God Is: An Introduction to the Evidence for God, Part 3

St. Thomas Aquinas, The First Way: The Argument from Motion

  1. We see that some things are in motion.
  2. Whatever’s in motion is put in motion by something other than itself.
  3. If what put it into motion was also put into motion, then it was also put into motion by something other than itself, and that by yet another, and so on.
  4. But this can’t go on forever, since then there would be no first mover to move the others, and so there would be no motion at all.
  5. It’s necessary, then, to arrive at a first mover that’s not put into motion by another, and everyone understands this to be God.

I’ll spend more time with the First Way, the Argument from Motion, because it sets the stage for the Second and Third Ways. Thomas regarded the First Way as the most obvious of the ways that demonstrate the existence of God, and included it in several of his writings.

Let’s look at the claim made by each premise to see if we can have confidence in the conclusion. First, we do see that some things are in motion. No one would dispute this, except maybe those who think all reality is an illusion. In that case, nothing’s real. Barring that extreme claim, I think we can call the first premise a given.

The second premise claims that whatever’s in motion is put in motion by something other than itself. This isn’t quite so obvious. What’s Thomas’ thinking here? This argument is sometimes called “The Argument from Change,” because what Thomas means by “motion” is change from potentiality to actuality. That might seem like fancy philosophy talk, but let’s try to break it down. Thomas uses the example of fire and wood. Fire is actually hot, while wood is potentially hot. The wood can’t make itself hot, because the wood doesn’t possess heat, and nothing can give itself what it doesn’t have. If that were so, then it would be possible for the wood to be potentially hot and actually hot at the same time, a clear contradiction. But, the wood does have the potential to be hot. How can the wood “move” from being potentially hot to actually hot? By being “moved” by the fire. The fire, being hot by nature – that is, if it isn’t hot, it isn’t fire – can transfer it’s heat to the wood, thereby “moving” the wood from potentially hot to actually hot.

But, why can’t we just stop at the fire and say the fire was the beginning of the series of motion? This speaks to the third premise, which claims that if something that puts another thing into motion was itself put into motion, then it was also put into motion by something other than itself, and that by yet another, and so on. So, we have to ask: From where did the fire come? There are three things fire needs to exist: heat, oxygen and something to burn. So, the fire must have been transferred from something that possessed those actualities, which then moved to the potentiality of taking fire, in order for the fire to then be transferred to the wood, and so on. Perhaps two pieces of wood were rubbed together (heat from the friction, oxygen from the environment and the wood itself is something to burn), or perhaps a match was struck against a flint, giving flame to the match. The match was then set to the wood. But, from where did the match and flint come? And so on, … . Nothing can cause itself to move from potentiality to actuality.

But what about humans and animals? They move themselves. Strictly speaking, when a cat’s tail moves, it’s the muscles, tendons and bones that are moving, which are moved in response to the motor neurons which are inspired to move by the cat’s will or instinct, which matured with the development of the cats neurological system, and so on. So, this is consistent with Thomas’ claim that whatever’s in motion is put in motion by something other than itself, if we break the movement of humans and animals down to the movement of the individual parts, and then the development of those individual parts, and then the conception of the person or animal from ovum and sperm, and so on. So, it seems that the second and third premises also stand.

The fourth premise is a still bigger claim. Thomas says that the series of movers can’t go back forever, infinitely, since then there would be no first mover to move the other movers, and there would be no movement at all. We tend to think of causes and effects happening one after another. First comes the cause, then the effect. But, consider the example Thomas offers of a hand moving a staff. The hand doesn’t move prior to the staff. Rather, the staff moves with the hand. Perhaps the staff is being used to stir a pot of stew (well, alright, we’ll put down the staff and use a spoon). Then the hand, the spoon, and the broth, along with all the ingredients, are moving at the same time. It’s in this sense that an infinite regression of causes is impossible, for if there were no first mover, then there would be no movement at all, because none of the members of this series of movers have the ability to move independent of the first mover. They’re all moving, and only moving, because of the action of and their relationship to the first mover. The spoon, broth and ingredients have no power to cause themselves or anything else to move of themselves. They all move only because the hand moves. If the hand never moved the spoon in the first place, then the spoon would never have moved, and neither would the stew.   Also, If the hand should stop moving, so would the spoon, so would the broth, and so would the beef cubes, potatoes, carrots, etc, … . Thomas isn’t arguing that the first mover initiated movement at some particular moment in the distant past, but that the first mover is the cause of movement now, or at any moment, for that series of movers. A series of movers ordered this way must have a first mover, or the other movers wouldn’t move at all, for the only reason they move is because of the action of and their relationship to the first mover. The fourth premise stands.

There must then be a first mover, ultimately responsible for all movement from potentiality to actuality, a mover who isn’t moved from potentiality to actuality by another, but that has the power to move others from potentiality to actuality: an unmoved mover (“unmoved” not in the sense of “inactive,” but in the sense of not needing to be moved by another in order to move). Such an unmoved mover would possess no potentiality, but only actuality; in other words, a being that is pure Act. This is God. God doesn’t have potential. God already actualizes every perfection. God is pure Act, the first mover.

Next Wednesday, I’ll address objections to the Argument from Motion.

Be Christ for all. Bring Christ to all. See Christ in all.

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