The number of the fundamentals (Usool-e-Deen) is a theoretical
issue. It means that some issues because of their importance in terms of
being the pillars of the religion or the distinguishing aspect of this
school (Shia) from others (in terms of faith) or because being
fundamental for the practical and belief aspects, became part of
Usool-e-Deen. Which in reality is a kind of overall view of a religion
or school. It means that where possible we should interpret religious
issues to one fundamental point in order that learning, teaching &
propagation is simplified.
It is not that we have a verse or narration stating the number of
Usool-e-deen to be five viz, Tawheed, Nubuwat, Ma'aad, Adl & Imamah. Of
course all these five have been explained in the Quran and Hadith. The
reason for expressing just these five is their importance. If not, all
these five could be summarized in one, which is Tawheed or any other
fundamental, which in reality returns to one whole. Some scholars
expressed 150 fundamentals or more. It depends on our goal. Do we want
to introduce religion in its brevity or in detail, each of these have
many categories. As a result, Tawheed, Nubuwat and Ma'ad are the most
basic believes in all revealed religions. We could count other beliefs
as part of basic beliefs, which are achieving from their interpretation
or their dependencies, according to specific term. For instance the
Existence of Allah could be counted as the first principle and the Unity
of Allah could be counted as the second one. Or Nubuwat could be counted
as the principle of all religions and believing in Holy Prophet Mohammad
(saw) could be counted as another principle of Usool-e-deen according to
some Shia scholars. Adl, which is the secondary belief of Tawheed, is an
independent principle and Imamah, which is the dependency of Nubuwat, is
another principle. So the word, Usool-e-deen could be used in two
meanings: a general and a particular meaning.
The general in comparison to the secondary principles (furoo-e-deen) and
rulings includes all aspects of belief. The particular meaning is
specific to the most basic beliefs and does not relate to a period that
it originated from. Nor it means whether its origination is since the
period of the "lesser occultation" but rather they are the same beliefs
that were explained by the Holy Prophet Mohammad (saw).