This shows that there is a struggle between what we call life and the life which is behind it. In Sufi terms we call these two aspects of life Qaza and Qadr: Qaza, the unlimited aspect of life, and Qadr, the limited aspect in the background. Qadr draws upon the life of Qaza for its existence, and Qaza waits, its mouth open to swallow whatever comes into it. Therefore the adepts and the wise, those who are called mystics or Sufis, have discovered the science of how to withhold the experience of life from the mouth of Qaza, the ever-assimilating aspect of life. If we do not know how to withhold it, it will fall into the mouth of Qaza; for Qaza is always waiting with open mouth, just as an illness awaits the moment when a person is lacking in energy. So in all different forms Qaza is waiting to assimilate everything that comes, which is then merged in it.