An Article on Angels by Prof. Edward Feser

Any interest in Angels? Professor Edward Feser is an Aristotelian and Thomist (as in St. Thomas Aquinas) and I have a number of his books. In general, if you are interested in philosophy at all, Edward Feser's blog is great, and it has a wonderfully extensive list of links to a wide-range of blogs and websites. Here's the link to the Professor's essay:
http://edwardfeser.blogspot.hu/2017/07/cartesian-angelism.html

Specifically, the article is partly about the nature of Angels via St. Thomas Aquinas, and also about the substance dualism of Cartesian Philosophy. A great deal of the discussion about the nature of Angels goes on in the Comment section.

The professor also has a link to the relevant Angel section of St. Thomas's Summa.

An excerpt:

You do not have to believe in angels in order to find the notion of philosophical interest.  Working out the implications of the idea of a purely incorporeal intellect is useful for understanding the nature of the intellect, the nature of free choice and its relationship to the presence or absence of the body, the nature of time, and other issues too.  In fact there is such a thing as rational angelology, and here as elsewhere Aquinas often surprises with his demonstration of how much might be established via purely philosophical arguments.

The position of angels in the hierarchy of reality illuminates the similarities and differences between the kinds of things which exist (or, if you don’t believe in angels, which could exist).  At the bottom of the hierarchy come inanimate material things – rocks, dirt, water, and so forth.  Next come the vegetative forms of life, which take in nutrients, grow, and reproduce themselves but do nothing beyond this.  Then we have sensory or animal forms of life, which carry out the vegetative functions but add to them sensation, appetite, and locomotion or self-movement.  Above mere animals are rational animals or human beings.  Human beings do everything other animals do, but on top of that possess intellect and will; and for Aquinas and other Scholastic thinkers, these are incorporeal activities.  A human being is, accordingly, the kind of substance which possesses at the same time both bodily and non-bodily attributes.

Now, there is, as it were, metaphysical room in between human beings and God for a further kind of thing – something which is entirely incorporeal rather than being merely partially incorporeal (as human beings are), but which is nevertheless finite and in need of being created (as God is not).  That is what an angel is.

On Aquinas’s analysis, among the things we can say about angels are the following:

1. Being utterly incorporeal by nature, angels lack sense organs or brain activity.  They do not have sensory experiences, or the mental imagery that follows upon these.  Hence their mode of knowledge is not like ours.  We come to know things through the senses, and form concepts by abstracting them from the things we experience.  An angel, by contrast, has all its concepts and knowledge “built in” at its creation.  In other words, it possesses innate ideas.

2. Angels are not in time, though they are not strictly eternal either.  What is in time, as corporeal things are, is changeable both in its substance and in its accidents.  What is strictly eternal, as God is, is utterly unchangeable.  Angels are unchangeable in their substance, since they are incorporeal.  An angel is not composed of matter which might lose its substantial form and thereby go out of existence.  It is in this way incorruptible or immortal.  But it can change in its accidents insofar as it can choose either this or that.  This middle ground between time and eternity is what Aquinas calls “aeviternity.”

3. For these reasons, an angel does not know things in a discursive way.  It does not have to engage in processes like reasoning from premises to a conclusion, weighing alternative hypotheses, or otherwise “figuring things out” the way we do.  It simply knows what it knows “all at once,” as it were.

4. Unlike the human soul, an angel is not the form of any body.  A human being, again, is the kind of substance which possesses both corporeal and incorporeal activities.  It accordingly has the substantial form of the kind of thing capable of both activities.  When its corporeal side is destroyed, the substance itself is not thereby destroyed, because it was never entirely corporeal in the first place.  That is why the human soul carries on beyond death – qua substantial form, it continues to inform the now incomplete substance of which it is the form, a substance reduced to its incorporeal operations.  But this is not its natural state.  In the absence of matter, the substance in question cannot do all the things it is naturally inclined to do (seeing, hearing, walking, talking, etc.).  But angels are not like that.  Being incorporeal is their natural state.

5. All angels fall under the same genus (which is why they are all angels), but there cannot be more than one member of any angelic species.  The reason is that, for Aquinas, matter is what distinguishes one member of a species of thing from another.  Hence, since angels are completely incorporeal, there is no way in principle by which one member of an angelic species could be distinguished from another.  If there are two or more angels, then, there are ipso facto two or more angelic species.  The way these species differ is the only way they can differ in purely intellectual substances, viz. degree of intellectual power.

See (among other works) Summa Theologiae I.50-64 for more details.  But this much gives us enough to understand why, from an Aristotelian-Thomistic point of view, the Cartesian view of human nature is deeply mistaken.