Cosmological Arguments

Cosmology: u  Study of the origins of the

Universe u  Why is there something rather than

nothing? u  Where did everything come from?

u  Where did the stars come from?

u  Aquinas: u  If the things we see were caused

to exist by things that existed previously;

u  And those things were caused to exist by things that existed previously;

u  Etc., etc., u  Doesn’t that mean there must

have been a “first cause?” u  An uncaused causer?

u  Or could the series of “prior causes” go on to infinity?

Arguments that God exists: Review

•  Ontological: the existence of God follows from the very concept of God. –  exp: Anselm’s Ontological Argument

•  This is the only a priori argument for the existence of God.

•  Cosmological: The existence of God is posited to explain the existence of things in the world. –  exp: Aquinas –  This is an a posteriori argument, in that it relies on

something we know only from sense experience—namely, that there is change in the world.

The Cosmological Argument:

•  An a posteriori argument because it begins with a premise, based on observation, that the universe exists, and is subject to change.

•  It tries to show that for this to be so there must exist something outside the universe which can cause or explain its existence.

Aquinas’ Second Way: Summa Theologica: c. 1270

•  1. Some things are caused to exist by things that already exist.

•  2. Nothing can cause itself to exist. (If so, it would have to “precede itself.”)

•  3. This series of prior causes cannot go on to infinity. –  (His argument for this is on the next slide.)

•  4. So, there must be a first cause—an uncaused causer.

Aquinas’ Reasoning •  We see that at least some things are caused to exist by

things that already existed. •  But nothing can cause itself to exist.

–  To cause itself to exist, a thing would have to exist before it existed, which is absurd.

•  So everything there is has been caused to exist by something that already existed.

•  This series of “prior causes” cannot go on “to infinity.” •  So there must be a “first cause,” i.e., something that causes

other things to exist, but was not itself caused by anything prior to it.

•  And this is (part of) what we mean by “God.”

This cannot go on to infinity. “Such a series of causes must however stop somewhere…. Now if you eliminate a cause, you also eliminate its effects, so that you cannot have a last cause [or “last effect”] … unless you have a first. Given therefore … no first cause, there would be no intermediate causes either, and no last effect.”

–  i.e, without a first cause, nothing else would have happened, and so nothing would be happening now.

–  But things are happening now. –  So, the series cannot go on to infinity.

Why must the series “stop somewhere?”

•  Aquinas’ Answer: –  Because without a first cause, nothing else would ever have

happened, and so nothing would be happening now. •  (But, as we know by experience, things are happening now.)

•  So, if things are happening now (and they are), then

there must have been a first cause.

•  Hmmm…. What is going on here?

Loop-d-Loop!

•  Since nothing can cause itself, all existing things were caused by prior existing things.

•  Either this series of prior existing things goes on forever backwards in time, or there was a first cause. –  If the series went on forever, everything would be caused

by something other than itself, without a beginning.

•  Aquinas says it couldn’t have gone on forever, because then there wouldn’t have been a beginning.

•  So, there must have been a first cause.

But …

•  Why would nothing be happening now if there wasn’t a beginning? –  To say there wasn’t a beginning is simply to say that things

are happening now because everything was caused by a prior thing, which was caused by a prior thing, and so on forever, without any beginning.

–  So, Aquinas’ only reason for rejecting an infinite series of prior causes is his belief that there must be a first cause.

–  But this is the very point he is trying to prove!

“Circular” Reasoning

•  Aquinas is reasoning “in a circle” by pre-supposing the very point he is trying to “prove.” – There must be a first cause, because the series of

prior causes can’t go on forever. – The series of prior causes can’t go on forever

because there must be a first cause. – This amounts to: there must be a first cause

because there must be a first cause!

“Begging the Question”

•  An argument “begs the question” when it simply “assumes” (or “begs”) the question or point that is being argued about. –  The purpose of an argument is to convince you of

something you didn’t already believe. –  An argument “begs the question” when is pre-supposes the

very point it is trying to convince to believe. –  These arguments don’t don’t give any (new) reason to

believe something you didn’t already believe.

Aquinas Begs the Question

•  Aquinas is trying to prove that there must be a “first cause.” –  He argues there must be a first cause because otherwise the

series of causes would to on to infinity. –  He argues the series of causes cannot go on to infinity

because then there would be no first cause. •  This amounts to arguing that there must be a first

cause because otherwise there wouldn’t be first cause.

Why did Aquinas Beg The Question?

•  This is a good question! –  Can we really understand what it would mean for “the

series to go to infinity?” –  Can we really understand what it would mean to say that an

infinite amount of time already taken place? –  Aquinas seems unable to even see this as a possibility. –  But since Aquinas’ time, other have at least seen this as a

possibility. •  There is nothing mathematically impossible about this idea.

–  So, we can’t dismiss this option without argument.

Infinite Past?

•  Aquinas thinks that everything must have a cause or explanation.

•  But he seems unable to even conceive that the universe might have an infinite past.

•  And so he reasons there must be “first cause,” because 1)everything must have a cause, and 2) the series or prior causes cant go on forever.

An Infinity of Explanations?

•  But, if the universe did have an infinite past, then wouldn’t everything have a cause, even without any “first cause?” –  Yes! Everything, that is, except the infinite series of

past causes itself. It would not have a cause.

–  Must it also have a cause or explanation? Suppose it does. Call that cause “G.” Doesn’t “G” need an explanation? If we need an explanation for the infinite past history of the world, then won’t the series of explanations need to go on forever?

Causes and Explanations

•  We want to explain things. •  The Cosmological Argument

“posits” (hypothesizes) the existence of God to explain where the universe (the “cosmos”) came from.

•  But how much can we explain?

How much can we explain?

•  If every fact must have an explanation, where can we stop? –  If we need God as an explanation of the infinite series,

don’t we need an explanation of God? –  If some things (like God) don’t need an explanation,

why does the infinite series need an explanation? •  Which is harder to accept?

–  That some facts cannot, even in principle, ever be explained; or

–  That there must be some single being that explains everything, including itself?

Summary:

•  In discussions of the “cosmological argument,” we see that questions about the existence of God seem directly connected with our need to find reasons or explanations for everything.

•  Philosophers seek answers to questions that can’t be answered solely by an appeal to sense experience.

•  So, it seems that ideas about the existence of God stem from the very parts of us that urge us to seek answers to philosophical questions.