Scholars and researchers have expressed different views concerning the birth of Shi'ism and its first appearance. Others too have attempted to evaluate it, approaching it from the point of view of their respective ideological and intellectual predispositions.
Some people believe that Shi'ism arose after the death of the Messenger of God, peace and blessings be upon him and his family, and that its defining essence took shape when his Companions set about selecting his successor. Thus the historian al-Ya'qubi writes:
"A number of the Migrants and the Helpers refused to swear allegiance to Abu Bakr, inclined as they were to favor 'Ali b. Abi Talib, peace be upon him! al-'Abbas b. 'Abd al-Muttalib, al-Fadl b. al-'Abbas, al-Zubayr, Khalid b. Sa'id, al-Miqdad, Salman, Abu Dharr, 'Ammar, al-Bara'a, Ubayy b. Ka'b were part of this group." 
al-Mas'udi, also a famous historian, writes:
"Salman al-Farisi was a Shi'i from the very outset, and 'Ammar b. Yasir was known as a Shi'i throughout his life. When 'Uthman was elected to the caliphate, he remarked: 'It is not the first time you have denied the caliphate to the one deserving it!' Abu Dharr was similarly an outstanding proponent of Shi'ism." 
Another group of scholars place the emergence of Shi'ism during the caliphate of 'Ali b. Abi Talib, peace be upon him, while others suggest that it began to take root towards the end of the caliphate of 'Uthman. Still others regard Imam al-Sadiq, peace be upon him, as the founder of Sh i'ism. Some people again imagine Shi'ism to be the result of a wish for revenge nurtured by the Iranians, so that its origins may be considered essentially political.
Then there are those who see in Shi'ism a contingent phenomenon in Islamic society and history, without any strong presence or substance. They imagine it to have gradually expanded in Islamic society as the result of certain social and political developments at a relatively advanced point in Islamic history, There are even those who assert this segment of the Islamic ummah to be the brainchild of an imaginary personality by the name of 'Abdullah b. Saba', basing on this assumption all their judgements concerning Shi'ism and concluding that Shi'ism is nothing more than an anomaly. 
Theories such as this amount to nothing more than obstinate calumnies, perpetrated to conceal the truth; or at the very best they spring from complete ignorance of the true culture of Shi'ism and its rich heritage.
Dr. Taha Husayn, a well-known Egyptian and therefore Sunni scholar, writes:
"The fact that the historians make no mention of Ibn al-Sawda' i.e., 'Abdullah b. Saba' being present at the battle of Siffin together with his followers proves at the very least that the whole notion of a group of people led by him is a baseless fabrication. It is one of those inventions that acquired currency when the conflict between the Shi'is and other Islamic groups intensified. In order to underline their hostility, the enemies of the Shi'ah tried to insert a Jewish element into the origins of their sect. If the story of 'Abdullah b. Saba' had any basis in historical fact, his cunning and guile could not have failed to show itself at the battle of Siffin.
"I can think of only one reason for his name not occurring in connection with that battle: that he was an entirely fictitious person, dreamed up by the enemies of the Shi'ah in order to vilify them." 
Similarly, Dr. 'Ali al-Wardi, professor of history at Baghdad University, writes:
"Did Ibn Saba' actually exist or was he an imaginary personality? For those who wish to study the social history of Islam and draw the appropriate conclusions, this is an extremely important question. It is claimed that Ibn Saba' incited unrest, but no such person ever existed. The whole story is reminiscent of the claim made by the Quraysh at the beginning of the Prophet's mission, peace and blessings be upon him and his family, that he received his teachings from a Christian slave by the name of Jabr and based his preaching on the instruction he received from him." 
Muhammad Kurd 'Ali, another Sunni scholar, writes:
"Some of the well-known Companions who at the dawn of Islam followed 'Ali, peace be upon him, became known as the Shi'ah. What can be deduced from the written sources is that certain shortsighted people regarded Shi'ism as a collection of innovations and fabrications stitched together by a person known Abdullah b. Saba' or Ibn al-Sawda'. However, there can be no doubt that this view of things is pure superstition and fantasy, for this Abdullah b. Saba' the Jew exists only in the world of the imagination. Any attempt to link the origins of Shi'ism to him must be regarded as a sign of pure ignorance." 
In contrast to all the opinions reviewed so far, one group of scholars believe Shi'ism to have been first expounded by none other than the Prophet himself, peace and blessings be upon him and his family, and that it was established in conformity with his command.
Hasan b. Musa al-Nawbakhti and Sa'd b. Abdullah write:
"The party of 'Ali b. Abi Talib, peace be upon him, was the first to emerge in the time of the Prophet, peace and blessings be upon him and his family, and it became known as the Shi'ah (partisans) of 'Ali. It was known that they favored , 'Ali for the leadership of the community and that they were his devoted companions. al-Miqdad, Salman, Abu Dharr and 'Ammar belonged to this group, and they were the first to be called Shi'i. Use of the word Shi'ah was not new; it had been applied in the past to the followers of some prophets such as Nuh, Ibrahim, Musa, and 'Isa." 
This view is confirmed by numerous Shi'i scholars, and there are many traditions to the effect that the Prophet, peace and blessings be upon him and his family, applied the name Shi'ah to the companions and followers of 'Ali, peace be upon him.
When discussing the occasion for the revelation of this verse, "Certainly those who believe in the One God and who do good deeds are in truth the best people in the world." (98:7), Sunni exegetes (mufassirin) and traditionists (muhaddithin) report Jabir b. 'Abdullah to have said: "One day I came to the presence of the Prophet, peace and blessings be upon him and his family, 'Ali entered the room, causing the Prophet to remark, 'My brother has come. I swear by God that this man and his shi'ah (supporters) will be among the saved on the Day of Resurrection.'" 
al-Tabari, the well-known Sunni exegete and historian, also remarks in connection with the same verse that the Prophet used the word shi'ah when referring to the supporters of 'Ali.
There is then prophetic authority for designating the followers of 'Ali, those who were particularly devoted to him, as Shi'ah.
We thus see that the word Shi'ah is essentially coterminous with Islam itself, for the Prophet himself used it If we sometimes use the designation Ja'fari Sh i'ism, this is on account of the exertions made by Imam Ja'far al-Sadiq to disseminate the culture of Islam and Sh i'ism. The struggles for power that were taking place in his lifetime afforded him a suitable opportunity to confront the political conditions of his environment. The various ideas that were gaining currency and the foreign elements such as analogical reasoning and preference that had entered Islamic jurisprudence caused him to embark on a program of teaching and reform.
Muhammad Fikri Abu 'l-Nasr, a well-known Egyptian Sunni author, has the following to say with respect to the essence of Shi'ism:
"In its theological principles, Shi'ism has nothing to do with Abu 'l-Hasan al-Ash'ari, and in its detailed legal provisions nothing to do with any of the four Sunni schools of law. For the school established by the Imams of the Shi'ah is more ancient, and therefore more reliable and more deserving to be followed than the other schools. All Muslims followed their school for the first three centuries of Islam. The Shi'ah school of law is also more worth following because in it the gate of independent reasoning (ijtihad) will remain open until resurrection, and because its formation was totally uninfluenced by political factors and struggles." 
Abu 'l-Wafa' al-Ghunaymi al-Taftazani, another Sunni scholar, says the following:
"Numerous researchers of the past and the present, in both the East and the West, have expressed erroneous views concerning Shi'ism. People then unquestioningly repeat these views, without adducing the slightest evidence or proof. One of the reasons that has led to Shi'ism being thus unjustly treated is that those who originate and spread such views are unacquainted with the books of the Shi'ah themselves and rely exclusively on the writings of their enemies. Western imperialism has also played a role in this regard by constantly attempting to sow dissension among Shi'is and Sunnis and propagating unfair and controversial theses in the name of unfettered academic research." 
These remarks permit us to grasp well the depth of the distortion that has taken place, the extent of deviation from the truth, as well as the mentality of those who have been inspired by their own impure motives or influenced by political factors. Instead of giving primacy to the interests of the Qur'an, Islam and the unifying qiblah of all Muslims, they compete with each other in sowing dissension and causing disunity; Islam itself is sacrificed to their goals, and the common enemy of all Muslims profits.
It is essential to add the following point, that the designation Shi'ah in the time of the Prophet, peace and blessings be upon him and his family, did not apply to a group that was seeking to detach itself from the rest of the Muslims. It is simply that a certain number of Muslims in the time of the Prophet considered 'Ali, peace be upon him, superior to all others in his knowledge of the truths of Islam and the values and aims of the Prophet's mission. They were profoundly attached to him on account of his lofty insight and vision, his link to the source of all perfection, and, in short, all his moral and spiritual qualities. He inspired them as a perfect specimen of humanity worthy of their imitation.
It is of course true that the Shi'ah first appeared on the scene as a distinct group after the death of the Most Noble Prophet, peace and blessings be upon him and his family, when the close companions of 'Ali, peace be upon him, refused in the wake of the meeting at the Saqifah to swear allegiance to Abu Bakr and proclaimed themselves as a party among the Muslims dedicated to defending the clear and unambiguous texts providing for the entrusting of rule over the Muslims to 'Ali.  Rejecting the attempt made at the Saqifah to neutralize his claim and the recourse that was had to the thesis of "the welfare of the Muslims," they separated themselves from the majority and formed a group devoted to him.
In this group were to be found such outstanding Companions as Ammar, Abu Dharr, al-Miqdad, Salman and Ibn 'Abbas, whose sincerity, devotion and commitment had been praised by the Prophet Thus he said of Ammar and his parents:
He also proclaimed the kindness and favor God had shown to four great personages: "God has enjoined on me the love of four people, and informed me that He himself loves them." When asked who they were, he replied: "'Ali (repeating the name three times), Abu Dharr, Salman, and al-Miqdad." 
He spoke as follows of the sincerity and piety of Abu Dharr: "The blue sky has not sheltered, nor has the earth borne, one more honest than Abu Dharr; he lives upon earth with the same ascetic detachment as 'Isa the son of Maryam." 
Referring to the station in the hereafter of three persons, he said: "Paradise longs for three persons: 'Ali, Yasir, and Salman." 
The Prophet supplicated for Ibn Abbas as follows: "O God, teach him the science of interpreting the Qur'an, make him erudite in all things religious, and establish him as a believer." 
These then were the devoted followers of 'Ali, peace be upon him, men convinced that he should have been the immediate successor of the Messenger of God, peace and blessings be upon him and his family, and that the caliphate was his indubitable right.
That which was a matter of dispute and disagreement after the death of the Prophet was the question of succession to the political leadership, not the Imamate, which included the spiritual dimension of the Prophet's legacy. No one at the Saqifah had anything to say about choosing an Imam, and the question was not even raised. Was this because nobody had the least doubt concerning 'Ali's supremacy in spiritual matters, or was it that because none of the claimants to the caliphate and the succession was qualified for the Imamate no one laid claim to it? The truth of the matter is unclear.
For some time then there was no mention of the Imamate. But after the death of several of the caliphs, the question gradually came to the fore, and some of the caliphs, like Mu'awiyah, for all his lack of commitment to Islam, began calling themselves Imams.
The topic discussed in works of theology is the Imam and the Imamate, while the terms used in books of history and the oral and written statements of Sunni scholars are caliph and caliphate. 'Ali and his descendants, recognized as the leaders of the Shi'ah are however consistently referred to as Imams. This reflects the Shi'i belief that strict and precise adherence to the criteria of religion, unswerving piety, and a whole series of other special qualities, must be present in the person of the Imam.
One of the pupils of Imam Ja'far al-Sadiq, peace be upon him, Hisham b. Hakam, wrote a book on the subject of the Imamate in which he set forth its theoretical bases. 
In addition to the office of prophethood, which comprised the responsibility for receiving and conveying revelation to mankind, the Prophet was the ruler of the Muslims, empowered over all their affairs. From the moment on that the Muslims established a collective existence, all the societal affairs of the people were regulated by the Prophet: the appointment of governors, commanders, and judges; the distribution of booty; the issuance of orders for war and so on. He implemented divine commands and ordinances in accordance with the ruling function that was vested in him, and it was the duty of the people to obey his commands and instructions.
Rulership, the administration of society, and the establishment of public order and security were thus part of his prophetic function; prophethood and spiritual leadership on the one hand and leadership and rule on the other were both combined in a single divinely chosen person.
The dispute that occurred after his death related only to leadership and rule, so that those people who aspired to the position of rule after the Prophet never advanced any claim of special communication with God or the receipt of revelation, nor did they present themselves as spiritual leaders or guides. Their whole ideal was to seize the reins of power and administer the affairs of the Muslims, paying attention only to the need of preserving the unified society of Islam from disorder and discord by means of careful strategy and plan.
When the people swore allegiance to Abu Bakr after the death of the Prophet, peace and blessings be upon him and his family, Abu 'Ubaydah proposed to 'Ali, peace be upon him: "Abandon this matter to Abu Bakr. If you survive him, you are worthier of the office of caliph than anyone else, for none can doubt your abundant faith, virtue, and intelligence. Furthermore, you preceded others in your profession of Islam, and you enjoy the additional advantage of being related to the Messenger of God by blood and by marriage." 'Ali replied:
"O Migrants! I entreat you by God not to remove governance from the Household of the Prophet, and to establish it in your house; do not deprive the People of Muhammad's House of their station and office." 
 al-Ya'qubi, al-Tarikh,
Vol. II, p. 114.
 al-Mas'udi, Murujal-Dhahab.
 For more details concerning this
mythical personality, see Murtada al-'Askari, 'Abdullah bin Saba'.
 Taha Husayn, al-Fitnat al-Kubra,
Vol. II, p.90.
 Cited in Dr. Haykal, Hayat
Muhammad, p. 136.
 Kurd 'Ali, Khitat al-Sham,
Vol. VI, p. 246.
 al-Nawbakhti, al-Maqalat wa
al-Firaq, p. 15.
 Ibn Hajar, al-Sawa'iq,
Chapter I; al-Khwarazmi, al-Manaqib, p. 66; al-Hamawini, Fara'id
al-simtayn, Vol. I, Chapter 13; al-Qunduzi, Yanabi' al-Mawaddah,
Chapter 56; Ibn al-Sabbagh, Fusul al-Muhimmah, p. 105; al-Ganji,
Kifayat al-Talib, p. 118.
 Cited in al-Muraja'at,
 al-Radawi, Ma'a Rijal al-Fikr
fi al-Qahirah, pp. 40-41.
 al-Tabari, Tarikh, Vol.
 al-Hakim, al-Mustadrak,
Vol. III, p. 383.
 al-Tirmidh i, Jami' al-Sahih,
Vol. V, p. 233.
 Ibn Majah, al-Sunan, Vol.
I, p. 53.
 al-Tirmidhi, Jami' al-Sahih,
Vol. V, p. 334.
 al-Tirmidhi, Jami' al-Sahih,
Vol. V, p. 332.
 al-Hakim, al-Mustadrak,
Vol. III, p. 536.
 Ibn Nadim, al-Fihrist,
 Ibn Qutaybah, al-Imamah wa al-Siyasah, Vol. I, p. 12.