[88] Or again, how could it fly through the air from earth to heaven, and investigate the natures which exist in heaven, and see of what nature they are, how they are moved, what are the limits of their movements, of their beginning and of their end; how they are adapted to one another and to the universe according to the just principles of kindred? Is it easy to have an accurate comprehension of the different arts and of the different branches of knowledge which bring external things into shape, and which are concerned with the affairs of the body and of the soul, with a view to the improvement of the two, and to understand ten thousand other things, of which it is not easy to describe either the number or the nature in language?