Some have said that the Soul is a spirit or an immaterial substance; others, a kind of divinity; some, a very subtile air, and others a harmony of all parts of the body. Again, others have remarked that it is the most subtile and fine part of the blood, which is separated from it in the brain and is distributed by the nerves: so that the source of the Soul is the heart where it is produced, and the place where it performs its noblest function is the Brain, because there it is well purified from the grosser parts of the blood. These are the principal opinions which have been held concerning the Soul, but to render them more perceptible let us divide them into material and spiritual, and name the supporters of each theory that we may not err.
III.
Pythagoras and Plato have said that the soul is spiritual, that is to say, a being capable of existence without the aid of the body, and can move itself: that all the particular souls of animals are portions of the universal soul of the world: that these portions are spiritual and immortal, and of the same nature, as we may conceive that one hundred little fires are of the same nature as the great fire at which they have been kindled.
IV.
These philosophers believed the animated universe a substance, spiritual, immortal and invisible, pursuing always that which attracts, which is the source of all movements, and of all Souls which are small particles of it. Now, as Souls are very pure, and infinitely superior to the body, they do not unite immediately, but by means of a subtile body, such as flame, or that subtile and extensive air which the vulgar take for heaven. Afterwards they take a body less subtile, then another a little more impure, and always thus by degrees, until they can unite with the sensible bodies of animals, whence (sic) they descend like into dungeons or sepulchres. The death of the body, they say, is the life of the soul wherein it was buried, and where it exercises but weakly its most beautiful functions.
Thus at the death of the body the soul comes out of its prison untrammelled by matter, and reunites with the soul of the universe, from whence it came. Thus, following this thought, all the Souls of animals are of the same nature, and the diversity of their functions comes only from the difference in the bodies that they enter.
Aristotle admits further, a universal understanding common to all beings, and which acts in regard to particular intelligences as light does in regard to the eyes; and as light makes objects visible, the universal understanding makes objects intelligible. This philosopher defines the Soul as that which makes us live, feel, think and move, but he does not say what the Being is that is the source and principle of these noble functions, and consequently we must not look to him to dispel the doubt which exists concerning the Nature of the Soul.