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St. Thomas Aquinas (1225-1274)
• Youngest son of wealthy merchant who joined the
Dominicans against the wishes of his parents
• One of first philosophers/theologians to take seriously
Aristotle and Islamic Philosophy
• Represents the apex of the Medieval mind and achieved
the pinnacle of the Medieval project
• An extraordinary man:
• Brilliant
• Prolific writer
• Desired knowledge above all else . . .
• Great Saint
• Stopped writing in 1273; “It’s all straw”
• Died in 1274 and canonized in 1323
• Recognized as a Doctor of the Church
What is a reliable printed source?
Reliable when:
Story fits with personal
experience (it’s likely)
Names the author, who is an
authority
Right in the past about related
material
Other credible sources believe
it; often quoted
Not meant to entertain alone,
but to instruct or inform
The Bible:
Relates with personal
experience (human condition)
Moses, David, the Prophets
and the Apostles were all eyewitnesses
Many predictions right;
definitely filled with sound
psychological and ethical
advice
Believed by countless
numbers, including some of
the world’s smartest people
Clearly meant to instruct and
inform (and entertain . . . )
So, do you believe the Bible? Does everyone? Does everyone believe in reason?
What is the relationship between faith and reason?
I.1.1: Is philosophy all that is needed to reach our end (happiness)?
Theology
Philosophy
End (Happiness is
being with God)
Humans
Reason can make many things clear, such as
the truth about math, the natural sciences,
what is good, how to be virtuous . . .
But some things discovered by reason (such as things
about God), would be hard for everyone to understand by
reason alone, and even then it may be filled with error.
So, . . . What is needed in addition to Philosophy?
I.1.2: Is Sacred Doctrine actually a science?
Questions: What is a science? What makes a science true?
Assumed: Every science either begins in self-evident principles (e.g.: the law of
non-contradiction; the whole is greater than its parts; rocks always fall?; Rocks are
not alive?) or begins in the conclusions of another science (optics depends upon
principles discovered and supported by geometry; music depends upon principles
discovered and supported by arithmetic).
What kind of science is Physics? Biology? Psychology? Philosophy?
Is theology based upon self-evident principles or upon something else?
What is that something else?
Will everyone accept revelation as true? That is, will everyone accept what the
Bible says is true? (e.g., that God exists; God created the world; God is eternal).
What science also reaches some of those same conclusions?
Will everyone accept the conclusions of philosophy?
What if only valid deductive arguments are given and all the premises are true?
I.1.4: Is Theology a speculative or a practical science?
Theology is both (but its mostly speculative)
I.1.5: Is Theology the best (most noble) science?
The best speculative science is:
1) Most certain (foundation is certain)
2) Studies the most important subject
(that which has greatest worth)
The best practical science is:
1) Concerned with the highest purpose
Theology starts with God’s
revelation – can’t be wrong. Human
reason is often wrong.
Theology studies things that
transcend human reason. What can
be more worthy than that?
Theology has the greatest purpose
in mind – eternal bliss. What is
more important than that?
Does theology depend upon philosophy and the other sciences? If so, in what way?
Does this dependence ‘cheapen’’ theology?
I.1.6: Is theology the same thing as wisdom?
Yes . . . But the real interesting idea in this article is that ‘lesser matters should
be judged in the light of some higher principle.’
So, who has the right to judge another . . .
The architect or the day laborer?
The doctor or the patient?
The theologian or the philosopher? The physicist? The biologist?
Given this principle, is Aquinas correct when he writes in Objection 2:
The principles of other sciences either are evident and cannot be proved, or are
proved by natural reason through some other science. But the knowledge
proper to this science comes through revelation and not through natural reason.
Therefore it has no concern to prove the principles of other sciences, but only to
judge of them. Whatsoever
Whatsoeverisisfound
foundinin
other
other
sciences
sciences
contrary
contrary
to any
to any
truthtruth
of this
of this science
science
must bemust
condemned
be condemned
as false. as false.
I.1.8: Is theology really something that can be argued?
Yes, if your opponent believes at least some of theology’s starting principles –
which are revealed through revelation.
However, Aquinas writes: If our opponent believes nothing of divine
revelation, there is no longer any means of proving the articles of faith by
reasoning.
So, how can a theologian prove something about God to someone who doesn’t
believe in what the Bible reveals?
If theology is the ‘queen of the sciences’ why does theology need to
make use of philosophy?
Which has the greater role in theology – arguments from philosophers or
arguments from scripture? Why?
ST I.2.1: Is the existence of God self-evident?
When is a proposition self-evident?
Any proposition is self-evident when the predicate is included in the essence of the
subject. This basically means that the predicate is saying the same thing as the
subject. Can you think of an example?
Man is an animal.
Why is this self-evident?
What are the two types of self-evident propositions? What are examples of each?
A proposition is self-evident in itself and to us if everyone knows it – like the
difference between being and non-being or the whole and the parts.
A proposition is self-evident in itself but not to us when the predicate is included in
the subject, but this fact is not know to all people but only to the learned. For
example, ‘an incorporeal object does not take up space.’
How about this one . . . ‘God exists.’ Is this self-evident?
ST I.2.2: Can God’s existence be demonstrated?
Yes!
What do you think of the following quotation: "The invisible things of Him are
clearly seen, being understood by the things that are made" (Rm. 1:20). What
does it mean if true?
What are the two ways something can be demonstrated?
1) Through the cause (a priori). In this situation you argue from what is known
absolutely (the cause to its effects).
Ex: if you have Lou Gerigh’s Disease (ALS), you will gradually lose
muscular control of your extremities (hand and feet), then your limbs,
and finally your ability to speak and swallow.
2) Through the effect (a posteriori). In this situation you argue from what is
known prior to us (the effects to the cause).
Ex: if you gradually lost muscular control of your extremities, then limbs,
and you are finding it hard to speak or swallow, you have Lou Gerigh’s
Disease.
How do you prove the existence of atoms, protons and neutrons?
How do you prove the former existence of your great-grandfather?
How do you prove the actual existence of the love your parents have for you?
ST. I.2.3: Does God exist?
YES!
But don’t forget some of the points that were made before . . .
Many of the claims of revelation can be demonstrated by human reason (I.1.8)
Self-evident principles exist; however some are not known
to be true unless you study them carefully (I.2.1)
Everyone has some vague idea
of God, even if it is only dimly
understood (I.2.1.reply 1)
We can know that God exists because
we know his effects (I.2.1 and I.3.2)
The names given to God are understood through his effects (I.2.2.reply 2)
In general, each of the Five Ways essentially depends upon the same a
posteriori argument:
(P1) If there is no God, then the effects that only God could produce
would not exist.
(P2) The effects that only God could produce do exist.
(C) Therefore, God exists.
This argument is a modus tolens (MT), which is a valid logical form.
Remember, the definition of a valid argument: if the premises are true the
conclusion also has to be true.
So, if Aquinas can prove P1 and P2 are true, then any rational person must
accept the conclusion, that God exists.
So, are the premises true? How do you know?
Aquinas claims that P1 is true because it is both self-evident and it is
supported by reason, for if some particular cause does not exist then the
unique effect(s) that follow from that particular cause cannot exist.
Aquinas claims that experience (our senses) prove that P2 is true.
So, God exists.
In particular, Aquinas’ arguments depend upon the following points:
1. The Law of Non-Contradiction never fails. The LNC affirms that two
mutually contradictory properties cannot exist at the same time (e.g., it
cannot be true that there is a first cause and that there is not a first cause.)
2. Empirical Data (e.g., that motion and causality exist).
3. Several other self-evident principles (e.g., ‘whatever is in motion is put in
motion by something else in motion’, ‘there cannot be in infinite regression
of motion’, or ‘nothing can cause itself to be’).
So, given the law of non-contradiction, there are only two possibilities:
A) God does not exist
B) God exists
Given (2) the empirical data and (3) the self-evident principle, the
conclusion (A) that God does not exist is impossible.
Thus, the only logical answer is that God exists.
The argument from Motion (the First Way):
1) The cosmos is in motion (known by sense experience)
2) Whatever is in motion is put in motion by another (nothing can move itself)
a) Motion is the reduction from potency to act (known by definition)
ex. Fire makes wood (potentially hot) into a bonfire (actually hot)
b) The same thing cannot be both actual and potential in the same way
ex. What is actually hot cannot also be potentially hot in the same way
c) Therefore, nothing can move itself (follows from 2a and 2b)
3) There is no infinite regression of motion – for if an infinite regression were
possible there would be no first mover and hence no other movers either
ex. If there was no hand to move the staff, the staff would not move
Therefore, an Unmoved Mover – something that sets all things in motion but is
not moved itself – must exist. This must be so or there would be no motion –
which is absurd.
This unmoved mover is what we call God.
Can you explain any of the remaining 5 Ways?:
What is the empirical data?
What is the self-evident principle?
Does the argument work?