Aquinas’s First Way – highlights

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# Aquinas’s First Way – highlights - PowerPoint PPT Presentation

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.

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Presentation Transcript
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.
• 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