Shi'ism is Not a Political Party

The western scholarship that only view Shi'ism as a political movement is factually incorrect. The concept of separation of church and state did not yet exist in the Muslim community, in the 6th century AD. S.H.M Jafri, the author of The Origin and Early Development of Shi'a Islam writes

Those who thus emphasize the political nature of Shi'ism are perhaps too eager to project the modern Western notion of the separation of church and state back into seventh century Arabian society, where such a notion would be not only foreign, but completely unintelligible. Such an approach also implies the spontaneous appearance of Shi'ism rather than its gradual emergence and development within Islamic society. [1]

Reference
Jafri, S.H Mohammad. "The Origin and Early Development of Shi'a Islam,”, Oxford University Press, 2002, p. 6, ISBN 978-0-19-579387-1