Philosophical Arguments for God’s
Existence
Prof. Rob Koons
robkoons@yahoo.com
robkoons.net (Unpublished Papers)
Leadership for America 2013
Can we “prove” that God
exists?
•
•
Much depends on what we mean by “prove”.
We can’t prove God’s existence in the way
that one can “prove” a theorem of
mathematics, like the Pythagorean theorem
or the existence of infinitely many prime
numbers – by pure logic from axioms
everyone accepts.
God and Natural Reason
• However, we can know by natural reason (and not
only by faith) that there is a God. This knowledge
is available to anyone with fully functioning rational
faculties. However, these faculties can be
damaged by sin (both individual and societal).
• To know God’s existence, we must be willing to
follow reason to its utmost limit.
Doubt can be Healthy or Unhealthy
•
•
•
A healthy doubt enables us to think more
clearly and responsibly, by protecting us
from irrational fads, myths and fables.
A healthy doubt promotes a prudent
humility and openness to new
information.
However, doubt, when carried to
extremes, actually paralyzes thought,
making us doubt those first principles
without which all knowledge would be
impossible.
The Error of the
“Enlightenment”
•
•
The “Enlightenment”, beginning with the French
philosopher and mathematician René Descartes (15961650) and the British philosopher John Locke (16321704), created the Myth of the Method.
According to this Myth, all human reasoning can be
reduced to a mechanical recipe, a set of procedures that
all can follow to reach the right conclusions, without the
need of exercising judgment or wisdom.
Post-Modernism: The Overreaction
•
•
The Enlightenment idea experienced a
series of catastrophic refutations in the 19th
and 20th centuries, as philosophical
rationalism failed to produce the universal
consensus that the Enlightenment had
promised.
In modern times, post-modernism has
arisen as a natural reaction to this failure:
denying the very existence of human
reason or of a universal Truth (with a
capital T), as opposed to “my truth” or
“our truth”.
The Post-Modern Mindset
• Post-modernists are suspicious of any claim to
have or to know any universal truth.
• They tend to see the use of logic,
argumentation, or reasoning as a form of
coercion or aggression.
• “Tolerance” becomes the only virtue.
Post-Modernists are Inconsistent
•
•
•
However, no one can really live as PostModernists claim.
Post-Modernists believe that they do
possess a universal truth: the truth that
there is no universal truth.
Post-Modernists are intolerant of those
who do not practice post-modern
‘tolerance’.
So, What to do?
•
•
Realize that the Post-Modernists are wrong
about everything, including postmodernists.
All human beings have a natural aptitude
for Truth, and the human mind has a
fundamentally rational structure that cannot
be erased.
Proving God’s Existence
• What follows will be based on Ways 1-3 of St.
Thomas Aquinas’s Summa Theologica I 2 a3, and
his much longer Summa Contra Gentiles:
– http://www.newadvent.org/summa
– http://www2.nd.edu/Departments/Maritain/etext/gc.ht
m
• By Alexander Pruss, at Baylor: The Principle of
Sufficient Reason (Cambridge Univ. Press, 2010).
• Also, some of my own work, including my chapter
in Oxford Studies in the Philosophy of Religion,
vol. 1, ed. Jonathan Kvanvig, 2008, and “A New
Kalam Argument”, Noûs 2012 (forthcoming).
An Argument with a Long History
•
Accepted by philosophers from six great
traditions:
–
–
–
–
–
–
•
Ancient pagan (Greek and Roman)
Jewish
Christian
Moslem
Indian (10th century Nyaya school)
Early modern European
Developed over 2500 years.
Endorsed by many philosophers
•
•
•
•
•
Plato and Aristotle, Plotinus
Maimonides, al-Farabi, Avicenna, Averroes,
Udayana
St. Thomas Aquinas, John Duns Scotus
Rene Descartes, Gottfried Leibniz, John
Locke.
Frederick Copleston, Mortimer Adler, Etienne
Gilson, Richard Taylor, Austin Farrer, Richard
Swinburne, Timothy O’Connor, Alexander
Pruss
What do we know?
•
•
•
Hold out your right hand, and
spread out your fingers.
Do you know that there is a
hand with five fingers in front
of you?
If so, you can also know that
God exists
Empirical Knowledge
•
Your knowledge of your hand and its
fingers is a case of ‘empirical
knowledge’:
– Things we know by observation (using the
five senses)
– Things we know by memory (remembering
what we have observed)
– Things we know by the testimony of others
– Things we can infer from these by scientific
or historical reasoning
Empirical Knowledge Depends on
“Causality” (Cause and Effect)
•
When we know something empirically, our
belief is linked by a chain of cause and effect
to the thing we know.
– Sensory perception involves a chain of cause and
effect (e.g., light reflection, retinal stimulation)
– Memory involves a chain of causes in the brain,
recording and recalling a memory trace
– Testimony is passed down a chain of
communication events
– Scientific and historical reasoning infers causes
from effects or effects from causes.
Causal Chain
If any of these steps could occur
without a cause, knowledge
would be impossible.
Does everything have a cause?
•
•
•
•
Everything involved in empirical knowledge
must have a cause.
Suppose, for example, that sensations could
occur without any cause whatsoever.
If that were ever possible, it would be possible
all the time, and with a completely
unpredictable and inscrutable probability.
We would have good reason to think that we
might be “Boltzmann brains” right now – with
nothing but illusory sensations.
Universal Causality must be
Self-Evident
•
•
•
We supposed that we did have some empirical
knowledge (remember the five fingers).
But such knowledge is impossible unless we
know that every step involved (before the last
one) necessarily has a cause.
We can’t know that empirically (without vicious
circularity), so it must be a self-evident
principle of reason. To doubt this is the
unhealthy kind of doubt.
Evidentially Proximate vs. Ultimate
•
•
•
There is one sort of thing that could fail to
be caused, without threatening empirical
knowledge: “ultimate” things.
Something is “ultimate” just in case it is
obviously and certainly the kind of thing
that could not possibly be evidence for
anything else.
Not just uncaused but self-evidently
uncausable.
The Universal Causation Principle
•
•
Let’s say that something is ‘natural’ just
in case it isn’t ultimate.
Reason tells us, with certainty:
 Every natural thing must
have a cause.
Does Absolutely Everything have a
Cause?
•
•
If absolutely everything had a cause, then
the network of causation would have to
contain either (i) loops (things that
caused themselves) or (ii) infinite
regresses.
However, nothing can cause itself, since
it would have to both exist (in order to be
the cause) and not exist (in order to be a
potential effect) at the same time.
Death to
Fred!
The Grim Reaper
Jose
Benardete’s
Infinity: An Essay
in Metaphysics
(1964)
Death to
Fred!
Death to Fred!
12:00:15
12:00:07.5
12:00:03.75
12:00:01.875
12:00:30
12:01
The Unbounded Version
•1 B.C.: GR #1
•2 B.C: GR #2
•3 B.C.: GR #3
etc.
Each Grim Reaper issues a death warrant
for Fred if and only if no preceding GR has
done so.
(Invented by Prof. Pruss at Baylor, 2009.)
Story leads to a Contradiction
•
•
•
At least one GR has initiated a death
warrant, since otherwise all would have
failed to do their duty. Say it was GR #n
GR #n would have acted only if all earlier
GR’s did not act. So, both GR #(n+1)
and GR#(n+2) did not act.
But, if GR#(n+2) and all earlier GRs did
not act, then GR#(n+1) would have
acted. Contradiction.
Reductio ad Absurdum
•
•
•
If a contradiction follows logically from a
proposition, then that proposition must be
false.
The GR story follows from the proposition
that an infinite regress is possible, and
the GR story is self-contradictory.
Therefore, an infinite causal regress must
be impossible.
Another argument for a First Cause
•
•
•
Even if infinite regresses were possible, they
would have to have a cause as well. The
Gale-Pruss cannonball argument.
Let the Cosmos = the sum of all variable,
contingent facts. The Cosmos will itself be
contingent, so it comes under the Universal
Causal Principle.
The cause of the Cosmos must be separate
from it – and so must be infinite and
necessary. (This argument is from al-Farabi,
Duns Scotus, and Gottfried Leibniz)
Existence of a First Cause
• If the network of causation contains no loops and
no infinite regresses, then there must exist at least
one uncaused or “First” cause.
• However, we have seen that empirical knowledge
requires that every natural thing must be caused.
• So, any First Cause must be “ultimate”: obviously
(self-evidently) incapable of being evidence for
anything else, i.e., uncausable.
What must Ultimate things be like?
• What characterizes all the natural things?
(Things we perceive or remember, things that
are intermediate between perceptions and
objects, things that can be used as scientific
data)
• They are all (obviously) variable, inconstant,
changing.
• So, an ultimate thing (a First Cause) must be
invariant, constant, unchangeable.
Nature of the First Cause
From First Cause to Absolute Being
•
•
•
In order to be uncaused, the First Cause
must be necessary (constant and
invariant).
In order to be necessary, the FC must be
infinite in every respect, because what is
finite is variable.
In order to be necessary in itself, the FC
must be simple or absolute Existence,
since if it were not, it would be limited or
bounded in some way, and so finite.
From Absolute Being to One God
•
•
•
There could be only one thing that is
identical to Absolute Existence, because if
there were two, they’d be identical to each
other.
This being must have all possible power,
since it must be the cause of all possible
beings.
In order to have all possible power, it would
have to possess all positive attributes to their
absolute maximum degree: perfect
knowledge, beauty, wisdom, goodness, etc.
To Summarize
•
•
•
•
•
•
If uncaused, then ultimate.
If ultimate, then self-evidently uncausable
(“SU”).
If SU, then unbounded, unconstrained
and unlimited in every respect (“UUU”).
If UUU, then identical to pure existence
(“IPE”).
IF IPE, then one and perfect.
If one and perfect, then God.
Some Limitations of the Argument
• We know that the First Cause is infinite and has
every purely positive ‘perfection’.
• We know a lot of negative things about the FC:
immaterial, timeless, unbounded.
• However, the argument doesn’t show that the FC is
personal (wise, knowledgeable, just, loving) – since
it isn’t obvious that those qualities are purely
positive.
• Even if God were perfectly powerful and
knowledgeable, it wouldn’t follow that He was
omnipotent or omniscient (capable of doing and
knowing absolutely everything).
The One-Two Punch
•
To summarize this lecture and the two
arguments on design (fine-tuning and biology),
we have a convergence of arguments for the
conclusion that the universe has a
supernatural cause:
– From physics – the Big Bang and fine tuning.
– From metaphysics – the First Cause arguments.
•
The two together are much stronger than
either separately. Physics makes God’s
existence probable, metaphysics makes it
certain.
William Paley’s Design
Argument (By Analogy)
St. Thomas’s Cosmological Design
Argument (5th Way)
Advantages of the Latter
•
•
•
Avoids the infinite regress objection of
skeptics like Dawkins: “Who made
God?”
Starts with a cause of the Cosmos:
uses design only to establish and
confirm God’s intelligence.
Supplies crucial facts about God:
eternal, immaterial, infinite, wholly
good
Answering some objections
•
Necessary existence is impossible.
– The argument establishes that it is
actual, and so possible.
• Quantum Mechanics teaches that some
events are uncaused
– No -- it teaches that some events are
caused but not pre-determined in every
respect.
Hume’s Objection
•
•
•
•
God cannot exist necessarily.
What we can imagine existing, we
can imagine not existing.
What we can imagine is possible.
So, if God’s existence is possible,
so is His non-existence.
Replies
•
•
Not everything we can imagine is
really possible (time travel, infinite
regresses).
We cannot imagine God’s existing or
not existing: God’s being is beyond
our comprehension. However, we
can know that He exists (by the First
Cause argument).
Kant’s objection
•
•
•
•
The first cause argument supposes that God’s
existence is necessary.
To be absolutely necessary, God would have
to exist by definition.
However, nothing can exist by definition.
Suppose, for example, that I defined a
‘schmountain’ as a golden mountain that
exists.
We cannot conclude that schmountains exist
by definition, since that would entail that gold
mountains exist.
Reply
•
•
We are not saying that God exists by
definition – just that He is uncausable
by definition. Golden mountains are not
uncausable. We conclude that God
exists by argument, not by definition.
If such a God exists, He exists by virtue
of His own nature. Only an infinite and
simple being could exist in this way.
Why believe the principle of causality?
Perhaps it [the principle of causality] just expresses an
arbitrary demand; it may be intellectually satisfying to
believe that there is, objectively, an explanation for
everything together, even if we can only guess what the
explanation might be. But we have no right to assume that
the universe will comply with our intellectual preferences.
J. L. Mackie, The Miracle of Theism: Arguments for and
against the Existence of God (Clarendon Press, Oxford,
1982), p. 86.
Is the Argument Self-Contradictory?
...the causal argument is not merely valid but selfcontradictory: the conclusion, which says that something
(God) does not have a cause, contradicts the premise,
which says that everything does have a cause.
John Hospers, An Introduction to Philosophical Analysis,
2nd edition (Prentice-Hall, Englewood Cliffs, NJ, 1967), p.
431.
Objection: Why Can’t Matter be
Ultimate?
Aquinas’s implicit assumption is that anything whose
essence does not involve existence must, even if it is
permanent, depend for its existence on something else...
we have no reason for accepting this implicit assumption.
Why, for example, might not there be a permanent stock of
matter whose essence did not involve existence but which
did not derive its existence from anything else?
J. L. Mackie, The Miracle of Theism: Arguments for and
Against the Existence of God (Clarendon Press, Oxford,
1982), p. 91.
Couldn’t the Universe itself be a First
Cause?
•
•
•
•
No – the universe is merely an aggregate
of things, each of which is variable and
contingent.
What about the Big Bang?
We know that it is finite in many
dimensions (the fine-tuned constants,
entropy, velocity).
It isn’t ultimate: it isn’t obviously
uncausable. God is – by definition.
Objection: Why stop with God?
All three of these arguments (Aquinas’s first three ways) rely upon the idea of a
regress and invoke God to terminate it. They make the entirely unwarranted
assumption that God himself is immune to the regress. Even if we allow the
dubious luxury of arbitrarily conjuring up a terminator to an infinite regress and
giving it a name, simply because we need one, there is absolutely no reason to
endow that terminator with any of the properties normally ascribed to God:
omnipotence, omniscience, goodness, creativity of design... Richard Dawkins,
The God Delusion, Houghton Mifflin, Boston, 2006, p. 77
But the greatest weakness of this otherwise attractive argument is that some
reason is required for making God the one exception to the supposed need for
something else to depend on: why should God, rather than anything else, be
taken as the only satisfactory termination of the regress? If we do not simply
accept this as sheer mystery..., we shall have to defend it in something like the
ways that the metaphysicians have suggested. J. L. Mackie, The Miracle of
Theism: Arguments for and Against the Existence of God, 1982, p. 92.
Can God be Ultimate (SelfExplanatory)?
It is utterly impossible for God to be self-explanatory, Theists usually
consider God's existence to be part of His essence and maintain that
this renders God self-explanatory. But what do we mean by a certain
characteristic’s being part of the essence of a thing? The essence of a
thing is what it is. The essence of a table, for example, is whatever is
common to all particular instances of tables. Having a flat surface on
top is a characteristic which is part of the essence of a table. But the
fact that anything that is a table must have a flat surface does not
explain why this particular thing was constructed as a table -- that is,
why it is a table. It merely explains why the thing must have a flat
surface if it is a table. Similarly the fact that God has an essence which
includes existence would not explain why God is a being which has this
particular essence. It only explains why he must exist if he has the
particular essence he happens to have.
B. C. Johnson, The Atheist Debater’s Handbook (Prometheus Books,
NY, 1983), p. 66.
Is God utterly Unknowable?
Despite the complicated maneuvers of Christian
theologians to escape from agnosticism, despite the
abstract dissertations and impressive sounding attributes of
God, it always comes down to this: the nature of God is
“entirely unknown” to man. The characteristic under
consideration -- the identity of God's essence and
existence -- is nothing more than an extremely complicated
way of conceding the very point which we are attempting to
prove: that the very concept of God is without cognitive
content. The Christian cannot give substance and meaning
to the term “God”; it is a blank, an unknown “something”.
George H. Smith, Atheism: The Case Against God
(Prometheus Press, NY, 1989), p. 66.