The lowest celestial sphere, the lunar sphere, also generated lumen, which moved inwards and further concentrated the matter below this sphere. But since this lumen lacked enough power to fully disperse the outermost parts of this matter below the lunar sphere, it produced a sphere comprised of incompletely dispersed matter, the sphere of fire. Likewise, fire generated lumen, producing below it yet another sphere of incompletely dispersed matter, the sphere of air. This process continued, giving rise in turn to the spheres of water and earth, the latter being comprised of the most concentrated and dense matter. Because the matter of these four elemental spheres was not fully dispersed, it remained capable of being concentrated and dispersed, and for this reason the elements, unlike the celestial spheres, are capable of alteration, growth, generation and corruption.