Notes on Aquinas, Summa Theologiae 1a, q. 84

ST 1.84: How does the human intellect know bodies (which are beneath it)

ST 1.84.1 Does the soul know bodies through the intellect

Objection 1: Bodies are understood by the senses, incorporeals by the intellect

Reply: This refers to the medium of knowledge, not the object

Objection 2: Sense:Intelligible :: Intellect:Sensible.  Since senses can’t understand intelligible things, the intellect can’t understand sensible things

Reply: Intellect is a higher power than sense.  While sense cannot know intelligibles, intellect can know sensibles.  Otherwise God wouldn’t have knowledge of sensibles.

Objection 3: Intellect understands eternal and unchangeable things, while bodies are always changing

Reply: Every movement presupposes something immovable.    Changing form requires unchanging matter.  Changing matter requires unchanging form.  Socrates may not always be sitting, but it is always true that when he does sit he stays in one place.

On the contrary: natural science, with its studies of motion and matter, would be impossible if the intellect had no knowledge of changeable things.

One possible answer: Certain Presocratics (Heraclitus) thought everything was in a state of flux, so certain knowledge of anything was impossible.

Refutation: Heraclitus was only led to this conclusion because of their reductive materialism.

Another possible answer: Plato’s theory of forms

Refutations:

1. If forms are immaterial and immovable, how can we have knowledge of matter and motion?
2. Plato begs the question: How can we know bodies, if we only know them through separate substances which differ essentially from them?
3. Plato assumed that the form must exist in the knower in the same mode as in the thing known.  This is not true.

Whiteness is in bodies in different modes of intensity

The senses receive whiteness without receiving matter

The intellect receives whiteness under conditions of immateriality and immobility

ST 1.84.2 Does the soul know bodies through its essence?

It would seem so.  Knowledge is by assimilation, where the intellect “becomes” whatever essence it is to know.  Thus, the intellect knows all things by the essence it has assimilated, which essence has become the intellect’s own essence.

But Augustine says we know things through our senses.

Presocratic view: the material intellect receives forms materially

Refutations:

1. Matter is only form potentially, and knowledge is of actualized form
2. Why doesn’t matter outside the soul possess knowledge?

Platonist view: The immaterial soul receives forms immaterially

Only God knows things through his own essence; humans and angels don’t

ST 1.84.3 Does the soul know through innate species?

Our knowledge is different from angelic knowledge.  Our knowledge must be brought into act, while angelic knowledge is always in act.  Moreover, the angelic intellect is completed by the angelic form and is not in potentiality with respect to anything.  The human intellect is in potentiality with respect to things it does not know.  Prime matter is in potentiality with respect to its substantial form.

ST 1.84.4 Are intelligible species derived by the soul from separate forms?

The objections proceed by analogy from sense, also noting that the intellect requires something actually intelligible in order to be brought into act.

But if we know by separate forms, there is no reason why our souls should be united to bodies.  Both Plato and Avicenna’s views are considered and deemed insufficient for explaining the existence of the body.

In replying to the objections, St. Thomas says there is no analogy between sense and intellect.  He concedes that divine ideas are the ultimate source of our knowledge, but we attain to this knowledge by the actualization of phantasms by agent intellect.

ST 1.84.5 Does the intellect know material things in the eternal types?

St. Thomas states that Augustine was “imbued with the doctrines of the Platonists.”

St. Thomas makes a distinction:

1. Knowing the eternal types as objects.  The souls of the blessed know things in the eternal types in this way.
2. Having the eternal types as a principle of knowledge.  Just as our senses see by the light of the sun, our intellect sees by the intellectual light which is in us, even as pilgrims.

The human intellect requires both intelligible species and intellectual light in order to know.

St. Thomas shows that Augustine was not as Platonist as he originally seemed.

ST 1.84.6 Is intellectual knowledge derived from sensible things?

Augustine’s argument that intellectual knowledge does not come from the senses

1. Sensible things are always changing, but what is never the same cannot be perceived
2. We cannot tell through the senses whether we are seeing a real image or whether we are seeing an imaginary image (dreaming), but the intellect is capable of perceiving truth
3. What is lesser cannot act on what is greater, so the senses cannot produce knowledge in the intellect
4. We know some immaterial things

Democritus thought all knowledge was by a discharge of atoms

Plato thought the soul forms within itself the species, after the sensible organ receives the sensible object.  The soul is roused by the species of the thing.

Augustine said the body was the messenger to the soul.

The senses rouse the intellect to the act of understanding.

Aristotle said sense is an act not of the soul alone, but of the “composite.”  The sensible is received in the sense by a discharge or some other operation.  Then agent intellect derives the phantasm and ultimately the intelligible species from the sensory input.

Sensible things are only the material cause of knowledge.  Agent intellect is also required.

ST 1.84.7 Can we understand without turning to phantasm?

No, because:

1. When imagination is hindered by frenzy or lethargy, all intellectual operation is also hindered.
2. We all understand by forming phantasms to serve as examples
3. It belongs to a nature to exist in an individual.  This cannot happen apart from corporeal matter.  Since we apprehend the individual through phantasm, we need phantasm in order to see the universal nature existing in the individual.

Interesting facts:

When knowledge is not actualized, intelligible species dwell in the passive intellect.

The intelligible species is NOT the likeness of the individual thing.

Our intellect’s proper and proportionate object is the nature of a sensible thing (?)

ST 1.85.1: Does our intellect understand corporeal and material things by abstaction from phantasm?

3 grades of cognitive powers:

1. Sense organ: object is form existing in individual matter
2. Human intellect: object is form existing in individual matter, but not AS existing in this particular matter
3. Angelic intellect: object is form existing apart from matter

2 types of abstractions

1. Composition or division, i. e. Judgement of truth or falsehood
2. Simple or absolute consideration: consider something and prescind from its principles of individuation

3 types of matter:

1. Individual (“this flesh and these bones”)
2. Common/signate (“flesh and bones”)
3. Common intelligible matter (quantity, number, dimension, figure)

(things like “being,” “unity,” “power,” “act” abstracted from all matter)

“The phantasms are made more fit for the abstraction therefrom by intelligible intentions.”

ST 1.85.2: Are intelligible species the object of our intellection?

No, intelligible species are the species qua, not species quae intelligitur.

Otherwise, science would be about words, not things.

Also, we would have no way of judging the truth or falsity of our ideas.

Intelligible species is a likeness of the thing understood, as heat in the heater is a likeness of the thing heated

Abstract universal exists in the mind, but the universal which is understood exists in its instantiations.

2 operations of the sensitive part:

1. Impression (totally passive)
2. Formation (imagination, active)

2 operations of the intellect

1. Impression (passive intellect receives intelligible species)
2. Formation (active intellect forms definition or judgement)

ST 1.85.3 Whether knowledge of the most universal species is prior?

Sense knowledge is prior to intellectual knowledge.  Therefore in some manner we know the particular first.

However, in the intellect we know what animals are, albeit indistinctly, before we can distinguish rational animals from non-rational animals.

In the senses, we know something is a body before it gets close enough to be known as an animal.  A child calls all men father before he learns to distinguish his father.  Therefore, universal sense knowledge is prior.

Something’s genus is derived from its common matter; the species comes from the form.  Nature ultimately intends the species, not the genus.

ST 1.85.4 Whether we can understand multiple things at once?

No, just as an object cannot have multiple colors at once, an intellect cannot have multiple intelligible species at once

We can, however, understand multiple things in a single species

ST 1.85.5 Whether our intellect understands by composition and division?

Yes, because our intellects achieve perfection by degrees.  We must make a judgement (i. E. a composition or division) about the state of our knowledge in order to attain more perfect knowledge.

Intellectual operations are in time insofar as we have to turn to phantasms

2 types of composition in a material thing

1. Form with individual matter: Man is an animal (form with common matter); Socrates is a man (individual matter with form)
2. Substance with accident: Socrates is white (Socrates as a man possessing whiteness)

2 types of composition in the intellect

1. The whole with the part (form/species with common matter/genus)
2. Subject predicated of accident (identification of Socrates with whiteness)

ST 1.86.6 Can the intellect be false?

The intellectual light cannot err, because the proper object of intellect is the quiddity of the thing.  Provided we are abstracting quiddities from phantasm or deriving first principles from the operation of the intellect itself, the intellect cannot be false.

In composition or division, the intellect can err.

ST 1.86.7 Can one man understand better than another?

1. No, in the sense that all men understand through the same intelligible species.  Either you have the intelligible species or you don’t.
2. Yes, in the sense that one man may perceive the intelligible species with greater keenness than another, as a man with 20-20 vision will see visible objects better than another.
3. Yes, in the sense that intellect’s operation depends on the sensitive and imaginative faculties.  Someone with a better memory, for instance, can understand things better.

ST 1.86.8 Is the indivisible known before the divisible?

1. Yes, in the sense that we know a quiddity indistinctly as a unity before we know it distinctly by understanding its parts.
2. Yes, in the sense that we know simple quiddities of things before we engage in complex composition or division.
3. No, in the sense that abstractions like “point” or “unity” are known only by privation.  A point is “something which has no parts.”  We know things with parts before we can consider something without parts.  This is because these concepts are opposed to natural, corporeal reality.