In terms of cosmology, according to Davidson (p. 82) "Avicenna's universe has a structure virtually identical with the structure of Alfarabi's" but there are differences in details. As in Al Farabi, there are several levels of intellect, intelligence or nous, each of the higher ones being associated with a celestial sphere. Avicenna however details three different types of effect which each of these higher intellects has, each "thinks" both the necessary existence and the possible being of the intelligence one level higher.