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Medieval Philosophy – Prof. Dr. Robert C. Koons

http://www.utexas.edu/cola/depts/philosophy/faculty/koons/phl349/syllabus.htm

Lecture # 22: Theory of Knowledge: ibn Sina, ibn Rushd, Aquinas

I. Ibn Sina

On epistemology, Ibn Sina argued that the human mind can receive and catalog sense impressions and can
make  the  judgments  necessary  for  practical  action.  However,  the  highest  act  of  the  intellect  –-  that  of
abstracting universals from sense impressions of corresponding particulars –- is beyond the capacity of the
finite,  embodied  human  mind.  Instead,  following  a  cryptic  remark  by  Aristotle  in  his  book  on  the  human
soul,  De  Anima,  Ibn  Sina  thought  the  act  of  abstraction  occurs  when  the  individual  human  mind  is
illuminated  by  something  called  the  “Active”  or  “Agent  Intellect”.  Our  individual  minds  ibn  Sina  called
“possible” (meaning passive or receptive). The active intellect is a kind of cosmic intellect, emanating from
God,  that  comes  to  us  when  we  recognize  and  reason  by  means  of  universal  concepts.  We’ll  examine  the
problem of the relationship between the Active Intellect and the individual soul in the next section, when we
turn to ibn Rushd.

II. Ibn Rushd on The Agent Intellect

The  theory  of  the  active  or  “agent”  intellect  was  developed  in  response  to  three  ideas  from  Aristotle’s
philosophy of the mind:

1. That man, unlike all other animals, possesses a capacity for rational, scientific knowledge.
2.  The  presence  of  this  rational  capacity  cannot  be  explained  in  physical  or  biological  terms:  yet,  the
individual  human  soul  is  simply  the  actualization  of  the  human  body’s  biological  capacities.  Hence,
rationality must somehow enter the human soul from the outside.
3.  Rational  mind  is  immaterial  and  simple  and,  therefore,  naturally  indestructible.  Since  the  rational  mind
exists outside the individual human soul, the immortality of Mind does not guarantee the immortality of the
individual personality.

The crucial question that divides the al-falsafa philosophers is this: when the agent intellect illuminates the
individual human soul, does it give rise to an enduring individual intellect? Ibn Sina argues that it does, and,
on  this  basis,  he  affirmed  the  immortality  of  the  individual  human  soul.  Because  the  human  soul  is  lifted
from  the  merely  physical  and  biological  domain  by  the  illumination  of  the  Agent  Intellect,  the  individual
human  soul  shares  in  the  simplicity  and  immateriality,  and,  therefore,  in  the  immortality  and
indestructibility of the Agent Intellect.

In  contrast,  ibn  Rushd  argued  that,  throughout  the  process  of  illumination,  the  individual  soul  remains
entirely passive and receptive. It is the Agent Intellect that engages in all rational, scientific thinking in and
through the individual human being. This activity doesn’t engender any capacity for rational thought within
the individual human being. Consequently, when a human being dies, the soul dies with him or her, just as
the animal or plant “soul” dies along with the organism. (Ibn Rushd did, however, agree with the Koran that
there would be a resurrection of the body.)

III. Aquinas on Knowledge (Epistemology) and the Soul

A. What are we doing when we philosophize about knowledge?

There  are,  broadly  speaking,  two  ways  of  thinking  about  epistemology  (or  the  philosophy  of  knowledge).
We  could  think  of  it  as  primarily  concerned  with  skeptics  and  skepticism.  Skeptics  deny  that  we  know
anything. Some even deny that some opinions are more reasonable than others. One could take the task of
epistemology to be the refutation of skeptics: coming up with proofs that we do know some things, proofs
that are so powerful and undeniable that the skeptic will be forced to agree.

This is the way most “modern” philosophers (from the time of Rene Descartes in the 16

century until the

early or mid-20

century) did think about epistemology. In this respect, Augustine was something of a

“modern” philosopher, because he too tried to refute the skeptic by means of an argument very similar to

Descartes’s:  if  I  doubt  (as  the  skeptic  recommends),  then  at  least  I  know  that  I  doubt,  and  no  amount  of
further doubting can possibly deprive me of this certainty.

Descartes’s motivation for taking epistemology this way depends, I believe, on the fact that Descartes (and
other  16

century thinkers like Francis Bacon and Galileo) introduced a new distinction between

“philosophy”  and  “science”.  Science  was  concerned  with  the  description  and  explanation  of  physical
phenomena  by  means  of  mathematics  (especially  geometry).  Descartes  divided  reality  into  two  separate
components: souls and matter. Science tells us all there is to know about matter, and we can know all there is
to  know  about  our  souls  by  simple  introspection.  What  then,  is  left  for  “philosophy”  to  do?  Descartes’s
answer  was  this:  science  takes  certain  things  for  granted  (like  the  reliability  of  our  senses  and  of  our
mathematical judgments).  Science cannot defend itself against skeptics who think that all our sense data and
all our mathematical intuitions may be illusions. So, philosophy’s job is to refute the skeptic by arguments so
powerful that the skeptic simply cannot deny them. On this view, epistemology is a kind of super-science, a
science that must be completed before any other science can proceed with any confidence.

This  modern  epistemological  project  was,  in  my  judgment  and  in  the  judgment  of  most  (but  not  all)
contemporary philosophers, a total and catastrophic failure. Around the turn of the 19

and 20

centuries, a

number  of philosophers (including  G. E. Moore, Ludwig  Wittgenstein, and  the  American W. V.  O. Quine)
began to move back toward a more classical conception of epistemology, according to which epistemology is
just  one  part  of  our  knowledge  of  reality.  On  this  view,  epistemology  does  not  come  “before”  the  other
sciences or branches of philosophy, nor do they come entirely “before” epistemology. Instead (to use Oscar
Neurath’s metaphor), we are on a raft in the middle of an ocean, the various rafts representing the various
sciences and branches of philosophy at their current stage of development. It would be crazy to jump off the
raft and to try to build a new and better one from scratch in the middle of the ocean, which is in effect what
Descartes  and  his  modern  followers  tried  to  do.  Instead,  we  should  recognize  that  all  our  opinions  are
fallible and tentative, including those of epistemology.

Aquinas’s approach to epistemology is like that of Moore, Wittgenstein and Quine, and radically unlike that
of  Descartes  and  such  other  “modern”  philosophers  as  David  Hume  and  Immanuel  Kant  (of  the  18

century).  Aquinas  isn’t  concerned  with  refuting  the  skeptic.  He  takes  it  as  obvious  that  we  know  many
things: the job of philosophy is to explain how this is possible, to describe accurately the causes and nature of
human knowledge, not to prove beyond all doubt that it actually exists.

This means that Aquinas is free to use everything he knows about human beings and the world they inhabit,
whether the source of that knowledge be the senses, the Scriptures, common sense, or scientific discovery.
The sources don’t have to be absolutely indubitable before the epistemologists can legitimately use them as
data for this theorizing.

B. Human Knowledge vs. Angelic Knowledge

Whether or not angels actually exist, we can conceive of beings who know everything they know by direct
vision  of  the  truths  as  they  flow  from  God’s  essence  and  creative  will.  Such  angels  could  know  both
universal facts (like the laws of nature) and particular facts (e.g., of geography, history or biography) simply
by  knowing  what  kind  of  world  God  has  chosen  to  create.  They  wouldn’t  need  to  go  out  and  collect
information about these things, since they would fully understand their causes within God’s will.

Aquinas  takes  it  as  obvious  that  human  beings  (at  least,  this  side  of  death)  aren’t  at  all  like  that.  Our
intellectual powers are far weaker: we can’t grasp God’s nature, and we have no direct access to His will. We
need  information  from  another  source.  Fortunately,  we  do  have  such  a  source:  the  five  senses.  Following
Aristotle, Aquinas goes so far as to say that all of our understanding comes to us through the senses: apart
from  sensory  information,  our  intellect  is  a  “blank  slate”  (tabula  rasa).  However,  unlike  some  modern
“empiricists” (like David Hume), Aquinas did not think that our knowledge begins and ends with the senses.
Thanks to the information about particular things provided by the senses, we are able to rise eventually to
the knowledge of universal truths, such as the laws of mathematics, physics and metaphysics.

Aquinas’s epistemology is very much influenced by his attempted solution to the problem of universals. In
order  to  have  universal  knowledge,  we  must  have  knowledge  of  universals  (of  the  common  essences  and
natures  of  things).  However,  Aquinas  rejects  extreme  realism:  he  doesn’t  believe  that  the  universals  are

things in their own right, existing independently of particulars. In fact, as Abelard argued, universals as such
exist only in our minds (and those of other intellectual beings, like the angels). Following Philo, Augustine
and many others, Aquinas replaces Plato’s eternal Forms or Ideas with eternal types within the mind of God.
(How is this compatible with God’s absolute simplicity? That’s a tough problem.)

So, there are universals in God’s mind and ours (particular ideas that can be predicated of many things), and
otherwise  everything  is  particular.  Nonetheless,  things  come  with  “common  natures”,  the  essences-
considered-absolutely, which have a merely logical being, and which suffer from an extreme sort of logical
incompleteness (they are neither one nor many, neither universal nor particular, and so on).

How do these common natures move from their existence as particulars in the real world to an existence as
universals in our minds?  By the following two-step process:

1. The sensible (visible, tangible, smellable, tasteable, audible) object acts upon our sense organs, producing
an image (which Aquinas calls a “phantasm”) within our bodies. The image of a red thing needn’t itself be
red (anymore than the image of a sharp thing need be sharp, or the image of a cube be cubical): instead the
phantasm represents the characteristics of the external object.

These representations are normally accurate,

but can be distorted in various ways (by disease, malformation or abnormal environments).

2. The active intellect “sees” or “apprehends” these phantasms within its body and extracts or “abstracts” the
essence  (called  the  “intelligible  species”),  placing  this  intelligible  species  within  a  receptacle  called  the
“passive  intellect”.  The  intelligible  species  are  universals,  present  within  the  mind.  The  species  make  the
corresponding kind of thing into an object of knowledge: when we have the species man within our passive
intellect, we are enabled to understand what men are (i.e., the natures of the real, particular men).

Once we have universals within our minds, we can do two further things: we can make various judgments,
forming propositions that we accept as true; and we can engage in reasoning, inferring new truths from old
ones.  At this point, Aquinas comes closer to Augustine’s divine-illumination model: he says that we make
these judgments by means of an inner intellectual “light”, which we have by our participation in the divine,
uncreated  light  of  God.  We  are  able  to  make  mostly  reliable  judgments  because  God  has  made  us  in  His
image,  placing  within  us  a  kind  of  likeness  of  his  own  power  of  understanding.  However,  there  are  two
limitations imposed on us by our human nature: we depend on the senses to provide us with the intelligible
species,  and  we  also  depend  on  the  senses  to  provide  us  with  the  basis  for  making  judgments  about
particular things (like ‘Socrates is sitting’).

Aquinas makes very clear (in Q85, A2) that we know real, external things by means of the intelligible species
in our minds: we don’t only, or even primarily or in the first instance, know the species within our minds.
That is, I know what men are by virtue of having the intelligible species of man within my mind.  I may have,
however,  no  idea  that  such  a  thing  as  an  intelligible  species  exists  at  all.  It  is  only  through  philosophical
thought  and  reflection  that  I  come  to  recognize  that  my  mind  actually  contains  such  things.  The  first  and
primary object of my knowledge is the “external world”, the world of sensible objects. In this way, Aquinas
avoid the slide into “idealism” that was so typical of philosophers in the 16

through 19

centuries. Idealists

think that all I can know for sure are the contents of my own mind. I have to make guesses (perhaps wild,
unsubstantiated guesses) about whether anything really exists outside my mind that these ideas represent.
For Aquinas, this is all backward. I wouldn’t even know that I had a mind or any ideas within it if I didn’t
first know many things about the real, external world by means of my five senses.

The two step-process mentioned above is Aquinas’s sketch of how it is possible for human knowledge to get
started.  The  sketch  makes  it  sound  as  though  acquiring  understanding  is  very  simple:  just  look  around,
gather  some  sense  experience,  and  –-  Swoosh!  –-  your  active  intellect  will  swoop  down  and  extract  some
universals. In other words, we might take Aquinas as giving us a simple, two-step recipe for discovering the
true essences of things: 1. Observe. 2. Think.

There is some difference in interpretation on this point, but I agree with Norman Kretzmann in thinking that the most

reasonable interpretation does not require the sensible species to have in reality the form it represents. See his paper on
Aquinas’s philosophy of mind in the Cambridge Companion to Aquinas.

In  fact,  Aquinas  does  indeed  recommend  these  two  activities,  and  in  doing  so,  he  is  providing  genuine
science  with  its  proper  foundation.  Many  philosophers  have  recommended  that  we  limit  ourselves  to  just
observing  without  thinking  or  just  thinking  without  observing,  or,  indeed,  to  do  neither.  Nonetheless,
Aquinas  was  under  no  illusions  about  how  difficult  it  is  to  discover  the  true  essence  of  a  thing.  He  said,
famously, that no philosopher had yet understood anything so simple as a fly. (We now have some idea how
true this was.)  You can stare at water all day, drink it and swim in it even, and your active intellect won’t
just pull H

O out of your experience with no further ado. Aquinas recognized that, before the active intellect

can  act,  we  must  accumulate  enough  experience,  and  experience  of  the  right  kind.  It  takes  investigation,
experimentation,  collation  and  comparison,  and  many  other  activities  before  we  can  be  in  a  position  to
abstract fully the essence of a sensible thing.

Aquinas  insists  that  scientific  knowledge  is  a  possibility,  given  the  right  combination  of  experience  and
analysis. In this respect, he is on the side of science (physics, chemistry and so on) and against those skeptics
who undermine the confidence needed to pursue the “dream of a final theory” (as our own Steven Weinberg
puts it).