Introduction to Philosophy
Lecture 4
Thomas Aquinas & an Intro to
Philosophy of Religion
By David Kelsey
Aquinas
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Saint Thomas Aquinas
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Lived from 1225-1274.
A monk whose writings have been deemed authoritative by the Catholic Church.
In 1244 became a friar. Later he became a priest and in 1323 was made a Saint.
Heavily influenced by the works of Aristotle.
In his work Summa Theologica he gave 5 different argument’s for God’s existence.
He called these the 5 ways.
Aquinas on Aristotle
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Aquinas on Aristotle:
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Aquinas was greatly influenced by the works of Aristotle.
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But Aquinas thinks there is a fundamental mistake in Aristotle’s metaphysics.
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Aquinas thinks Aristotle overlooks the notion of existence.
Aristotle on existence:
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Form is what actualizes a potentiality, matter, into an actually existing thing.
And efficient causes are what bring a particular substance into being.
But the world, existing eternally, has no efficient cause. Existence is just born in its form.
Aquinas on existence
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So for Aristotle, Form brings existence along with it. But for Aquinas, a things existence
differs from its essence.
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The essence of any substance is both matter and form for such an object is different from something
purely formal…
For something imaginary like a phoenix, its essence being form and matter, it lacks existence.
So existence is something added to those substances that do in fact exist.
Likewise for spiritual substances, they are composed of pure form and existence.
It is this new understanding of existence which leads Aquinas to rethink Aristotle’s notion of
efficient causation and subsequently God’s existence as unmoved mover.
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We now turn to Aquinas’ famous 5 ways…
Theism
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There are 3 general argument patterns for Theism.
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We have so far seen one of these argument patterns: the Ontological argument.
Ontological Arguments:
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Argue that by an analysis of the very concept of God he must exist.
Cosmological Arguments:
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Theism, Atheism & Agnosticism
The form of the argument is roughly this:
• There must be a first cause of all things and this first cause must be God.
Teleological Arguments:
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Argue for God’s existence via premises about the design or goals or purposes of
things.
The 5 ways
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The 5 ways:
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The first way: about things causing change in other things.
The second way: about ‘efficient causation
The third way: about things causing others to exist
The fourth way: about things causing others to be good or noble.
The final way: about purposes.
Aquinas’ 5 ways
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The first 4 ways:
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Different versions of the Cosmological argument.
Each way uses a different sense of the word ‘cause’.
In each case Aquinas wants to show that there is an uncaused cause…
– All Cosmological arguments have a form like this:
• 1. There is something that causes everything else, I.e. a first cause.
• 2. Only God could be a first cause.
• 3. Thus, there is a God.
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The final way: a version of the teleological argument.
The first way
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The form of the first way:
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1) Things change.
2) Change is an alteration in which something becomes actually what it was only
potentially until then.
3) Everything that changes must be made to change by another thing.
4) But if one thing causes change in another, either the cause is a first cause of change
or it is caused to change by another (from 3)
5) There couldn’t be an open causal chain of changing changers going back forever
into the past.
6) Thus, there is an unchanging changer, a first cause of change. (from 1 & 5)
7) And this first cause is God.
Aquinas’ argument for the 3rd premise
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The third premise: 3) Everything that changes must be changed by
another thing.
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A change from potentiality to actuality can only be brought about by something that is
already actual.
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The ball and batter…
Nothing can be both potential and actual in the same respect.
So nothing can change itself.
Thoughts on this argument? Can you think of anything that could change itself?
Aquinas’ argument for the 5th premise
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The 5th premise: There couldn’t be an open causal chain of changing changers
going back forever into the past.
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In this case there is no first cause of change
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Open causal chain: an infinite number of things, one causing change in the other…
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But then there couldn’t be any intermediate causes either
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Ball and Batter…
Such causes could only cause change if actualized themselves by some prior cause.
Ball and Batter again…
But if there weren’t any intermediate changers there would be no change at all.
Thoughts on this argument?
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Is it possible that we have intermediate causes of change without a first cause?
Maybe there is another possibility: a closed loop of intermediate changers…
Evaluating the first way
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The first premise:
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The fourth premise:
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Assuming that everything that changes must be changed by another thing, if one thing
causes change in another, either the cause is a first cause of change or it is caused to
change by another.
The fifth premise:
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says simply that things change.
Change: Aquinas means the kind of change we see in the ball when it is hit by the bat.
There is an unchanging changer, a first cause of change.
This thing isn’t changed by anything else. It can cause change though.
Domino’s…
Question: why suppose that there is just one unchanging changer?
The conclusion:
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This first cause is God
Question: why suppose this first cause is God?
The Second Way
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The Second way:
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1) efficient causes come in series
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2) Such series of efficient causes could not go on to infinity
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Something cannot be the efficient cause of itself for to be so it would have to preexist itself,
which is not possible.
And if you take away a cause you take away its effect
If the series were infinite there would be no first cause.
If there were no first cause there would be no intermediate causes...
3) So there must be a first efficient cause
4) this everyone gives the name God
Evaluating the Second way
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Challenging the Second way:
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Some things to notice:
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Notice the similarity between the first and second ways…
The second way is focused on a specific kind of causation, efficient causation.
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An efficient cause causes something to come to be
Example: the hammer, the spark and the explosion
Evaluating the premises:
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Premise 1
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Premise 2
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Questions?
Premise 3
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Questions?
Questions?
The conclusion:
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Questions?
The Third Way
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Two ways in which a thing can exist:
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Necessary things can’t fail to exist.
Contingent things come into and go out of existence.
The third way:
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1. Some things must exist of necessity.
2. There can’t be an open causal chain of necessary things each causing the next to be
necessary.
3. Thus, something must be ‘necessary per se’.
4, And this is God.
The first premise
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The first premise:
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Says that something must be necessary.
So not everything can be contingent.
His argument:
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1) consider if everything existed contingently.
2) All contingent things must start to exist at some time.
3) So all contingent things must fail to exist at some time. (from 2)
4) But then there must have been a time at which nothing existed. (from 1 & 3)
5) But if there had been such a time nothing would exist now.
• From nothing you get nothing
6) But things do exist now.
7) Something must exist of necessity. This thing caused contingent things to come to
be.
Finishing the 3rd way
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The second premise:
– says that there cannot be an open causal chain of necessary things each causing the
next to be necessary.
– His argument:
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Question?
The third premise:
– says that something must be ‘necessary per se’
– Necessary Per Se:
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In this case there is no first cause of change.
But then there couldn’t be any intermediate causes and so no change at all…
Something that owes it’s necessity to nothing else
it can cause the necessity of other things though.
Question?
The conclusion:
– Questions?
The Fourth Way
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The fourth way:
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1) Some things are good (noble and true).
2) Some things are better (or more noble or truer) than other things.
3) These better (more noble and truer) things have more good (are more noble and are
truer) in accord with their distance from a maximum.
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4) if something that is maximally true, good and noble were not in existence then there
would be no things possessing truth, goodness and nobility to a lesser degree.
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Comparative judgments…
So whatever is maximally good (noble and true) is the cause of whatever else that is good
5) Thus, something is maximally good and causes everything else that is good (from 1
& 4)
6) This maximally good thing we call GOD.
Finishing the argument
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Something to notice:
– Notice the appeal that this argument makes to the great chain of being…
The first 3 premises:
The fourth premise:
– Question: This seems to imply that the maximally good thing is the cause of
whatever else is good.
– Questions?
Premise 5:
The conclusion:
The Fifth Way:
the argument from design
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The argument from design:
– 1. A machine is the effect of intelligence
• For every clock…
– 2. The world is like a machine
• It is an ordered whole. Newtonian mechanics tells us so.
• So the world is like a clock…
– 3. Thus, the world is the effect of some intelligence
– An argument a posteriori:
• it is an argument that depends upon experience and matters of fact…
– An argument by analogy:
• Since worlds are like machines and machines have designers so too does the
world have a designer.
– A causal argument:
• The first premise and conclusion…
Critiquing the Argument from design
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Critiquing the argument from design:
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Note: These criticisms are taken from David Hume’s Dialogues on Natural Religion…
1. A posteriori arguments are never valid and can never entail their conclusions. Thus,
the most the argument from design can give us is probability…
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2. Causal arguments follow this principle: the cause must be proportioned to the effect.
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“If the cause be known only by the effect, we never ought to ascribe to it any qualities, beyond
what are precisely requisite to produce the effect.” (Enquiry, 190)
But if you look around the world it certainly isn’t perfectly good, intelligent or wise. It seems to
have none of the qualities we attribute to God and so cannot prove the existence of a perfect
God…
The third response to the design argument
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Taking the analogy seriously: The analogy is between machines and their designers and the
universe and its designer.
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Many people often cooperate to make a machine  Many Gods
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Wicked people can create technological marvels  a wicked God
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Machines are made by mortals  a Mortal God
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The best machines are a result of a long history of gradual improvements.
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But then “Many worlds might have been botched and bungled, throughout an eternity, ere this system was struck
out; much labor lost; many fruitless trials made; and a slow but continued improvement carried on during infinite
ages in the art of world-making.” (Dialogues, 36)
What Hume shows us here is that any of these is possible.
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And we have no way of knowing which are the similarities between worlds and machines and which are not.
The final response to the
design argument
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The final response:
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There is one respect in which the universe is entirely unlike machines
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The universe is “entirely singular”
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We can infer the cause of a machine because we have in the past experienced the
constant conjunction of machines and designers.
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But if we apply this reasoning to the universe, we would need past experience of the
making of worlds, such that worlds are constantly conjoined to designers. And yet…