Shia Islam is a major branch of Islam whose traditions give a distinctive place to Ali ibn Abi Talib and the Prophet Muhammad’s family, the Ahl al-Bayt. Its central questions include who should guide the community after Muhammad and how that guidance shapes belief, worship and conduct.
Shia Muslims affirm one God, Muhammad’s prophethood, the Quran and accountability in the hereafter. They also differ among themselves. Twelver, Ismaili and Zaydi traditions have different histories and understandings of the Imamate. The account below explains those distinctions while giving particular attention to Twelver teachings.
Five principles in Twelver teaching
One established way of organizing Twelver doctrine is through five roots or principles of religion, usul al-din. Muhammad Shirazi’s Fundamentals of Islam presents them as follows:
- Tawhid: God is one, without a partner or equal. God alone is the Creator and the object of worship.
- Adl: divine justice. God does not act unjustly; justice belongs to the understanding of God’s relationship with creation.
- Nubuwwah: prophethood. God guides humanity through prophets, with Muhammad as the final prophet.
- Imamah: divinely appointed leadership and guidance after the Prophet.
- Maad: resurrection and return to God, with judgment and accountability beyond this life.
These principles concern what a believer understands about God, revelation and human destiny. They are a different kind of classification from a list of practical duties such as prayer and fasting.
Why Ali and the Imamate matter
Ali was Muhammad’s cousin and son-in-law. For Shia traditions, his position involves a claim to rightful leadership after the Prophet, rather than respect for an important relative alone.
In the Twelver theological treatise Al-Bab al-Hadi Ashar, the Imamate concerns religious and worldly guidance derived from the Prophet. Its argument connects the need for an Imam with protection against wrongdoing and preservation of religious teaching.
The treatise also defends the Imam’s immunity from sin and error, often called ismah. This is a theological claim about trustworthy human guidance. It does not make an Imam another god, and it should not be confused with saying every person who leads prayers is infallible.
The doctrine therefore reaches beyond the question of who held political office. It asks who has authority to interpret and embody the inherited religious message. An Imam can be central to that understanding even when he does not govern a state.
Who are the Twelve Imams?
Husayn Wahid Khorasani’s Principles of Faith gives the Twelver succession in this order:
- Ali ibn Abi Talib
- Hasan ibn Ali
- Husayn ibn Ali
- Ali ibn Husayn, Zayn al-Abidin
- Muhammad al-Baqir
- Jafar al-Sadiq
- Musa al-Kazim
- Ali al-Rida
- Muhammad al-Jawad
- Ali al-Hadi
- Hasan al-Askari
- Muhammad al-Mahdi
The final figure has a distinctive place in Twelver belief: he is understood to remain alive in occultation, or concealment, and to return as the Mahdi.
The Institute of Ismaili Studies’ account of occultation distinguishes a lesser occultation, dated 874–941, from the greater occultation beginning in 941. In the traditional account, designated agents represented the Imam during the first period; there is no equivalent special agent in the second.
This explains why the twelfth Imam’s absence is not understood by Twelver believers as the end of the Imamate. It also helps explain the importance of questions about scholarly authority during that absence.
Quran, hadith and the Prophet’s household
The Quran remains fundamental, while reports of the Prophet and teachings transmitted from the Imams help shape interpretation. Reverence for the Ahl al-Bayt connects the understanding of religious authority with the Prophet’s family.
A useful example is the report of the two weighty things, Hadith al-Thaqalayn. A version preserved in the Sunni collection Sahih Muslim 2408a urges adherence to the Book of God and reminds listeners of their duties toward Muhammad’s household.
The presence of this report in a Sunni collection illustrates shared material across traditions. Its interpretation, the authority attributed to the household and the understanding of succession remain matters of disagreement. Simply citing the report does not erase those differences.
Belief, reasoning and following a jurist
In Ali al-Sistani’s Islamic Laws, ruling 1, belief in the fundamentals should rest on personal insight grounded in reason. The text distinguishes this from following a qualified jurist in practical religious law, known as taqlid.
A jurist capable of deriving rulings is a mujtahid; a recognized authority followed for such rulings is a marja. Consulting a scholar about a practical duty is therefore different from treating the scholar as one of the Twelve Imams.
Daily worship also remains central. Sistani’s account of obligatory daily prayers lists five: morning, midday, afternoon, sunset and evening prayers. Distinctive doctrines about leadership do not replace worship directed to God.
Karbala, Ashura and Arbaeen
Husayn, Muhammad’s grandson and the third Imam in Twelver belief, was killed at Karbala in 680. Ashura, the tenth of Muharram, commemorates that death. The Harvard Islamic Studies program also documents how Karbala inspired art, poetry and storytelling, including illustrated screens used to narrate the events.
Arbaeen marks the fortieth-day commemoration and is associated with pilgrimage to Karbala. Remembering Husayn gives religious expression to grief, loyalty and reflection on resistance to injustice.
In his guidelines for Arbaeen pilgrims, Sistani connects remembrance with timely prayer, sincerity, self-reform and selflessness. This provides a concrete example of how a religious authority links pilgrimage to everyday ethical responsibilities.
Mourning should not be reduced to a single dramatic image or bodily practice. Narration, listening, prayer, artistic expression and pilgrimage offer different ways of understanding the place of remembrance in religious life.
Shia Islam extends beyond Twelver belief
The Ismaili Imamat’s own account describes a continuing hereditary line of Imams. It records Prince Rahim Aga Khan V’s designation as the fiftieth Imam in February 2025. This is the living Imamate of the Nizari Ismaili community, distinct from the Twelver understanding of a concealed twelfth Imam.
Zaydism has another history. Wilferd Madelung’s study published by the Institute of Ismaili Studies traces it to the movement surrounding Zayd ibn Ali’s revolt in 740. It should not be described as merely the Twelver list with a few names removed.
These differences make it essential to identify the community when discussing doctrine or authority. A Twelver manual, a Nizari institutional statement and a study of Zaydism illuminate different parts of the broader Shia landscape.
Conclusion
Shia Islam combines shared Islamic commitments with distinctive teachings about the Prophet’s family and rightful religious guidance. In Twelver belief, the five principles, the Twelve Imams and the occultation explain how theology and authority fit together.
Prayer, reasoning about belief and remembrance of Karbala show how those commitments enter religious life. Understanding Ismaili and Zaydi differences alongside Twelver teachings gives a fuller picture than presenting all Shia Muslims as followers of one identical institutional or political model.
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