In Defense of The Third Premise

This is in response to a friend’s critique of my argument for the existence of God

Whatever is changeable is changed in the act of changing another

By this premise, in order to change something, one must change himself. This means the unchanged changer is either (A) an exception to the rule, whatever is changed must be changed by another, or (B) both the changer and not the changer at the same time.

If we are going to say a contradiction exists, or an exception to a rule exists, why this exception and not another? Or, why not admit to the many other contradictions we could imagine as solutions? We could assume that there is an entity that has both potentiality and actuality which caused everything. It would be an exception to the rule, but so is the proposed solution.

By the way, If I use the word ‘move’, it will be in the classical sense. I mean something more than locomotion. I mean change in general.

  1. Are you denying the third premise?
  2. In that case, here’s support: motion is a principle of bodies.
  3. Even if we don’t know the Unmoved Mover is pure act, it’s still divine, and we’ve reached a sort of weak Theism.
  4. But even in this case, here’s an argument for a being of Pure Act.
  5. Alternatively, there is always Feser’s approach.

Are you denying the third premise?

I’m not sure what you’re getting at here. The premise was, whatever contains potency in its being, if it causes something to change, it must change in order to do so. (When a stick moves a stone, the stick is moved in order to do so.) So you’re saying that the unchanged changer is an exception to this? Not really, it’s not in the same category, since it’s not capable of change. Now, it is an exception in the sense that, what we see -nature- is given to motion. The whole point of the argument is that there is a cause of the natural.

It’s like an email that is forwarded and forwarded and forwarded: an argument concludes that there must be an exception to the apparent rule: “emails are forwarded by another.” However, all forwarded emails are forwarded from another email. Clearly there is an email that was sent without being forwarded.

“We could assume that there is an entity that has both potentiality and actuality which caused everything. It would be an exception to the rule, but so is the proposed solution.”

But think about what this means: an entity that is changed in some way, which causes all change. So then it changes itself? But here, we’re not just finding an exception to “changers are themselves changed,” it’s also an exception to “whatever changes is changed by another.” But as we saw, this is by the very nature of act and potency, and the most basic rule of causality: out of nothing, nothing comes; and potency does not raise itself to act, because it is not actual.

I think what you’re trying to articulate is just a denial of the third premise.

In that case, here’s support: motion is a principle of bodies.

The following is an argument for the third premise. Locomotion is the foundation for other motions or change. We can see this in something like radiation – the candle cannot heat my hand unless it is brought near to my hand. Even gravity fields are proportional to proximity. Since, locomotion is a principle of bodies, and bodies are by nature 1) extended, 2) divisible and 3) cause locomotion and change by changing (size, location, orientation, etc). Even in the case of fields and waves, such things are both changing in order to change, and are features of and operate on bodies.

If this is true, we have support for premise three, and the conclusion follows: The First Mover is devoid of potency.

But perhaps the objection is trying to say, “maybe the Unmoved Mover is an exception because even though it can be moved, it moves others without being moved, itself.”

Even if we don’t know the Unmoved Mover is Pure Act, it’s still divine, and we’ve reached a sort of weak Theism.

It’s clear that for something to cause change without in anyway changing is not natural. We can think of it in physical terms: if energy is a currency of change, this is an entity that causes change without exchanging energy. It causes a series of exchanges of energy without ever gaining or losing energy. It’s an entity outside the realm of the first law of thermodynamics (how’s that for a demarcation of natural/supernatural?). It’s something that causes locomotion without being in motion, heats without having heat, teaches without being taught… and does all without changing in some other way.

Even in this case, here’s an argument for a being of Pure Act.

After considering change, act and potency, we start with certain logical possibilities: changers, things that change, things that do not change; act by itself, act and potency, and potency by itself. Act by itself is God, act and potency together is the category in which we find the natural, and potency by itself is non-existent.

The claim in the third premise is, everything seems to move when moving something else. The one exception to this would be things that are unmovable that can move others.

But suppose we ask, can things that are moveable sometimes move others things without being moved? Can there be unmoved movers with respect to one motion, but moved at other times? Or with respect to another motion?

Remember, from this point we’re squarely in the realm of the supernatural. And we’re hypothetically positing a type of change or motion that is beyond locomotion, and does not require proximity in any way.

Every possible motion needs to be traced back to a first mover: something that is the cause of that motion. But if that thing is moved, we haven’t yet found the cause of all motion, because we haven’t found the cause of that motion.

Can there be a potency that just so happens to exist without an act to actualize it?

  • A potency is a potency for some act. The potential to be changed to a certain state, presupposes the actual state. My hand does not have the potential to be hot, if there is nothing to actualize the heat. The train to Vancouver is not the train to Vancouver if there is no Vancouver. The conductor, the engine, and the paying passengers all cause the train to actually reach Vancouver.
  • Now the end state of a potential, the act of the potency as act, exists in the total cause in some way. Vancouver is in the mind of the conductor, and the power to cover the distance in the fuel in the engine, and the payment of the passengers, otherwise, it just isn’t the train to Vancouver.
  • So if a potency is for some act, and that act must be in some way be contained in any cause that is able to actualize this potency, to say there is a potency, is to say there is some act outside of this potency.

But then suppose there were two mutually moving entities. (Our even a googol of such entities.) Taken as a whole, they would be the principle cause of all motion. But then taken as a whole, they would contain all act, as act, and not simply in potency. What one part had in potency, the other part would have in act.

  • But what is composed of parts, is in potency to those parts, which presupposes the act capable of composing those parts, and thus something outside it.
  • Since potency is that which differentiates, the two entities would be different only in what they have in potential. But if they mutually actualize their potencies (and they do so in an unmoved way, since otherwise, they’d be natural objects), they would then be purely actual.
  • But now they are no longer two entities but one, purely actual entity, since potency is the only thing which differentiates.

Therefore, no matter what we arrive at a purely actual entity. But again, we’re squarely outside of the natural.

Alternatively, there is Feser’s approach.

Edward Feser’s version of the first way bypasses this objection by considering a thing’s potential for existing differently, and says that that thing’s potential for existing the way that it does (in order to support the series of motions it does), needs to be actualized by something outside itself. And in this way the series continues until we reach an unmovable unmoved mover: something utterly devoid of potency. See footnote 6 on the first article. Or this lecture.


The third premise of my version of the First Way either stands, or just isn’t required to arrive at a basic sort of Theism. If we have indeed concluded to a cause of all natural motion that isn’t in motion itself, we’ve left naturalism and atheism behind. Any further discussion is Theology.

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