Aquinas

Aquinas borrowed and transformed much from Aristotle in order to give a theological picture of the nature of things.  Metaphysics and cognative psychology are worked out by him from Aristotle and then applied to theological topics. 
The Life of Aquinas:  He lived in the thirteenth century.  Born in Italy.  He was a bright student at the University of Naples.  There he met the Dominicans.  Like the Fanciscans, the Dominicans wanted to go off their land and preach among the people.  Instead of living off endowments, they would live off alms.  Dominic emphasized preaching, so study was important.  Aquinas prepared to become a Dominican, but his parents wanted him to be a Benedictine abbot so they took him away from the Dominicans.  But he returned to the Dominicans.  He was sent by them to Paris and made a professor of theology at the University of Paris.  He did a term there as a professor, then went to a Dominican study-house. 
Structure of the Summa Theologica: Question, Arguments Pro and Contra, Author's Response, and Reply to the Initial Arguments.  This was a simplified format from that used in a Sentence-Commentary at the major universities.  He made a simplified structure for the students in the outlying area after he left Paris
Aristotle held some views which contradicted Christian teachings.  For instance, he believed that the world is everlasting.  Aquinas was called back to Paris for a second term as professor to write commentaries on Aristotle.  
The issue: where was Aristotle compatible with Christianity (and incompatible).   Aquinas wanted to show that Aristotle could be used by Christians (directly and transformed).  Aquinas integrated some platonic thought into his own theology, so Aquinas was not just applying Aristotle to Christian theology. Further, Aquinas displayed conceptual innovation on the work of Aristotle. For instance, Aristotle believed that the soul is the form of the body.  So, the soul could not exist without the body.  Aquinas, wanting to argue for the Christian theology of an after-life, argued that there is another kind of form (of the soul) which can exist without the material body. He died in 1274. Once when he was saying Mass, he had a vision and said that all his theology was straw.  Questios pale (as they are merely articulations on God) in comparison with an experience of God. Controversial: was it a stroke? Later, he died. He left his Summa unfinished.
Aquinas believed that academic disciplines are not separate.  It was a controversial position.  He took many such positions.

9/18/95
Aquinas, On Being and Essence:  Being can stand for the truth of a proposition or for a real thing, divided into ten categories.  Aristotle distinguishes ten categories of real things: substance, quantity, quality, relation, place, time, being in a position, action, and passion.   Aquinas: each of these is a genus, to which differentia could be added to get a species.  For instance, Substance: corporeal (v incorp.), animate (v. inanimate), moble (v. immoble).  These further differentia give rise to different species.  The whole subdivided system is called Porphyry's Tree.  The species is defined by its genus and the differentia of the genus.  A subspecies can become a genus to which another differentia is applied to give rise to a new species. The tree goes down to individuals which are not species. For Aristotle, 'substance' is the main category; the other nine categories are accidents which depend on 'substance' for their being.  Substance does not depend on accidents. 
An essence is that through which and in which a thing has its existence.
We don't predicate the parts by their wholes, but genus can be predicated by their species.  Sam is not his body but he is a human.  Therefore, genus does not signify a part of a species or species of individuals.
To relate being and essence to genus and species, Aquinas looks at the ways in which being and essence are in the world by looking at substance and accident.  Aristotle took the hylomorphic view: matter is formed, rather than the atomist (matter is made up of atoms).  Aquinas followed.  Form gives one more explanatory power to explain genuine beings than that of abstract atoms.  Aquinas lost sight of Aristotle's 'stuff-thing' distinction.  Aquinas uses 'act-potency' instead.
Matter and form are theoretical entities.  Aquinas uses them to explain things and how they act.

Four arguments (roles) of matter:
1. From Logic: The being of a subject is distinct from the being of the predicate. For instance, 'Socrates is white'.  The being of Socrates (subject) is distinct from Whiteness (predicate--a quality and an accident).   But, 'Socrates is Man': the subject and predicate are not distinct in their being, so distinguish prime matter from substantial  form.  These are the metaphysical principles that constitute the power of a substance.
2. From Physics: Aristotle--the substance properties endow something as capable of functioning in certain ways.  Only when being capable of being modified is something changeable.  Adams: this works well for accidents, but what about substance?  What of a substance persists through a change? That which persists is prime matter (which takes on different accidents in the change).  In an Aristotilian change, there must be something that persists through the change: prime matter in a substantial change and substance in changes of accidents.  Prime matter has potentiality (and actuality only with forms). Aquinas: two counter-examples in his theology: transubstantion and creation.  To Aquinas, creation is 'from nothing'.  So, Aquinas likes Aristotle's model here from Physics, but sees problems in applying it to his theology. 
3. Matter and individuation:  what individuates?  Not prime matter because it is in every substance.  Not quantity alone because it is an accident and substance does not depend on accidents.  Matter signed by quantity is responsible for individuation.  Prime matter with quanity is 'extended'.  But, this has an accident playing a role in a change in a substance, albeit the substance (prime matter) is involved.  Form (extention) gives prime matter the capacity for individual. Also problematic: quanity is just as indeterminate as the other accidents.

9/25/95

Substances have a paradigmatic unity, so can't be composites(i.e. agn. atomism).  Rather, there is one actuality component per substance.  Prime matter participates in the actuality of the substantial form.  Matter is pure potentency rather than actuality on its own.  Prime matter subsists through changes borrowing actuality from substantial form.  Prime matter is potency: inbetween nothing and actuality. 
God is infinite actuality.  Creatures participate in it.  Whereas God is simple and One (neo-Platonism), creatures are composite of actuality received (the essence) and the receiver of actuality(that which limits the essence--matter is the ultimate limit here).   Receiving is potency-limiting act.  Matter limits by individuation.  It limits the actuality received of the essences from God.  Aquinas uses 'flowing' or 'emmination' language of the neo-platonists.  The recepticles are defined by divine nature.  Here, matter is constricting the potency in that matter individuates. 
So, two notions of matter as potency that work side-by-side in his theory. 
The essence of a substance consist of both matter and form. Aquinas makes prime matter pure potency and yet that which remains through a change (the substratum of substantial change)  in his argument that a substance consists of both matter and form.  These different usages of the role of matter work in this context (argument) but not necessarily in others. 
Aquinas considered being and essence in relation to genus and species.  He deals with the problem of universals in this context.  Essence in composite substances can be considered as well as signified in many ways.  First, as a part as distinct from that which individuates the thing.  E.g. Humanity.  'Precision' means excluding from the concept of  a subject.  So, 'humanity' precinds that which individuates.  So, it can't be predicated by individuals unlike genus or species, so essence as a part can't be a genus or species.  Second, essence can be considered as a whole absolutely or as it exists in a particular individual(numerically multiplied in many--individuated).   In the latter, it could exist 1. in the intellect or 2. in having accidents accompanying that mode of existence or is equally predicable of many.  Of the latter (has accidents), essence is universal and thus as genus and species.  
Essence as a whole--e.g.: homo.  In so far as homo exists in Socrates, it is numerically one and many subjects can be predicated by homo and has accidents.  Yet, genus and species are both common.  So, essence as a whole, because it can be individuated, can't be a species or genus.  Essence considered as a whole and absolutely: the concept is not wholly determinateable--esp. as pertains to 'one' or 'many' as well as being in reality or the intellect.  It can pertain to existance in the intellect or existence in reality--the same essence leading a double life. Its ontological status is indeterminate. Genus and species are not indeterminate in this sense.  So, it is not genus or species in this sense. 
So, essence is related to genus and species as it has accidents accompanying a mode of existence or is equally predicable of many, but not as a part which is distinct from that which individuates a thing or as a whole as an absolute or in the intellect.

On the Angels:  They are not empirical entities for us.  There must be a reason for positing their existence.  What, for instance, is their ontological status?  Aquinas' reason: God's primary reason for creation was generosity.  Humans don't resemble God in being incorporeal.  If God is motivated by generosity in creating, he wouldn't skip such beings.  Angelic nature is not a composite of matter and form.   Prime matter is not divisible without accidents added (quantitative dimensions).  So, anything material has to be corporeal.  So, angels don't have matter.  Another argument: the created intellect has to have some likeness item of that which it understands (e.g. the species).  When a form inheres in the intellect, a concept exists. When form inheres in Prime matter with quanity, the actual thing exists.  These receiver of an intellect of matter and form limit the intelligibility, so forms are intelligible only separated from matter.  Angels have understanding as their principal function, so there is no matter in angels.  Their understanding should not be limiting (because understanding is their prime function), so their intellect is incorporeal.  So they could not be matter-form composites. 

10/3/95

Soul/Body Relations:
1. The intellectual soul is incorporeal.  He assumes that understanding is the proper function of angels. Humans do it too.  Adams: think of the nature of thoughts.  He claims that our intellectuals understand universal contents.  The same form can exist in prime matter signed by quantity and the intellect.  This is his Same Form Inherence Theory. Knowledge has the same form in the mind as in is in the thing thought of.  This will only adhere if the intellect is not a matter-form composite.  Matter in the intellect would inhibit the intelligibility of the forms known.  This is so because for Aquinas, knowledge involves the same form existing in the knower and the known.  Matter is potency-limiting act. An idea has intentional esse rather than actuality. He qualifies this, however, in stating that there are two ways for a form to be in something: intentional esse and natural esse.  Key: whether the form characterizes that in which it is. Natural esse: yes. So, the intelligible form need not be the same as that in the thing thought of but merely representative of it.  Does this mean that the intellect can't have matter? 
Understanding: forms out of accidents are picked up by the sense.  Does the agent intellect abstract the particular essence of the sensed object--the representation of which is the form in the intellect.  Also, he views the agent intellect as light which contains the intelligible content. 
The formal argument on the incorporeality of the intellectual soul: Because the intellect grasps universal contents, and knowledge involves the same form existing in the knower and the known, and what is received is received after the manner of the receiver, the intellect cannot include matter as  a metaphysical constituent.  Thus, the intellect is incorporeal.  The key: what kind of subject can receive universal esse.  He argues that only an incorporeal intellect can receive universal esse.  It was not self-evident that only a non-material subject could receive a non-material esse (e.g. an idea). 
2. The intellectual soul is incorruptible. To be corrupted means that a matter-form content ceases to be--that the substancial form attached to the prime matter signed by quantity ceases to be. The soul is not a matter-form composite, so it can't be corrupted. 
3. The intellectual soul is subsisting. He assumes that  a form subsists if and only if it has an activity that its (actual or potential) subject of inherence (if any) does not share. So, understanding is an activity of the intellectual soul that the body does not share. 
4. The intellectual soul is the form of the body. Recall the doctrine of the substantial forms.  The soul is the first cause of understanding only when it is adhering in matter because an agent is in first potentiality with respect to sensation only if that agent has a suitable organic body. The key: sensation is essential to understanding by the intellectual soul. 
Aquinas does not believe in innate ideas or intuitive understanding.  Understanding is via sensations.

10/9/95

Soul/Body Relations:
4. The intellectual soul is the form of the body.  Any connection here is for the sake of the soul.  This is Aquinas' view of soul-body relations.  Understanding is a natural functions of human beings.  It requires sensation, which in turn requires a body.  Thus, because the intellectual soul functions in understanding, a suitable organic body is essential to human beings (because it is essential to the soul).  Specifically, having an organic body puts one into first potentiality with respect to sensing.  An organic body is the equipment that could acquire the ability to sense.  The power of sensation gets sensation to second potentiality and first actuality.  So, there must be organic body in order to sense.  Sensation is necessary for understanding which is necessary for the soul. 
But, is human understanding from sensation?  If not, is the activity of the intellect able to be separate from the body.  Does the fact that the soul subsists mean that it could exist without the bodily equipment? 
Aquinas is really committed to the claim that the soul needs the form of the body.  God infused a corruption-inhibitor until the Fall.  The resurrection re-infuses it.  Even then, understanding will be dependent upon sensation.  We can't derive abstract ideas apriori.  The center of Aquinas' philosophy: the soul survives death and it requires the form of the body. So, bodily resurrection is necessary for the subsistance of the soul.  The soul is the only substantial form of the human composite, so it is how that composite gets its esse.  This stace is contrary to the Platonic idea that the form is independent of materiality. 
To say that the soul is subsisting and that it needs the form of the body seems to be saying contradictory things: dualist and non-dualist.  They seem to be saying that the soul can exist alone without the body and on the other hand that the soul requires the body. 
Averroes was a heretic so Aquinas wanted to distinguish his position from that of Averroes.   Averroes argued that there is an intellectual realm with a great chain of intellects.  The human intellect is at the bottom of the line.  These intellectual beings are not matter-form composites and they are not the form of any matter.  They are immaterial by nature.  Human beings are matter-form composites but in which a high-grade sensory soul is most salient.  The human being is a top-of-the-line sensory soul from the stand-point of a hierarchy of matter-form composites.   Averroes thought that humans do not have intellects of our own but we have sensory souls.  So, how can humans understand?  The bottom-of-the-line separate human intellect understands from the human being's phantasms intellible species.  The same form exists in the intellect as in the human matter-form composite.  The human intellect is coupled to the matter-form composite.  So, he would reject the claim that the body is suffcient for the intellect to understand in the first potentiality.  The substances that do the understanding and the sorting are separate but coupled. 
Aquinas wants to rule this coupling theory out to argue instead that the soul is not separated from the body; that is, the soul and body are not coupled together via a shared form, but are not separated.  The soul is the form of the body.  Aquinas states that Averroes does not have a good rationale for the fact that Socrates thinks.  In other words, to Averroes, the human is just the instrument of the intellect.  To Aquinas, the human being is not an instrument of the thinking thing.  Further, to Aquinas, understanding is too incedental to the human being.  To Aquinas, it is essential (internal to its being) that the human being thinks.  Also, Averroes thought that the world is eternal, so there is no first moment.  This went against the Christian doctrine of the creation of the world and Aristototle's view that God is the first cause.   Aquinas wanted to argue against this too.  
5. The Individuation of Souls:
Each of us has our own soul.  How can this be reconciled with the claim that the soul is subsistant?  What individuates is an aptitude for adhering in one chunk of matter rather than another.  An individual form and matter constitute the individual human being.  When the soul actually comes into being, it is made to adhere in a particular matter, with a disposition to adhere in that matter.  This disposition can survive actual non-adherence.  Key: the disposition to adhere in a particular matter, even at death when separation occurs.  Resurrection, because the soul has a disposition to rejoin.  This could only happen by a supernatural cause. Nothing contrary to nature can be perpetual.  Further, ulimate human perfection is not possible, given this disposition of the soul to a particular matter clump, unless the body rejoin the soul.  Finally, the soul must rejoin the body so the individual can come under Final Judgement.
It is a relation to a particular matter, rather than actual adherence, that individuates souls.   It is the tendency to adhere in a particular matter which individuates souls.  It is not actual adherence or anything added to the soul that individuates it.    

10/16/95

Essence and Being(esse):  Their identity and distinction.
Stage I: the otherness (of essence and existence) claim.  Concepts used for a thing's essence and existence are different.  Adams: so how could you get a distinction of a thing as it is as itself?  How could one know the metaphysical composition of what is really out there? 
Aquinas premises that unless an essence is identical with its existence, the essence can be understood without its existence being understood.  But could not there be other elements in an essence? 
Stage II: There is at most one essence identical with existence.  So, other essences, such as under genuses or species, are not identical to their existences.  He assumes that there are only three ways to multiply.  None of them can result in something that is simple (whose essence=its existence) because each of the three ways of multiplication results in composites.  So, there can't be more than one thing whose essence is identical with its existence.  Adams: this does not necessarily mean that there is one; only that there can not be more than one.  So, the existence of a thing whose essence=its existence is not proven here.
Stage III: a principle of sufficient reason.  There is an essence identical to its existence which is the first cause of existence in all things. From a distinction of essence and existence in creatures, the identity of them in the first cause (God).  Adams: But that there is a first cause has not been proven.  Also, in other arguments, Aquinas argues from the identity of essence and esse in God to their distinction in creatures.
So, Aquinas assumes in some parts of his argument the existence of God.  But this is what he is trying to prove.  To Aquinas, the first cause (that which whose essence is identical with its existence) is the pure act.  Adams: the existence of a series need not be assumed for this. 

11/6/95

Aquinas' Action Theory:
Aquinas believed in agent, rather than event, causation.  Every substance is an agent cause.  Every agent acts toward a given end.  This is a metaphysical basis.  Every agent acts for the sake as an end, because everything has an active power as defined by the objects.  A nature is just a complex of powers.  Nature-constituting powers constitute an end.  An agent moves only by determining an end.  A power is a power to do something or be effected in some way.  Powers are aimed at their objects.  The aim of a power is its telos.  Being aimed toward an end is an internal structure or constitution of a thing. Nature is that which has an internal principle of motion or activity.  This is how all things are structured.  Functional explanations are primary in biology, so we need to think of biological beings as being constituted toward an end.  What of non-living things?  Aris: the basic elements are not things but are stuffs, but Aquinas doesn't use this distinction.  So, non-living things are teleological.  But, Aquinas distinguishes between agents having reason and will and those that don't.  Rationality distinguishes those which order themselves to an end from those that must be so ordered by others.  Necessary to conceptualize an end as well as the means thereto for one to order oneself to an end.  This involves one to append universals, so only beings with reason can do it: be self-legislators.  Aquinas claims that rational beings are self-orderers.  Rational agents are self-movers.  Other living beings are not self-legislating.  In what sense are human agents self-movers different from other living beings that can move themselves?  Inward principles of motion vs. outward.  This is sloppy.  Metaphysical natures apply to all created natures.  The difference between self-movers and quasi-self-movers lies in rationality.  Rational calculation is necessary to be self-legislating.  Basically, to be voluntary is to do certain repetitive operations in response to rational self-calculation. 
So, all agents act toward an end.  Different rationales according to the kind of agent.  The capacity for self-legislation makes one kind of agent more Godlike than another.  Rational agency is about ethics.  So, we should aquire virtues that enhance our cognitive ability and thus make us more Godlike. 
There is unity of ends, rather than an infinite progression.  God orders all to the over-all end of the universe.  Infinite causal chains don't explain anything.  A sufficient explanation: the principle of sufficient reason.  There must be a sufficient explanation of everything. Positing a first cause whose existence and activity is self-explanatory would provide such an explanation; an infinite series of causes would not. 
On there being one ultimate end: If powers do not essentially integrate to focus on one object, then they do not constitute a nature. There is an integrated aim at an ultimate end within each individual person. Humans are of the same nature (a nature is simply an integration of powers focused on an end).  So, things of the same species have the same ultimate end.  God is that ultimate end. 
This is Aquinas' metaphysical framework.  Rational agents are not constituted by sufficient powers to be self-coordinating.   Customs suppliment here.  Virtues are examples. 

11/6/95

Aquinas' Action Theory:
Humans are distinct in being self-movers from inward principles (intellect and will, by reason).  God is the first mover, so every creature must involve some external principle of motion.  'Violent' motion is a movement contrary to how the thing's inward principle of motion would go.  It does not necessarily mean being moved by an external object (eg. it could be gravity). That which is not contrary to motion can be either with or without cognition.  God, on the other hand, has only its own internal principle.  Humans are self-legislators, able to distinguish and consider means and ends.  So, human voluntary action can't be violent. 
Adams: Aquinas could be clearer about what self-motion is.  What seems to be key for humans is the ability to self-legislate.  Ignorance can impede this.  For instance, ignorance of premises.  How did we get to be ignorant?  How does it impact what we choose?  Kinds of ignorance: antecedent (not ignorance corrigable or easy to reverse).  This kind of ignorance is excusable.  Consequent ignorance is cultivated (capable of being overcome with reasonable effort).   This type is not an excuse.  Concomitant ignorance(ignorant of what is really happening, even though one would have done the action anyway).  This latter type of ignorance doesn't make any moral difference.  The result would be the same. 
Besides ignorance, sensory passions can obstruct the ability to self-legislate by abstraction or by affecting what appears good to reason.  By abstraction, he means that passions and reason come from the same energy source.  So, if the soul's energy is used up by the passions, then there will be little energy left to calculate by reason.  Passions can cause us not to think straight.  So, passion can interfere with legislation and thus moral action.  Ideally, passions should be moderated by virtues (from Aristotle).  Virtue also helps one to self-legislate in a way in line with the ultimate end (God).  He wants the passions to get their proper objects that is done by reason getting its proper sensory input.  So, Aquinas does not want passionless humans.  Habits enable one to coordinate the intellect with the senses and the passions such that one can be self-legislative towards an appropriate end.  A correct syllogism should go through your mind prompt and easy. 
Aquinas claims that there are degrees of seriousness of sinfulness.  Sins of ignorance and of weakness (from passions) are less serious than sins of malice.  All natures and all natures-consituting powers aim at the proximate good of the agent (being like God).  So, even sins of malice do not aim at the bad.  So, sins of malice, like the other two types of sin, are a distorted way of aiming at the good.  Sins of malice are in terms of incomplete knowledge.  Sins of malice aim at a better-loved good, but secondarily at the cost of doing the evil that accompanies it.  Long-range evil consequences are missed (ignorance). Even so, a more complete knowledge is exercised here than in the case of the other two sins. 
For Aquinas, Being and Good are indistinguishable.  So, is the will deficient in these sins to seek being?  The will without will-power is deficient in being in that it lacks certain accidents such as habits. 
Isn't Aquinas overly optimistic? Can't one will the bad for the sake of the bad?  He thinks that this is metaphysically bizarre.  So, instead he has sinners willing things apparently good (with evil side-effects). Our cognitive power can be mistaken.  In other words, he won't admit that sinners want to do evil because of his neo-platonic metaphysic.
Aquinas sees sin as an offence against God as well as as an error.   Error in relation to God and nature.  Abalard and Anselm: the outward act does not effect the moral evaluation.  Aquinas: the outward act is subject to moral evaluation just as the voluntary action/intension.

11/27/95

Sin: a deprivation in falling short of natural, artifactual, or moral functional norms that are used for habits that are used in seeking God.  This is a metaphysical and theological basis of sin.  Thus, sin is a defect or lack of a good in something that properly ought (by nature) to have it.  Metaphysically, sin is not something in a positive sense, but is rather a deprevation of something else.  Thus, one could not aim at evil; rather, one's aim could be distorted from the good.  Created natures are ways of imperfectly imitating God by seeking Him.  A sin is a fault in the execution of that search. 
An angel is an incorporeal intellectual/rational nature that can contemplate God by power of its own nature but needs supernatural power to see God.  The end of such natures is happiness. 
The intellectual/rational nature malfunctions due to mistaken estimates by the intellect/reason or to the will's failure to follow them.  Human reason can malfunction due to invinciple ignorance, ignorance due to the passions, or to a failure to consider factors relevant to the evaluation of the action in question.  Aquinas: Angels malfunction by failing to consider what they know: factors relevant to the evaluation.  Unlike Anselm, Aquinas does not consider the possibility that angels malfunction due to invinciple ignorance.  Adams: a weakness in Aquinas' system.  To Aquinas, the sin applicable to angels is limited to pride and envy. 
Aquinas wishes to distance God's responsibility of the fallen angels.  God created angels happy as to their natures(contemplating God) but not supernaturally happy(seeing God).  The angels could not have sined in the first moment of their existence because God cannot be the cause of sin, for a thing's functioning at the first instant of its existence would be due to the cause from which it derived its existence.  But God produces angels in existence and conseres creatures in existence throughout their existence.  But some angels willed against their proper subordination to God, probably immediately after the first instant of their creation, while most angels persevere in being oriented to God as the object of their happiness.  Aristotelian optimism: because sin is contrary to natural inclination, and natures function well always or for the most part, more angels persevered than fell.  This is not so for humans, due to our composite nature (evil in most, good in fewer). 
The existence of angels: on the ground that they are what self-diffusing Goodness would produce to fill in gaps in the Great Chain of Being and Goodness. 
Human nature: a hylomorphic composite and so numerically multiable, having corporeal and spiritual levels.  The Fall was not necessary, but is punishment for Adam's sin. All human beings are descended from Adam, and all of his descendents participate in the guilt of his first sin.  This a biological basis for the spread of Adam's sin. But Adam's sin can't be morally imputed to his posterity.  But, many humans are counted as one because they participate in  or share the same human nature.  Just as what the hand does can be attributed to human as a whole and so to its other parts, so what Adam did can be attributed to other members of the human race.  This is a metaphysical(Divine legislation) rationale for the effects of Adam's sin spreading (damaged human nature).  But what was lost (stabilizers) is a gift lost from human nature, so how could human nature be impaired and thus damage being passed on?  So, Aquinas uses both biological and metaphysical rationales for the spread of Adam's sin.  Inconsistent?  In either case, the spread was done as a punishment for Adam's first sin.  God is punishing the human race for Adam's first sin.

12/4/95

Christology:
The incarnation is metaphysically possible, decent, congruous, and of propriety.  On its possibility, he distinguishes essence taken as a whole in the intellect from essence considered as a part.  What is the relation between the universal human nature (an abstract concept) and the individual persons who are human?  He argues against Aristotle's claim that there is a one-to-one correlation between universal substances and individuals. Aquinas: On the trinity, for instance, there is one substance and three supposits.  That substance is not numerically multiplied by the three suposites. But, these three supposits share the same essence, so there is not a one-to-one correlation. The supposits are of a distinction of reason, rather than being a distinction in being.
On the incarnation:  the divine and human natures, retaining their own essences and yet unified.  For the Divine Word to assume the human nature, it must be really distinct from that nature.  Aristotle would assume a one-to-one relation; the divine nature has only one assumed human nature.  This is not so here; a particular human nature is supposited by the Divine Word, but more than one particular human nature could be so assumed.  Being assumed is a real relation of reason in the Divine Word; the particular human nature assumed takes on the esse of one of the supposits of the Divine Word.  Divinity is one essence, with three supposits.  A particular human is assumed passively; that particular human nature is assumed passively such that the particular human nature is related so to the Divine Word without losing its distinctiveness from the divine word.  The co-relation is one of reason, since they have different ontological statuses.  Aristotle: knowing involves a real relation that changes the thing that knows.  It is a relation of reason.  The relation in the nature assumed(to the Divine Word) is real, whereas the relation of the Divine Word (to the particular human nature) is reason.   Why: the relation to the Divine Word changes the human nature (but the human nature, though divinized, is still distinct from the Divine nature)--thus, it is a real relation.  But the thing assumed does not change the Divine Word, so this relation is only of reason (can't be real).   A particular human nature shares the esse of the Divine Word.  A particular substance nature is not its own esse when it shares in the supposit of something else.  The Divine Word uses all of creation as an instrument, but that particular human nature that is assumed participates in the Divine esse whereas the other particular human natures would not, but would form their own supposits.  Any particular human nature could be assumed.  That the Divine Word assumes one changes that particular human nature in that its esse no longer subsists in its own suppository, but in one of the supposits of the Divine Word.  The assumed human nature therefore loses its own esse and takes on that of one of the Divine Word's supposits.  Because a universal and particular need not be in a one-to-one relationship, a universal (the Divine Word) can assume more than one particular human nature.   Each human has their own particular human nature, so there can be more than one incarnation.  That this is possible and not actual is a conservative position taken by Aquinas, based on his interpretation of Scripture.
The particular human nature assumed does not have an esse from its own supposit; the others do.  The particular human nature assumed has a real relation to the Divine Word because that nature's esse changes from itself to a supposit of the Divine Word, and thus really changes.  The Divine Word which assumes a particular human nature has a relation of reason to that nature because the esse of the Word does not change (so the relation is not real, otherwise the esse of the Word would be altered by taking on the relation).  The basic idea is that the esse of the Word does not change whereas the esse of the nature changes.     

12/11/95

Sacraments:
In general, he does not see our bodies as imprisoning our souls.  But, the body is for the benefit of the soul.  So, there is some hierarchy.  Further, revelation and grace complement rather than replace nature.  So, it makes sense that God would become incarnate in a human body and it makes sense that God would work through materials of this world as signs of grace.  Sacraments are not just signs, but are instrumental causes, of grace in the soul.  The grace flows through the instrumental causes (sacraments).  Something material can be part of an instrumental cause of something immaterial.  God is the principal agent.
Root of disagreements on the sacraments: different views of causality.
The Eucharist: 
The Eucharist participates in the divine in a unique way among sacraments in that the body and blood of Christ are really present.  What is the meaning of 'really present'?  Augustine: it is a symbolic spiritual presence; the liturgy is a drama.  Nothing happens to the bread and wine; they are signs of a spiritual presence.  In the eighth century, Radbertus claimed that the bread and wine change internally to become the body and blood.  A real change.  Ratramnus: supported Augustine's stance.  The debate tended to favour Radbertus' stance.  Later, Bergenger of Tours claimed that it was a symbolic change on the grounds that otherwise the accidents and substance would have to exist separately.  Lanfranc insisted that accidents and substance can exist separately.  He won.  But, other views outstanding:
Impanation: The Body of Christ assumes the substance of the bread the way the Divine Word assumes the human nature of Christ thus licensing mutual predications.  Incarnational view: both 'human' and divine natures, each retaining its distinctiveness yet being unified. There is no internal change in the divine Word; it is a relation of reason from the Word to the bread.  Nothing is happening to the bread.  So, nothing is said of the nature of the bread.   Aquinas: bread is a nonrational nature, so it can't be assumed.  
Transubstantiation: the accidents of the bread are no longer accompanied by the substance of bread but accompanied by the substance of the Body of Christ.  Unlike the annihilation view, the change acts on the whole substance of the bread. Annihiation, one substance is taken away and another comes. 'How' is not considered in that view.  A problem with the transubstantiation view: Aristotle: accidents must adhere in their substance.   So, a new metaphysic was needed for this view.
Annihilation: The substance of the bread is annihilated, but its accidents remain, when the Body of Christ comes to be present.  How one substance came to replace the other is not considered.
Consubstantiation: The bread remains and the Body of Christ comes to be present along with it.
Why not allow all of these?  The issue was important then, and the Church wanted to have the best account. But, the council of Lateran IV did not explicitly exclude any of these options. It is not clear that transubstantiation was the chosen view. 
What is 'Body'?  It is a substance that can have its accidents or the accidents of something else.  Very few folks believed that the accidents of the body were present by extention (e.g. chemical change). This is not to say that there are no accidents of the Body along with the accidents of the bread present.
 Aquinas: transubstantiation. He is trying to give an explanation on the how of the change.  Being present by the power of the sacrament rather than by natural comcomittance, does not involve extension (e.g. having it accidents of extension there).  So, the Body of Christ can be on the table and yet in heaven ruling.  It's quantity (an accident) is not extended in place in the way that other substance's quantities are(natural comcomitance).  Further, the substance of the Body can be present without its accidents. 
Real presence: it is a metaphysical change on the altar rather than just a symbol or a spiritual experience of God.  This question was salient due to reverence to the elements in practice.  That began in the eighth or ninth century.  It was quite different from the early Church practice of communion or Augustine's view of the elements.  The theologies of the real presence came out of the practice whereby the elements themselves were revered or worshipped.  Aquinas wanted to say that the substance of the bread wasn't there so that it would not be idolitry.  Scotus: but one is still bowing down before bread-accidents.  Even so, Scotus did not view it as idolitry because he believed that the Body was present.