The Six Books of Proclus on the Theology of Plato, Volume 2

For if the distribution of vehicles to souls is according to nature, it is necessary that the vehicle of every partial soul should have the same ratio to the vehicle of the soul which ranks as a whole, as the essence of the one to the essence of the other. The distribution, however, is according to nature. For things which primarily participate are spontaneously conjoined with the natures which they participate. If, therefore, as a divine soul is to a divine body, so is a partial soul to a partial body, each soul essentially participating,—if this be the case, that which was at first asserted is true, that the vehicles of souls have the same ratio to each other, as the souls themselves of which they are the vehicles.