 Spontaneous generation, that is, the generation of life without their being any parents, as when worms grow in decay, is a much discussed issue of medieval physics and metaphysics. The conflicting explanations of the phenomenon by Avicenna and Averroes much determined the Latin discussion until the sixteenth century. While Avicenna holds that spontaneous generation depends upon ever more refined mixtures of elementary qualities which trigger the emanation of forms from the active intellect, the giver of forms (The Healing: Meteorology II.6: On Floods), Averroes explains it with the influence of certain celestial constellations which actualize potential forms in water or earth. Avicenna and Averroes also disagree about the special case of the spontaneous generation of human beings, which Avicenna finds possible, whereas Averroes does not. For Averroes, all spontaneously created animals are not true, but abnormal, monstrous animals (Comm. magnum Metaph. II.15, VII.31, XII.13,18) (Bertolacci 2013a).