The following explanation of Sufism is taken from the journal Sufism: An Inquiry by Shah Nazar Seyed Dr. Ali Kianfar.
Does everyone have the essential capacity to accept and receive the teachings and the principles taught by Sufis? More precisely, can everyone make the principal focus of their life the cultivation of discipline, learning, and advanced morality? Truthful Sufis have a consensus on this important, though little-discussed issue. The answer is clear in nature: not every human being is capable of receiving, accepting, and understanding spiritual teachings.
Sufis believe that everything is in the hand of Allah. This might seem to imply that anything and everything is possible-but in truth this fact point highlights the same conclusion. Allah has established the harmony of Being, a world governed by laws, including spiritual laws. One of the most basic of these is that there must be a harmony between the sender and the receiver, both in the world of nature, and in the world of the spirit-the two are, for Sufis, one realm of being. In the spiritual domain, such harmony consists in understanding, and that depends upon the inherent capability of the receiver.
The heart of the human being is the locus of receiving spiritual truth, and the truth that the individual is capable of receiving depends upon the qualities of heart. Just as not every individual may be a mathematician, a poet, or an inventor, so also not everyone may receive spiritual teachings, for many lack the necessary basis of understanding. To admit this is merely to accept the nature of being, to acknowledge the evidence of many years of teaching and the long history of Sufism.
Some people may argue against this statement by claiming that everyone is equal, and all can receive spiritual knowledge. But this is not really argument, only empty sloganeering. Indeed, to think in this way is itself a sign of a lack of essential inward understanding, or a poverty of heart. Those who would make everyone equal deny the uniqueness of heart, the reality of humanity, and reduce the human being to the uniformity of a thing. Such people do not practice reason, but instead express their own anger at Being. They question God for His supposed lack of compassion-as if to make everyone the same were to show Divine compassion. In so doing, they merely expose their own lack of understanding: the God that is accused in such a court and by such people is indeed unknown to them.
There is a story told by a Sufi that may be mentioned here:
A group of bandits once infested the mountains, waiting for passing caravans to rob. A king who lived in a nearby city gathered the best of his soldiers and sent them to the mountains to find the robbers. The soldiers found their hiding places, and waited for the bandits to fall asleep. With nightfall, the robbers fell asleep one by one. In the middle of the night the soldiers attacked, captured them, and brought them back to court. The king ordered all to be executed. There was a very young man among these thieves, and the king's minister, taking pity on this youth, asked the king to spare him. Perhaps such a young man could be exposed to a good environment, brought up in a good family, and given teachers to help him to grow to be a better man. The king warned his minister that the boy was a thief, that such was his identity, despite his youth. But the minister begged to be allowed to try. So the king set the boy free and gave the minister the responsibility of educating the boy. Time passed, and in a few years, the boy began associating with unfit friends, stealing, and eventually killing none other than the son of the minister, running away from the city and joining another group of bandits.
The Sufi storyteller ends with this warning:
Rain is delicate and pure. It pours gracefully upon both field and desert, The field grows flowers, and the desert-thorns.