night will not end before God has sent a man forth from my house who bears the same name as I. He will fill the world with justice and equity just as it was filled with oppression and tyranny before" (Shi'ism, by Heinz Halm, 36).
Shiite religious thought has a marked rationalist tendency. An early representative of this trend was the Shaykh al-Mufid (949-1022) in the Buyid period. Another crucial stage took place in al-Hilla, the center of Shiite learning during the Mongol period. It is best known for the Allama al-Hilli (1250-1325; lit. 'the most learned man from al-Hilla'), a rationalist theologian and legal scholar who had embraced tendencies of Mutazilism, a school of rationalist theology which emerged in 9th-century Baghdad, but died out in Sunni Islam. The Allama al-Hilli became very influential in Safavid Iran. His exposition of Shiite dogma, The Eleventh Chapter, still enjoys authoritative status. Shiite thought in the pre-modern era often has Neoplatonic features, in particular the idea of emanations that bridge the gap between the transcendent God and the contingent created world. These also constitute a popular trend in Shiite esoteric exegesis of the Quran. The beginning of the process of creation is thus sometimes described as a manifestation of the divine light. In such traditions, this overflowing light comprises the essences of the protagonists of Shiite salvation history.
The so-called theosophical school of Isfahan with its best known representative Mulla Sadra (c. 1571-1641) is but one example of the popular mystical tradition in Shiite Islam. Sufi orders had been popular in Iran, but were persecuted under the Safavids. Mysticism survived, however, in this intellectual form as well as in the poetic tradition. Thus, even the Iranian revolutionary leader Khomeini, who is mostly associated in the West with his rigorous imposition of conservative Islamic principles and a stern-looking image, has left behind a collection of mystical poetry.