# Week 3 Notes

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8 Feb 2011
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Philosophy Notes
Lecture Week 2 class2 and Week 3
Validity and invalidity limiting causes
Validity: an argument is valid if and only if t is impossible for the premises to be true
and the conclusion to be false
Limiting Cases
1. necessarily true conclusions
2. necessarily false conclusions
3. necessarily false premises
4. necessarily true premises
Philosophy of Religion
Aquinas believes god to be true
God is:
Personal
Omnipotent (All powerful)
Omniscient (knows everything)
Omni benevolent (all good)
-A logical problem which questions the existence of god:
Can god make a stone so heavy that he cant lift it???
If so then his power is limited
If not then is power is limited
5 Ways of Aquinas
WAY 1: Motion
1. In the natural world some objects move
2. in the natural world any movement requires a cause
3. in the natural world causes must come before its effects
4. in the natural world an infinite chain of causes is impossible
5. therefore, there is a first cause of motion
www.notesolution.com
6. this first cause cannot be another moving body so it is something outside the
natural world
WAY 2: General Causation
1. in the natural world some events occur
2. in the natural world no event occurs before it has a cause
3. in the natural world causes must occur before their effects
4. in the natural world a infinite chain of causes is impossible
5. therefore, there is a 1st event A*
6. A*, must have a cause, but cannot be another event in the world
7. therefore there must be something outside the world that causes the event to occur
Problems with the 1 st
two ways
some premises are questionable
consider any event requires a cause
Aristotelian and vs. Newtonian physics
Aristotle believed premises
Not until Newton/Galileo it became false
Newtons 1st law:
A body at rest remains at rest and a body in motion continue to move in a straight line
with a constant speed unless and until an external unbalanced force acts on it
**there must be a first entity to start the chain of effects
-replace motion with acceleration
Every change in motion of a body requires a cause
BUT then what about: causes must come before their effects
Is “backwards causation” impossible???
Aquinas’s inference about howthere is a cause outside nature being that, that cause is
God and not some other external force
The Birthday Fallacy
Aquinas assumes that this argument is valid
-every event has a cause
-therefore, there is a cause of every event
Many counterexamples:
www.notesolution.com
There are so many different birthdays
Why isn’t there just one day for them all?
Contingent and Necessary Beings
the contingent is what might not have existed
the necessary is what MUST exist
Possible Worlds: possible worlds are the different ways things could have been
E.g. There is a possible world where Germany won the 2nd world war
You can think of possible worlds as corresponding to long lists of sentences the sentences
that are true in this possible world
-another objection to Aquinas’s first two arguments is his claim that
cause/effect chains cannot extend infinitely far into the past. If the natural
would were infinitely old, each event could be caused by an earlier event.
Every event that occurs in nature could have cause that also existed in
nature, so there would be no reason to infer that something outside of
nature must exist as the cause of what occurs inside.
Why must every event that occurs in nature have cause?
WAY 3:
1. contingent things exist
2. each contingent thing has a time at which it fails to exist
3. so, if everything were contingent, there would be a time at which nothing exists
(call this empty time)
4. that empty time would have been in the past
5. if the world were empty at one time, it would be empty forever after (a
conservation principle)
6. so, if everything were contingent, nothing would exist now.
7. but clearly, the world is not empty
8. so there exists a being who is not contingent
contingent things exist
contingent things depend for there existence on other happenings
www.notesolution.com