The ordinances of Islam are of two sorts:
For the first, Shariah is the basis and foundation. This sort is pure and true good.
For the other, Shariah is modifying and justifying. That is, it removes from a most savage and cruel form to a form that is the lesser of two evils (ahwan-ash-shar). It is rectifying, making it practicable for human nature, and in order to make it possible to move on to pure good, has been cast in a form taken from time and place. For it would necessitate reversing human nature to suddenly do away with a matter which prevails over it. Thus, the Shariah did not impose slavery. Rather, it reduced it from a most savage form to one which would open the way to complete freedom; it adjusted and rectified it. Also, the Shariah did not raise the number of wives from one to four - although polygamy is conformable with nature, reason, and wisdom. Rather, it reduced it to four from eight or nine. And in polygamy particularly it imposed such conditions that no harm at all can be caused in the practice of it. And even if there is any bad in certain points of it, it is the lesser of two evils. And the lesser of two evils is relative justice. Alas, there cannot be pure good in every situation in this world!