Summa Theologica and The Five Ways: Proofs for the Existence of God, The Cosmological Argument

Introduction and Context:
Up until Aquinas in the 13th Century, the church's (where academia existed) doctrine was neo-Platonic.  That is, it followed the philosophy of Plato.  Why does this matter?  Recall that beginning with Plato and Aristotle, a major debate can be traced through the history of philosophy:  Is knowledge accessed internally through a priori introspection or is knowledge arrived at through empirical investigation of the world?

Aquinas is important because he revived the aristotelian tradition.  Prior to Aquinas, the most important Western proofs for God were a priori.  It was thought that to prove the existence of God, all one had to do was to rationally reflect on the concept, and through rational deduction you will arrive at a proof. Aquinas, although not an opponent of these proofs, thought you could also turn to the external world for a proof.

It should be noted that many of these proofs existed in various forms prior to Aquinas and can be found in early Islamic philosophy as well as in the writings of Plato and Aristotle.

The First Three of The Five Ways
The first 3 ways are all versions of what's known as the cosmological argument which I will focus on here:  The cosmological argument is an argument form that moves from empirical facts about the universe to the conclusion that a god/gods exist.  What sets cosmological arguments apart from many other arguments for the existence of a god/gods is that it attempts to draw on empirical evidence: this is in contrast to other argument types that are either a priori proofs (non-empirical) or proofs that rely on appeals to faith.  In the next post, I will discuss the fifth way which is known as the argument from design--but as presented by Paley.  Since the fourth way is generally not considered very important philosophically, we will overlook it.

The strength of the cosmological argument is still discussed in contemporary philosophy religion.  In this post, I will outline the specific argument made in each of the three ways, suggest some objections that are particular to each, then, by looking at Hume and others, I will discuss some objections that apply to all three versions.

The First Way:  The First Mover
This argument is essentially that, since things cannot move themselves, there must be a prime mover.   This argument is interpreted two ways.

Lay Interpretation
Imagine a long line of dominos.  The line cannot go back infinitely.  There has to be a first domino that initiates the first movement that causes the cascade of movement.

Formalized, the lay interpretation goes something like this:
(P1)  Nothing can move itself.
(P2)  Whatever is in motion, must have been put into motion by something else.
(P3)  The chain of causation implied in (P1) cannot go on for infinity.
(C1)  Therefore, there must be a prime mover that starts the initial cascade of events; we call the prime mover "God".

A problem (from a historical point of view) with the lay interpretation is that it ignores the technical meanings of the concept of motion that Aquinas employed.  When we impose our modern everyday use of "motion" onto Aquinas' argument, the argument is very easily defeated.  (P1) and (P2) are false. Animals and humans can put themselves into motion.  (P2) only works for inanimate objects--and even then, given modern theories of fundamental physics--it is dubious.

Also, on this interpretation of movement (as physical movement), there is a further reason that (P1) (and by inference (P2)) is false.  Aquinas was operating within the framework of a pre-Einsteinian model of physics in which movement is a property of objects.  But according to general relativity, movement is not a property of a thing but a relation between an object and an observer.  One of the key insights of Einsteinian physics--contra pre-Einsteinian physics--is that there is no "fixed point" in space in respect to which an object moves.  Since the argument relies on a theoretical notion of movement that is false, the whole argument fails (in this form).

The Historical/Philosophical interpretation
The stronger interpretation of the prime mover argument interprets it using the technical meaning of 'movement' that Aquinas intended.  To understand what this is, we need to make a quick detour into Aristotelian physics and metaphysics.

Detour
By motion Aristotle was referring to changes from a state of potentiality to a state of actuality.  This type of motion applies to animate and inanimate objects alike.  Consider that a lump of clay has the potential to become a clay pot (and a lot of other clay things).  In order for this potential to become actual, something (in this case, a potter) has to act on the lump of clay.  Similarly, for the universe to have moved from a state of high potential energy (pre-big bang) to one of actuality (being the universe we know of), the stuff that was the potential universe had to be acted on in order to become actual.

Another example is that someone can have the potential to be a great musician but things have to happen for that potentiality to be actualized.  And finally, in the case of human beings, the embryo is a potential human being and moves to the actualized state when it becomes a full human.

In sum, the idea of motion that Aquinas is referring to is one of movement from a potential state to an actual state--and not necessarily one of physical movement.  Also, in the argument, actualization is referring specifically to existance; that is, nothing that could potentially exist can come into actual existence without some other thing acting on that thing (in its potential state).  The key idea here is that things do not contain in themselves the power to move from potential existence to actual existence. 

Back to the 1st Way
Ok, so how does this other interpretation change things?  Well, now the argument will now go something like this:

(P1)  Nothing that potentially exists can actualize itself (i.e., move itself from a state of potentiality to actuality).
(P2)  Given (P1), it follows that whatever is actualized must have been actualized by something else.
(P3)  The regressive causal chain of actualization can't go back infinitely.
(C)   Therefore, there must be some thing that was the original actualizer; we know this thing as God.

(Request: can someone make me a T-shirt that says "original actualizer" on it?)

I'll talk about the objections after going through the other 2 ways since most of the same objections apply.

The Second Way:  The First Cause 
Ok, again, to really get a grasp on Aquinas' argument we need to go back to Aristotle.  Central to the second way is the notion of efficient cause.  Efficient cause refers to an external force whose effect is to bring something new into existence or to cause something to change into a new thing.

To make sense of this, lets consider some examples:  the efficient cause of a table is a carpenter, the efficient cause(s) of my house is all the trades people who designed and built it, the efficient cause of you is your parents, the efficient cause of the internet is Al Gore, and the efficient cause of christmas gifts is a pack of elves in the north pole...Ok, maybe some of those aren't the best examples, but you get the point.

Formalized, this argument proceeds in a similar way to the first:
(P1)  Everything has an efficient cause.
(P2)  There does not exist any thing that is its own efficient cause.  This would be impossible because in order to bring itself into existence, it would have to exist before it existed.
(P3)  The chain of efficient causes cannot be infinite going back in time.
(C)  In order for there to be a chain of efficient causes and effects, there must have been a first efficient cause.  We call this cause God.

The Third Way:  Possibility and Necessity; Aka The Way of Contingency
To understand this argument we need to familiarize ourselves with the concept of contingency.  In the context of the third way, contingency means that for something that currently exists it's also possible that it might never have existed or that it may cease to exist.  In other words, the thing's existence isn't necessary but contingent.

We can sort of simply the argument like this:  Everything in the universe that exists at some point didn't exist, might not have existed, and could cease to exist.  So, for everything in the universe, their existence isn't necessary...But things do exist! Something had to create those things.  Therefore, in order for those things to exist something whose existence is necessary has to exist.  In short, something had to start the ball rolling...and that thing's existence is necessary.  We call it God.

With this in mind, we can formalize the contingency argument like this (from SEP):

(P1)  A contingent being exists (he's talking about YOU!).
(P2)*  There there must be a cause or explanation for the contingent being's existence. (Aka, the principle of sufficient reason)
(P3)  The cause of or explanation for the contingent being's existence cannot be itself.
(P4)  The cause of or explanation for the contingent being's existence must be either other contingent beings (he's talking about your momma and papa!) or a non-contingent (i.e., necessary) being.
(P5)  Other contingent beings are not a sufficient cause or explanation of another contingent being's existence.
(C1)  Therefore, whatever explains the existence of a contingent being must also include a necessary being (i.e., non-contingent).
(MC)  Therefore, a necessary being exists (such that it cannot not exist).  This is God.

*Quick note on the principle of sufficient reason (PSR).  This is a generally (but non unanimously) agreed upon philosophical principle that for every fact (in this case, "x exists") there must be an intelligible cause or explanation.

Analysis
(P1) is fairly uncontroversial but it's not clear that its truth gets us all the way to the conclusion because just because some things are contingent doesn't mean that everything, including the universe, is.  What some contemporary advocates of this argument suggest instead is that (P1) should refer to the universe; that is, it should say that the existence of the universe is contingent.

This sounds pretty good from the point of view of the contingency argument.  We can ask, why is there a universe rather than no universe?  That we can ask this question seems to support the idea that the universe is contingent (since it's possible that it might not have existed).  But making this premise acceptable is going to require further argument--a simple assertion is not enough.  In reply, someone can simply assert the contrary: that the universe is not contingent.  Since both positions can be seen as arguing from a positions of ignorance, there doesn't seem to be any good reason for which we should accept one position over the other.

There is another problem that arises if we use the universe as the contingent being in (P1).  Recall that the cosmological argument is supposed to be a naturalistic argument; that is, it appeals to the known laws of nature to argue for the existence of God.  But it doesn't seem like there are any natural laws that we could appeal to in order to explain how God created a universe out of nothing.

As far as science is concerned, there are scientific theories that explain what the universe was like about a second before the big bang, but not prior to that.  Any account of what happened before that is going to have to appeal to non-natural (i.e., probably supernatural) explanations.  The problem here is that this defeats the whole purpose of the cosmological argument.

General Objections To All 3 Ways
The main problems are (a) supposing we accept the sub-conclusions (that there must be a first mover/cause/necessary being) it doesn't seem to follow (without further argument) that this thing is a divine entity with divine properties.  Another problem is that (b) it's possible to reject the premise that there can be no infinite regress.  The third problem is that (c) these arguments all seem to be cases of special pleading.  If everything requires a prior cause, why doesn't God need one?  That the "buck" stops at God seems totally arbitrary.  A fourth problem, related to the third, is that (d) instead of saying God is the end of the causal chain, why not just say it's the universe?  Saying that the universe has always existed, in one form or another, seems to many to be just as plausible as saying God always existed then created the universe out of nothing.

Further Objections:
Sample Size of One
This objection is a further elaboration of (d).  If we apply the cosmological argument to the universe, rather than to individuals, several problems arise, in addition to those mentioned in the section on the third way.  Russell and Hume argue that our notion of causation comes from our experience with particular classes of things.  However, there is only one universe, so we cannot apply our notions of causation to things that are a set unto themselves:  we have no prior experiences from which to infer causal laws about universes, only about things in universes.  Because we are in a position of ignorance in terms of whether universes require a cause,  Russell's position is to simply say "the universe is 'just there', and that's all."

A possible reply is that just because we haven't experienced other universes doesn't mean we can't make the inferences that it needs a cause.  The universe is contingent and therefore requires an explanation for its existence or a cause for its existence.

However, the problem here is that the reply only works if we assume the universe is contingent.  There doesn't seem to be any good reason for this supposition.  Also, typically defenders of the "the universe is contingent camp" make this inference from the fact that objects in the universe are contingent.   But this is the fallacy of composition.  Just because the things that make up a whole have a particular property doesn't mean the "whole" has that property.

An example of the fallacy of composition would be: atoms are colorless, cats are made of atoms, therefore, cats are colorless.  So, just because things in the universe are contingent and necessarily caused, it doesn't follow that the universe itself is contingent and necessarily caused.

Necessity and Contingency:  It All Depends on your Point of View
Back in (P2) of the argument from necessity and contingency (the third way), we invoked the principle of sufficient reason to show why there had to be some necessary cause for things with contingent existence. The principle of sufficient reason is that if something is contingent then there must be an explanation of or cause of its existence.  Hume argues that the contingent things are sufficiently explained when we appeal to the fundamental parts that make them up.

Hume's argument is best understood through example.  Consider a table.  The table is made up of atoms.  The fact that we call that collection of atoms "table" is simply a psychological fact about how our mind works.  There's no real thing called "tables",  there are only different configurations of elementary particles, and our minds apply names to certain similar structures.   So, at its base, reality is just collections of fundamental particles.  We don't need to provide causal explanations for each fundamental particle.  They just exist.  So, the table exists because it's made of fundamental particles in a particular arrangement.

Notice how this is kind of like Russell's position except from the opposite point of view.  Russell said the universe just is a brute fact, not contingent, and doesn't require a causal explanation.  Hume's saying that contrary to the "contingent things" version of (P1), the parts of the universe are not contingent.  People are mistaken about what the parts are.  The parts of the universe are not people, tables, and chairs.  The parts of the universe are just fundamental particles and they don't require a causal explanation for their existence.  They just are!

The reply to this is that the principle of sufficient reason still requires an explanation for why the particles are arranged as they are and why they exist rather than don't exist.

A possible counter reply is that energy and the fundamental particles of matter don't require a causal explanation for their existence.  Sure, they change form from one to the other but the total combined amount of each never deviates from the laws of conservation of matter and energy.  Energy and matter transmutate but are never lost or destroyed.  Therefore, matter is contingent in regards to its form but necessary in regards to its existence.  And the contingent argument is all about existence, not about form, so the fact that there is no explanation for the form doesn't matter.