Chapter X.--The Simple Nature of the Soul is Asserted with Plato. The Identity of Spirit and Soul.
It is essential to a firm faith to declare with Plato  that the soul is simple; in other words uniform and uncompounded; simply that is to say in respect of its substance. Never mind men's artificial views and theories, and away with the fabrications of heresy!  Some maintain that there is within the soul a natural substance--the spirit--which is different from it:  as if to have life--the function of the soul--were one thing; and to emit breath--the alleged  function of the spirit--were another thing. Now it is not in all animals that these two functions are found; for there are many which only live but do not breathe in that they do not possess the organs of respiration--lungs and windpipes.  But of what use is it, in an examination of the soul of man, to borrow proofs from a gnat or an ant, when the great Creator in His divine arrangements has allotted to every animal organs of vitality suited to its own disposition and nature, so that we ought not to catch at any conjectures from comparisons of this sort? Man, indeed, although organically furnished with lungs and windpipes, will not on that account be proved to breathe by one process, and to live by another;  nor can the ant, although defective in these organs, be on that account said to be without respiration, as if it lived and that was all. For by whom has so clear an insight into the works of God been really attained, as to entitle him to assume that these organic resources are wanting to any living thing? There is that Herophilus, the well-known surgeon, or (as I may almost call him) butcher, who cut up no end of persons,  in order to investigate the secrets of nature, who ruthlessly handled  human creatures to discover (their form and make): I have my doubts whether he succeeded in clearly exploring all the internal parts of their structure, since death itself changes and disturbs the natural functions of life, especially when the death is not a natural one, but such as must cause irregularity and error amidst the very processes of dissection. Philosophers have affirmed it to be a certain fact, that gnats, and ants, and moths have no pulmonary or arterial organs. Well, then, tell me, you curious and elaborate investigator of these mysteries, have they eyes for seeing withal? But yet they proceed to whatever point they wish, and they both shun and aim at various objects by processes of sight: point out their eyes to me, show me their pupils. Moths also gnaw and eat: demonstrate to me their mandibles, reveal their jaw-teeth. Then, again, gnats hum and buzz, nor even in the dark are they unable to find their way to our ears:  point out to me, then, not only the noisy tube, but the stinging lance of that mouth of theirs. Take any living thing whatever, be it the tiniest you can find, it must needs be fed and sustained by some food or other: show me, then, their organs for taking into their system, digesting, and ejecting food. What must we say, therefore? If it is by such instruments that life is maintained, these instrumental means must of course exist in all things which are to live, even though they are not apparent to the eye or to the apprehension by reason of their minuteness. You can more readily believe this, if you remember that God manifests His creative greatness quite as much in small objects as in the very largest. If, however, you suppose that God's wisdom has no capacity for forming such infinitesimal corpuscles, you can still recognise His greatness, in that He has furnished even to the smallest animals the functions of life, although in the absence of the suitable organs,--securing to them the power of sight, even without eyes; of eating, even without teeth; and of digestion, even without stomachs. Some animals also have the ability to move forward without feet, as serpents, by a gliding motion; or as worms, by vertical efforts; or as snails and slugs, by their slimy crawl. Why should you not then believe that respiration likewise may be effected without the bellows of the lungs, and without arterial canals? You would thus supply yourself with a strong proof that the spirit or breath is an adjunct of the human soul, for the very reason that some creatures lack breath, and that they lack it because they are not furnished with organs of respiration. You think it possible for a thing to live without breath; then why not suppose that a thing might breathe without lungs? Pray, tell me, what is it to breathe? I suppose it means to emit breath from yourself. What is it not to live? I suppose it means not to emit breath from yourself. This is the answer which I should have to make, if "to breathe" is not the same thing as "to live." It must, however, be characteristic of a dead man not to respire: to respire, therefore, is the characteristic of a living man. But to respire is likewise the characteristic of a breathing man: therefore also to breathe is the characteristic of a living man. Now, if both one and the other could possibly have been accomplished without the soul, to breathe might not be a function of the soul, but merely to live. But indeed to live is to breathe, and to breathe is to live. Therefore this entire process, both of breathing and living, belongs to that to which living belongs--that is, to the soul. Well, then, since you separate the spirit (or breath) and the soul, separate their operations also. Let both of them accomplish some act apart from one another--the soul apart, the spirit apart. Let the soul live without the spirit; let the spirit breathe without the soul. Let one of them quit men's bodies, let the other remain; let death and life meet and agree. If indeed the soul and the spirit are two, they may be divided; and thus, by the separation of the one which departs from the one which remains, there would accrue the union and meeting together of life and of death. But such a union never will accrue: therefore they are not two, and they cannot be divided; but divided they might have been, if they had been (two). Still two things may surely coalesce in growth. But the two in question never will coalesce, since to live is one thing, and to breathe is another. Substances are distinguished by their operations. How much firmer ground have you for believing that the soul and the spirit are but one, since you assign to them no difference; so that the soul is itself the spirit, respiration being the function of that of which life also is! But what if you insist on supposing that the day is one thing, and the light, which is incidental to the day, is another thing, whereas day is only the light itself? There must, of course, be also different kinds of light, as (appears) from the ministry of fires. So likewise will there be different sorts of spirits, according as they emanate from God or from the devil. Whenever, indeed, the question is about soul and spirit, the soul will be (understood to be) itself the spirit, just as the day is the light itself. For a thing is itself identical with that by means of which itself exists.