While reading some of the material, I encounter that in Islamic theology the number of souls need not be constant, for creation has been interpreted as a continuous process. The belief in transmigration (rebirth in forms other than human) as a systematic upward progress towards deliverance was developed by Islamic Philosophers like Ibn Sînâ (Avicenna),who thought of the soul as ‘the principle of self-direction and growth in a body’. Hence, everything inanimate and animate has a soul; inanimate matter also has a measure of creativity ‘akin to that of the First Cause, for it is an emanation of that cause.’ In Ibn Sînâ’s theory of evolution, the soul evolves from vegetable soul to animal soul to human soul which alone can be described as a rational soul. There is a famous poem by the Persian mystic Jalâl u’D Din Rûmî: I died as mineral and became a plant, I died as plant and rose to animal, I died as animal and I was Man. Why should I fear? When was I less by dying? Yet once more I shall die as Man, to soar With angels blest; but even from angelhood I must pass on… A slightly different idea comes out in an anecdote about the Sûfî Abu Yazîd of Bistami. Abu Yazîd was walking with his disciples; the road narrowed, and a dog approached from the other side. Abu Yazîd retired, giving the dog right of way. A disciple wanted to know why, when God had honoured man above all creatures, Abu Yazîd ‘the king of the gnostics’, with such a large following, had made way for a dog. Abu Yazîd’s answer was that the dog mutely asked him: ‘what was my shortcoming, and what merit did you acquire [in your previous life], that I am clad in the skin of a dog, but you are robed in honour as the king of the gnostics?’
There were those like Ibn al-Fârid who poetically ridiculed this theory: ‘Have nothing to do with one that believes in naskh (the transmigration of soul into human bodies)—for his is a case of maskh (the transmigration of souls into the bodies of animals) … And let him alone with his assertion of faskh (the transmigration of souls into plants)—for if raskh (the transmigration of souls into minerals) were true, he deserves to suffer it everlastingly in every cycle.
So I can see that there are multiple beliefs systems coined by falsifas but what is most predominately used philosophy in daily life of a Islamic person?