Why are there more than one school of law?
Laws change according to ages. Prior to the Seal of the Prophets, at
times it happened that in one age different Prophets came to different
peoples with different laws. After the Seal of the Prophets, upon him be
peace and blessings, however, since his most comprehensive Shari'ah is
sufficient for all the peoples in every age, no need has remained for other
laws. Nevertheless, in secondary matters of the Shari'a, the need for
different schools has remained to a degree. Just as clothes change according
to seasons and cures may differ according to temperaments, so too with the
change of ages and according to the characters and capacities of peoples,
the rules for the secondary matters of the Shari'a may differ. Because those
secondary matters are concerned with human temperaments and the prevailing
conditions of the time, they come according to them and become like cures.
At the time of the early Prophets, peoples were distant from one another
both physically and with respect to the level of education, and their
characters were somewhat coarse and violent, and their minds, primitive. For
this reason, the Laws which came at that time were all different and
appropriate to their conditions. There were even different Prophets and Laws
in the same region in the same age.
Then, since the Last Prophet came with an all-comprehensive religion to
lead mankind to pass to the secondary and further stages in science,
education and civilization, and to enable them, through numerous revolutions
and upheavals, to reach a position at which all peoples could receive a
single lesson and listen to a single teacher and act in accordance with a
single law, no need remained for different Laws, neither was there any need
for different teachers. But because they have never been all at completely
the same level and led the same sort of social life, there have been
different schools of conduct. If, like the students of a school of higher
education at al-most the same level with one another, the absolute majority
of mankind were to lead the same sort of social life and attain the same
level, then all the schools could be united. But since the conditions of the
world do not allow that, the schools of law cannot be the same.