What two factors determine who is Sunni and Shiite?

Answer 1

all in all we can categorize these difference into two levels:one level lies in principles and other in interpreting of Quran .

first level:the five principles of religion as stated by shiism include:tawhid or belief in divine unity,nubuwwah or prophecy,maad or ressurrection,imamah or the immamate:belief in the imams as successors of the prophet and Adl or Divine justice.in the Three bsic principles -unity, prophecy and resurrection-Suunnism and shiism agree.it ts only in the other two that they differ. in the question of the imamate it is the insistence on the esoteric function of of the imam that distingushes the shiites perspective from the Sunni.in the question of Justice it is the emphasis placed upon this attribute as an intrinsic quality of the divine nature that is particular to shiism.we might say that in the esotericformulation of Sunni theology,especially as contained in Asharism there is an emphasis upon the will of god .whatever god will is just precisely because it is willed by God.and intelligence is in a sense subordinate to this will and to the voluntarism which characterizes this form of theology.in shiism however , the quality of justice is considered as innate to the Divine Nature..God can not act in n unjust manner because it is His nature to be just.Fa,him to be unjust would violate His own nature,which is impossible.intelligence can judge the justness and injustness of an act and this judgment is not completely suspended in favor of a pure voluntarism on the part of God.

second level:shiism also different in its consideration of the means whereby the original message of Quranic revelation reached the islamic community and thereby in certain aspects of the sacred history of Islam.there is no disagreement on the Quran and the prophet.that is,on what constitutes the origin of the islamic religion.the difference in view begins with the period immediately following the death of the prophet.one might say that the personality of the prophet contained two dimensions which were later to become crystallized into Suunism and Shiism.each of this two schools was later to reflect bck upon the life and personality of the prophet solely from its own point of view,thus leaving aside and forgetting or miscinstruing the other ddimension excluded from its own perspective.for shiism the dry (in the alchemical sense) and austere aspect of the pesonality as reflected in his successors in the Sunni world was equated with worliness.while his warm and compassionate dimevsion was emphasized as his whole personality and as the essence of the nature of the imams,who were considered to be a continuation.