"We are in the habit of recognizing, as one determinate kind of what is, substance, and that in several senses, (a) in the sense of matter or that which in itself is not 'a this', and (b) in the sense of form or essence, which is that precisely in virtue of which a thing is called 'a this', and thirdly (c) in the sense of that which is compounded of both (a) and (b). Now matter is potentiality, form actuality; of the latter there are two grades related to one another as e.g. knowledge to the exercise of knowledge." De Anima II,1

 

In other words, “substance” (ousia) can be pure matter (hyle), pure form (morphe or eidos), or composite.

 

Matter (hyle) is

1.      undifferentiated potentiality

2.      inert

3.      impredicable (nothing can be said about it)

4.      no-thing (formless, hence nothing we can name)

 

We have no experience of undifferentiated matter. Pure matter (prote hyle) isn't anything. Everything we experience is already something — it already has some form.

 

Form is

1.      active

2.      differentiating

3.      the organizing and limiting principle of everything in our world (the Form of X is what makes X's stay X's and not turn into Y's before their time)

4.      actuality, or being, in the sense that if something has Form X, it is an X

 

We have no experience of pure form. Pure form is Aristotle's God, or Prime Mover, who actualizes all potential at once.  Everything we experience is individuated; it is a "something" and hence has a material component.

 

So everything we encounter is composite. In Aristotle’s hierarchy of being, pure potentiality (“prime matter”) is at the bottom, pure actuality (Aristotle’s God) is at the top. Formed matter (everything else, including our world) is in between.

 

For Aristotle, all the composite beings in our world are actually something at any time (because they always embody some form); and each step in the development of that being follows a particular trajectory, according to the kind of being it is. So there is a form of, say, dog, which all dogs possess equally; but individual dogs are different from one another because their matter differs. The doggy form brings with it various potentials: to bark, scratch, pant, etc. As dogs exist through time, they change, according to both their form (all dogs get bigger, older, and so on), and according to their matter (my dog gets bigger because of the specific food he eats, which no other dog eats). Change is the transformation of potentiality to actuality. As my dog actualizes his doggy potentials within his individual life, his scope of possibilities narrows, since our lives are finite.

 

Aristotle's world-view is teleological. For Aristotle, things have natural goals or purposes or functions. When Aristotle says everything has a goal, he doesn't mean everything is conscious, by the way. For Aristotle, most things are not conscious. But the whole universe is set up so things naturally, automatically act to attain full being, or perfection of their being. For Aristotle, this is the same as saying everything's goal is to actually be as fully and completely as possible what it already is potentially. Like Plato, Aristotle believes excellent things are not only better but more real (more actual). Aristotle uses the word entelechy to mean fully realized being that exists within something formally and guides the actualization of its potential toward full being. Entelechy is a kind of form.

 

For example, a knife's function is to cut. A knife is a better knife, and more of a knife (it has more knife being) the better it realizes its potential to cut. Its entelechy is its knifely structure. The structure organizes its matter and at the same time limits and determines the possibilities for that matter. (Matter organized in a knifely way can cut, but it can't walk or carry on photosynthesis. Those limitations are imposed by the entelechy.) The optimal knife, the best knife, the knife with the most knifeness, is the one put together optimally to achieve the natural purpose of a knife. We help this along (by cleaning, sharpening, etc.) or hinder it (by leaving it out in the rain); knives can't be fully knifely without our help.

 

According to Aristotle's famous definition, the soul (psyche) is "the entelechy of a natural body having life potentially within it." (Your translation has: "the soul is the first grade of actuality of a natural body having life potentially in it." The word translated as "actuality" is the word for entelechy.)

 

Since entelechy is form, the soul is the form, or principle of organization, of any living body. It is the actualization of the body-matter that enables the composite to perform its proper function, according to its kind. A knife doesn’t have a soul since it’s not alive. For Aristotle, there are different kinds of soul corresponding to different kinds of living things. They are arranged in a hierarchy such that the higher forms have all the properties of the lower types but not vice versa. The second chapter of the second book of De Anima (in the assigned reading) makes the following distinctions:

 

plant soul:             nutritive or vegetative (able to assimilate nutrients)

 

animal soul:             sensitive (having sense perception, desire, and local motion). Palmer calls this the appetitive soul.

 

human soul:             rational, involving two faculties: (1) the ability to grasp a priori knowledge (epistemonikon) -- whose virtue is theoretical wisdom (sophia) -- and (2) the ability to grasp truths about the changeable world (logistikon), whose virtue is practical wisdom (phronesis).

 

Palmer pictures this on page 59.

 

So soul makes a living thing what it is (it's its form). Living things (like everything else in Aristotle's world) are striving for full and complete being, which means full realization of their potential within the constraints of their type of being, which is the same as performing their proper function with excellence. Plants naturally seek light. They get bigger and bigger up to a certain point (different for different kinds of plants); i.e., they exercise their nutritive capacity to the fullest if conditions permit. Animals exercise their capacities for exploration of their environments (sensing); they'll roam around if they can. Animals have desires and seek to fulfill them, each according to its kind.

 

(There's an important ethical intuition behind all this: that it's wrong to waste or crush potential. Why do we think poverty and injustice are bad, after all? Because oppressed people don't get to realize their potential; they don't get to actually be what they already are potentially. Some animal rights folks make a similar argument about animals. They says it's prima facie immoral to restrict an animal's movements, or its ability to explore its environment, or its ability to reproduce, etc.)

 

Full human being is fully rational being, since for Aristotle, the proper function of humans is to reason. A fully human being is one who exercises his proper function with excellence: he is a good reasoner, with both sophia (theoretical wisdom) and phronesis (practical wisdom). The latter enables him to recognize the GOLDEN MEAN, and thereby act with arete, or "human excellence."

 

Now, what about immortality of soul?

 

1.      Aristotle says, no way! In general, souls require bodies. In other words, there's no such thing as disembodied soul. So forget about immortality. A dead thing can't do its proper functions; it has therefore ceased to be essentially what it was. As Aristotle says: "That is why we can wholly dismiss as unnecessary the question whether the soul and the body are one: it is as meaningless as to ask whether the wax and the shape given to it by the stamp are one, or generally the matter of a thing and that of which it is the matter.... as the pupil plus the power of sight constitutes the eye, so the soul plus the body constitutes the animal. From this it indubitably follows that the soul is inseparable from its body, or at any rate that certain parts of it are (if it has parts) for the actuality of some of them is nothing but the actualities of their bodily parts."

 

2.      Aristotle says, maybe! Maybe some souls, or parts of souls, don't require bodies after all. In Chapter 1 of Book II Aristotle says: "Yet some [parts of the soul] may be separable because they are not the actualities of any body at all." In Chapter 2, he says: "We have no evidence as yet about mind or the power to think; it seems to be a widely different kind of soul, differing as what is eternal from what is perishable; it alone is capable of existence in isolation from all other psychic powers. All the other parts of soul, it is evident from what we have said, are, in spite of certain statements to the contrary, incapable of separate existence though, of course, distinguishable by definition."

 

Aristotle never decides this issue with certainty, but Christian scholars have made much of these passages: they say Aristotle "leaves the door open" for immortality of soul.