The process of emanation begins (metaphysically, not temporally) with the First Cause, whose principal activity is self-contemplation. And it is this intellectual activity that underlies its role in the creation of the universe. The First Cause, by thinking of itself, "overflows" and the incorporeal entity of the second intellect "emanates" from it. Like its predecessor, the second intellect also thinks about itself, and thereby brings its celestial sphere (in this case, the sphere of fixed stars) into being, but in addition to this it must also contemplate upon the First Cause, and this causes the "emanation" of the next intellect. The cascade of emanation continues until it reaches the tenth intellect, beneath which is the material world. And as each intellect must contemplate both itself and an increasing number of predecessors, each succeeding level of existence becomes more and more complex. This process is based upon necessity as opposed to will. In other words, God does not have a choice whether or not to create the universe, but by virtue of His own existence, He causes it to be. This view also suggests that the universe is eternal, and both of these points were criticized by al-Ghazzali in his attack on the philosophers.