Due to space constraints, we are only covering the first of the five ways in this post, but four more will allow for us to cover the whole of the Five Ways. That will be what I will be covering in the next few posts.
The Quinque Viae (Five Ways) are a series of Scholastic Arguments that form a cumulative argument for the existence of God. As a cumulative argument they are designed to stand together, like threads in a rope, rather than as individual arguments for God’s existence. Surely they can be used individually but they were not designed for this purpose.
Similarly, Thomistic philosopher Edward Feser has stated that the arguments themselves are not comprehensive, but seem rather to be a summary introduction for beginners.  This means they are not written like a full-fledged argument, which means that instead of taking the time to explain and flush out his premises, they are instead simply stated and then the conclusion follows. This can be explained in that Aquinas’ Summa Theologica, where the Quinque Viae are found, was an instructional guide for beginners who were learning in the Catholic Church. It was steeped in Aristotelian Metaphysics and Scholastic distinctions which are filled out in the full body of Aquinas’ work. Thus, a student who had questions about the Quinque, could pursue the metaphysical foundations in other works.
“Because a doctor of catholic truth ought not only to teach the proficient, but to him pertains also to instruct beginners. As the Apostle says in 1 Corinthians 3: 1–2, as to infants in Christ, I gave you milk to drink, not meat, our proposed intention in this work is to convey those things that pertain to the Christian religion, in a way that is fitting to the instruction of beginners.” 
With this context in mind, we can continue into actually looking at the Quinque, which take up a whole page and a half of the full three thousand of the Treatise(which shows just how assumed the existence of God was taken in this work of the Church.), but are nonetheless fairly powerful in their sophistication and distinction.
Via Unus: The Unmoved Mover.
“The first and more manifest way is the argument from motion. It is certain, and evident to our senses, that in the world some things are in motion. Now whatever is in motion is put in motion by another, for nothing can be in motion except it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. For motion is nothing else than the reduction of something from potentiality to actuality. But nothing can be reduced from potentiality to actuality, except by something in a state of actuality. Thus that which is actually hot, as fire, makes wood, which is potentially hot, to be actually hot, and thereby moves and changes it. Now it is not possible that the same thing should be at once in actuality and potentiality in the same respect, but only in different respects. For what is actually hot cannot simultaneously be potentially hot; but it is simultaneously potentially cold. It is therefore impossible that in the same respect and in the same way a thing should be both mover and moved, i.e. that it should move itself. Therefore, whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover; as the staff moves only because it is put in motion by the hand. Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.” 
It is easy to make the mistake (as Dawkins did) to assume that he’s speaking here of motion in the contemporary sense. It should be more broadly construed, due to the terminological use in Aristotelian physics, to mean something closer to ‘change’. Motion is linked to the change from potentiality to actuality of certain properties in a creature, but is not limited to a change in place (though certainly a change in location is part of the argument. Think of the change from potential to kinetic energy in modern physics for example.) Aquinas would have undoubtedly sent his students to Aristotle’s Physics and Metaphysics, and his own commentary on those (as well as probably Averroes’ commentaries.) for full arguments for these premises, we thus will not deal with them here.
Therefore, assuming these premises, let us examine the full scope of the argument rephrased like an argument you might find in a contemporary paper.
- Some things change from potentiality to actuality
- Potentiality cannot change itself into actuality.
- An actual infinite regress of potentiality cannot be traversed into actuality.
- There must therefore, be a source of change that is not itself potential. (Pure actuality)
- This is what we mean by God.
This argument is in my opinion, fairly sound. It does depend on some other arguments to root some of its premises, but so does any argument that isn’t self-evident. For example, for 3) we would have to depend on paradoxes of infinity and arguments from the absurdity of their existence. For example, Ghazali’s arguments against an actual infinity deal with examples of how we have to accept some unacceptable consequences in terms of physical numeration. For example, that Saturn and Jupiter, though they have a different number of rotations because they rotate at a different rate, if they had been rotating for an actual infinite amount of time, then their rotations are numerically the same. Namely: actually infinite. Further examples would include David Hilbert’s Infinite Hotel Paradox.
To better understand the idea of change let us look at a concept from modern physics: Potential and Kinetic energy.
The potential energy equation for any given object is PE=mgh. M=mass of the object, g=the force of gravity, and h=the height of the object from the ground. So if we have a 1kg object, .5 meters off the ground, then you get PE=1(-9.8)(.5)=59 J. So we have an object at rest, yet containing 49 Joules of potential energy.
The problem with potential energy is that it is just that, potential, there has to be a change to the system in order for the energy to become usable. Under no circumstance will the object change itself; the object will never give off that potential energy in kinetic energy unless an outside change occurs. The floor disappears or the book slides off the table and begins its fall. This change cannot occur from the potentiality itself, but requires an outside cause. This is one of Newton’s laws of motion. An object in motion stays in motion unless acted on by an outside force. At any point in time, any object has potential for movement in any direction, but no internal power will force it to move a different way causelessly.
And that is basically the argument. Potentials cannot convert themselves into actuality without an outside cause, and outside causes cannot extend to actual infinity because of the difficulty of an actually infinite number of things as well as the impossibility of traversing the infinite. (Think Zeno’s paradoxes).
Next time we’ll look at the second way, the argument from causation, which is similar, but different in emphasis than the first way.
 : Feser,Edward (2009). Aquinas, A Beginner’s Guide
 : ST, 1. 1
 : Prima autem et manifestior via est, quæ sumitur ex parte motus. Certum est enim, et sensu constat, aliqua moveri in hoc mundo. Omne autem quod movetur, ab alio movetur. Nihil enim movetur, nisi secundum quod est in potentia ad illud ad quod movetur, movet autem aliquid secundum quod est actu. Movere enim nihil aliud est quam educere aliquid de potentia in actum, de potentia autem non potest aliquid reduci in actum, nisi per aliquod ens in actu, sicut calidum in actu, ut ignis, facit lignum, quod est calidum in potentia, esse actu calidum, et per hoc movet et alterat ipsum. Non autem est possibile ut idem sit simul in actu et potentia secundum idem, sed solum secundum diversa, quod enim est calidum in actu, non potest simul esse calidum in potentia, sed est simul frigidum in potentia. Impossibile est ergo quod, secundum idem et eodem modo, aliquid sit movens et motum, vel quod moveat seipsum. Omne ergo quod movetur, oportet ab alio moveri. Si ergo id a quo movetur, moveatur, oportet et ipsum ab alio moveri et illud ab alio. Hic autem non est procedere in infinitum, quia sic non esset aliquod primum movens; et per consequens nec aliquod aliud movens, quia moventia secunda non movent nisi per hoc quod sunt mota a primo movente, sicut baculus non movet nisi per hoc quod est motus a manu. Ergo necesse est devenire ad aliquod primum movens, quod a nullo movetur, et hoc omnes intelligunt Deum.
 : Interestingly, potentially infinite sets cannot make themselves actually infinite by any amount of addition. They are ontologically distinct.