Aquinas’s First Way – highlights

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.

Aquinas’s First Way – highlights