saying of our Sages, that the number of the species of plants is the same as that of the individuals included in the general term “stars.” The arrangement of the Universe may therefore be assumed to be as follows: there are four spheres, four elements set in motion by them, and also four principal properties which earthly beings derive from them, as has been stated above. Furthermore, there are four causes of the motion of every sphere, namely, the following four essential elements in the sphere; its spherical shape, its soul, its intellect, by which the sphere is capable of forming ideas, and the Intelligence, which the sphere desires to imitate. Note this well. The explanation of what I said is this: the sphere could not have been continuously in motion, had it not this peculiar form; continuity of motion is only possible when the motion is circular. Rectilinear motion, even if frequently repeated in the same moment, cannot be continuous; for when a body moves successively in two opposite directions, it must pass through a moment of rest, as has been demonstrated in its proper place. The necessity of a continuous motion constantly repeated in the same path implies the necessity of a circular form. The spheres must have a soul; for only animate beings can move freely. There must be some cause for the motion, and as it does not consist in the fear of that which is injurious, or the desire of that which is profitable, it must be found in the notion which the spheres form of a certain being, and in the desire to approach that being. This formation of a notion demands, in the first place, that the spheres possess intellect; it demands further that something exists which corresponds to that notion, and which the spheres desire to approach. These are the four causes of the motion of the spheres. The following are the four principal forces directly derived from the spheres: the nature of minerals, the properties peculiar to plants, the animal faculties, and the intellect. An examination of these forces shows that they have two functions, namely, to produce things and to perpetuate them; that is to say, to preserve the species perpetually, and the individuals in each species for a certain time. These are also the functions ascribed to Nature, which is said to be wise, to govern the Universe, to provide, as it were, by plan for the production of living beings, and to provide also for their preservation and perpetuation. Nature creates formative faculties, which are the cause of the production of living beings, and nutritive faculties as the source of their temporal existence and preservation. It may be that by Nature the Divine Will is meant, which is the origin of these two kinds of faculties through the medium of the spheres.