Aquinas’s First Way – highlights

• It’s impossible for something to put itself into motion.

• Therefore, anything in motion is put into motion by something else.

• There isn’t an infinite regress of movers in motion.

• Therefore, there is a prime mover, something that moves without itself being in motion, God.

Aquinas’s First Way

• No self-movers:– If x puts y into motion, then there’s

some respect in which x is in actuality and y is in potentiality.

– It’s impossible for something to be in actuality and in potentiality in the same respect.

– Therefore, it’s impossible for something to put itself into motion.

Aquinas’s First Way

• No infinite regress– If there were an infinite regress of

movers, there’d be no first mover.– But if there were no first mover,

there’d be no subsequent movers.– And there clearly are movers.– Therefore, there isn’t an infinite

regress of movers.

Aquinas’s First Way –full-dress version

• [Anything in motion is put into motion by something.]• It’s impossible for something to put itself into motion.

• If x puts y into motion, then there’s some respect in which x is in actuality and y is in potentiality.

• It’s impossible for something to be in actuality and in potentiality in the same respect.

• Therefore, anything in motion is put into motion by something else.

• [If everything in motion were put into motion by something else itself in motion, there’d be an infinite regress (or a loop?)]

• There isn’t an infinite regress of movers in motion.• If there were an infinite regress of movers, there’d be no first mover.• But if there were no first mover, there’d be no subsequent movers.• And there clearly are movers.

• Therefore, there is a prime mover, something that moves without itself being in motion, God.

• [I suspect Aquinas needs further argument to show that there is only one prime mover]

Craig’skalam cosmological argument

• Whatever begins to exist has a cause.• The universe began to exist.• Therefore, the universe has a cause.• If the universe has a cause, it must be

– immaterial, timeless, and changeless– uncaused– personal

• Therefore, the universe has an uncaused, immaterial, timeless, changeless, and personal cause.

The universe began to exist

• Mathematical-philosophical:– Actual infinites avoid contradiction in the

mathematical realm only due to certain restrictions.

– But such restrictions have no place in the real world.

– Therefore, actual infinites could not avoid contradiction in the real world.

– If the universe didn’t begin to exist, then there would be an actually infinite number of past events.

– Therefore, the universe began to exist.• Scientific:

– According to standard Big Bang cosmology, the universe began to exist.

Whatever beginsto exist has a cause

• Obviously true– Something cannot come from nothing.– “[T]hings cannot just pop into being out of

nothing.”• Quantum mechanics?

– Only certain interpretations of quantum mechanics involve indeterminism, and even those do not involve anything coming into being from nothing.

• What about God?– God doesn’t begin to exist, so the principle

doesn’t apply to God.– The universe, on the other hand, did begin to

exist, so it must have a cause.

Getting to God• Immaterial, timeless, and changeless

– The cause of the universe is not located within space or time.

• Uncaused– The cause of the universe cannot have a cause,

because “we’ve seen that there cannot be an infinite regress of causes”

• Personal– The cause must somehow be timeless and yet

have a effect in time.– But if the timeless cause were impersonal and

“mechanical”, then it would have a timeless effect—i.e., then the universe would be eternal.

– So the timeless cause must be a person who freely chooses to bring about a effect in time.

Infinity• Can actual infinites exist in the real world?

– If numbers are real, then, since there are infinitely many numbers, it follows that actual infinities do exist in the real world (hence Craig rejects Platonist realism about numbers).

– If space consists of infinitely many segments, then actual infinities do exist in the real world.

– N.B.: It’s not enough for space to be infinitely divisible. Craig will say that this is a merely potential infinite, not an actual infinite.

• Isn’t God infinite?– Craig’s arguments are against the real existence of

an actually infinite number of things.– Presumably God is infinite in some other sense of

the term.

Causation

• ‘Begins to exist’– x exists at some time, and there is some time

immediately beforehand where x doesn’t exist• This doesn’t apply to the universe• Can something begin to exist without a cause in

this sense?– x exists at some time, and there is no time

beforehand• This does apply to the universe• Can something begin to exist without a cause in

this sense?– Perhaps the premise ‘whatever begins to exist

has a cause’ is less plausible in the second sense (the one that applies to the universe).

Causation

• Simultaneous causation– On standard Big Bang cosmology, let’s suppose,

there is no time before the universe.– But if a cause must precede its effect in time,

then the universe has no cause.– So Craig rejects the claim that a cause must

precede its effect: he allows for simultaneous causation (ball-cushion example).

• Creation ex nihilo– Craig holds that God created the universe ex

nihilo—out of nothing.– But if it seems obviously true that nothing can

begin to exist without a cause, doesn’t it also seem obviously true that nothing can be created ex nihilo?

Part IX

• Demea’s argument– It’s a cosmological argument– He calls it “the argument a priori”– It’s supposed to get you all the way to a

theistic God: i.e., only one God, who is infinite

• A priori vs. a posteriori– The term a priori is often used to mean

‘independent of experience/observation’—math is supposed to be a priori

– And a posteriori is used to mean ‘based on experience/observation’—the natural sciences are supposed to be a posteriori

Demea’s argument• Principle of sufficient reason (PSR)

– “Whatever exists must have a cause or reason of its existence”

• Two options– Either “tracing an infinite succession, without any

ultimate cause at all” or “at last hav[ing] recourse to some ultimate cause, that is necessarily existent”

• The first option is absurd– For “the whole eternal chain or succession...

requires a cause or reason, as much as any particular object which begins to exist in time”

– “The question is still reasonable, why this particular succession of causes existed from eternity, and not any other succession, or no succession at all.”

• So we’re forced to accept the second option

Cleanthes’ objections

• No a priori proofs of existence claims– When you demonstrate something a priori,

you show why the opposite is inconceivable and contradictory.• Like in math

– But with existence claims, both sides are conceivable, neither one is contradictory.• Whatever we can conceive of as existing, we can

also conceive of as not existing

– So it’s impossible to give an a priori demon-stration of a thing’s existence.

Cleanthes’ objections

• “Necessary existence”– If something’s existence is necessary,

then its nonexistence should be inconceivable.

– But you can always at least conceive of a thing’s nonexistence.

– So there can’t be any such thing a necessarily existing being.

Cleanthes’ objections• Necessary being: God or Universe?

– Even if there is a necessarily existing being, why think it’s a theistic God? Why not just say it’s the physical universe?

– Admittedly, it’s hard to see how the physical universe could be a necessarily existing being—after all, we can always conceive of the nonexistence of any lump of matter.

– But (as just mentioned), it’s equally hard to see how God could be a necessarily existing being—after all, it’s equally true that we can always conceive of God’s nonexistence.

Cleanthes’ objections

• Causation and priority in time– If there’s an infinite chain of

contingent beings, then there isn’t any time before all the contingent beings.

– But a cause has to be before its effect.

– So there can’t be a cause of an infinite chain of contingent beings.

Cleanthes’ objections

• No need for extra explanation– If there’s an infinite chain of contingent

beings, then there’s a satisfactory explanation for each individual contingent being.

– But if each individual is explained, then the entire collection of individuals is also explained.• After all, it’s not like the collection is some

brand-new thing, over and above all the individuals.

– So there is nothing left unexplained.

Philo’s objection

• Perhaps everything’s necessary– It might well be true that everything

in the physical universe, even though it seems contingent, is actually necessary.

– If so, it would be impossible for things to be different than they are.

– And so there’d be no need to explain why things are this way instead of that way, or why there’s something instead of nothing.

Philo’s closing observation

• This argument only convinces metaphysicians– People who are into abstract

reasoning about deep topics (especially people who do mathematics) are the only ones who put any stock in such arguments.

– Everyone else can’t shake the feeling that the arguments have some problem somewhere, even if they can’t put their finger on what’s wrong with them.

Modal cosmological arguments(Review)

• The target– What’s the target? The view that says there’s nothing

but contingent beings.– The goal is to disprove this view.– If successful, it follows that there is a necessary being.

• The problem– If there’s nothing but contingent beings, then we’re

left with an unexplained fact.– There’s no explanation for why this collection of

contingent beings exists rather than some different collection or nothing at all.

– So the problem is that this view leaves us with a ‘brute fact’—an unexplained collection of contingent beings.

– [I should add that Aquinas seems to have a different problem with the ‘nothing but contingent beings’ view.]

Modal cosmological arguments(Review)

• Nothing but contingent beings– There could be nothing but a finite chain of dependence.– There could also be nothing but an infinite chain of

dependence.– There could also (perhaps!) be nothing but a loop of

dependence.

• The PSR– But on any of these options, something is left

unexplained.– In particular, on any of these options, the question “Why

does this chain/loop exist?” has no answer.– This violates the Principle of Sufficient Reason, which

says that there is an explanation (a reason/cause) for everything (everything that exists, or every positive fact, ...)

Hume’s most famous objection(Review)

• An infinite chain would satisfy the PSR– Cleanthes says that, with an infinite chain

of dependence, nothing is left unexplained.– After all, each individual is explained by

the previous individual.– And the collection of individuals isn’t

anything over and above all the individuals.

– So, since each individual is explained, then the entire collection is explained.

– So the PSR is satisfied—everything has an explanation.

Possible replies to Hume• Loop reply

– In a loop of dependence, each individual is explained by the previous individual.

– But it looks like this leaves the entire loop unexplained.– So this shows that, even if every individual in a collection is

explained, the entire collection might still be unexplained.– [Perhaps Hume can get out of this problem by insisting that

there couldn’t be a loop of dependence in the first place]• Circularity reply

– Hume says there’s an explanation for the entire collection.– But what is this explanation? What gets cited in this

explanation?– The only beings that exist are the ones in the infinite chain,

so those are the only beings that could be cited in an explanation.

– So any explanation of the entire collection would have to cite beings belonging to the collection.

– So any explanation would be circular.