And that, granny, is the million dollar question?
To properly understand “soul” one must first understand the Aristotelian-Thomistic doctrine
hylomorphism, which involves the determinations of being in regard to all natural things. All things from trees to atoms are composed of two metaphysical constituents, substantial
form (
morphe, but more correctly
eidos) and first matter (
prima materia), and as “informed” is often referred to as “substantial matter”.
Form is non-physical or immaterial component of every physical thing. “Immaterial” in this context does not spiritual. It means not-physical and nothing substantially more. It is not exactly a “ratio”; it is the first determining principle and plan of structure.
Now that I have thoroughly confused you, we will take the
hylomorphic doctrine and apply is consistently to living things. Living things possess self-motion while non-living matter is moved extrinsically by other forces. The principle of self-movement or life is the kind of form proper to organisms. We call this form or
eidos, the
psyche or “soul.”
The immaterial forms of living things are generated and corrupted through the natural processes of nature. In the case of man, we must posit a different grade of soul with a different grade of immateriality.
When substantial form is united to matter we have an individual substance, that which sub-stands, or stands under the appearances. In Kantian terminology, it is the noumenal reality which supports the phenomenal aspects of material being.
The form of man is an intellectual form. In-depth considerations of the nature of intellect and its activities, and its relation to the body, require us to posit the soul of man as not only immaterial, but as spiritual. (In general conversation, “immaterial” and “spiritual” are used interchangeably, and correctly so, and are they purely negative terms meaning not-material. The concepts are “negative” in nature since all knowledge begins with sense experience, and so we can have no direct knowledge of that which is not an object of sense perception. I am, however, stipulating in this post, a slightly different meaning for “spiritual”.)
The human soul, to continue, is an incomplete spiritual substance. It is incomplete because its nature is to be united and perfected by union with matter. In so far as it is a substance, it is unlike the souls or forms of non-intellectual organisms which are generated and corrupted along with the organism, but can subsist of itself. Accordingly, we say that the intellectual soul is spiritual and immortal.
This may be a lot to digest, but the key is understanding the philosophical terms, to which there is no easy road, only much intellectual effort. One cannot just read an explanation of the terms and think from that they got it. That is normal.
A great Arabian philosopher in the middle ages, I forget whether it was Averroes or Avicenna, said he had to read the
Metaphysica of Aristotle 40 times before he understood it.