An Introduction to the Five Ways of St. Thomas Aquinas, Part 6

Objections to The Argument from Motion

As one might expect, philosophers both atheist and otherwise have raised objections to Thomas’ Argument from Motion for the existence of God. I discussed some objections in the article introducing Thomas’ Argument from Motion. Here, I’ll discuss some other common objections.

If nothing can move itself, how was the first mover (God) able to move?

This objection is rooted, not in a denial of the existence of a first mover, but in a misunderstanding of the nature of the first mover and in what Thomas means by motion. In order to be the first mover, the first mover by definition must be capable of moving without being moved by another, just as fire by definition must be hot or it isn’t fire, or a triangle by definition must have three sides or it isn’t a triangle. Otherwise, if the first mover were moved by another, it clearly wouldn’t be the first mover, and our search for the first mover would have to continue.

Remember that what Thomas means by “motion” isn’t merely movement in space, from one place to another, but movement from potentiality to actuality. The first mover by definition doesn’t possess potential. This is consistent with God, Who’s nature is pure Act. As such, He already possesses every perfection, so there’s no need for God to move from potential to actual. If the first mover needed something outside itself to move from potentiality to actuality, it wouldn’t be the first mover at all. If God doesn’t already possess every perfection, so that He doesn’t need to move from potentiality to actuality, He simply isn’t God, and we need to continue looking for the first mover that really is the first mover, for the god who is God.

Finally, Thomas doesn’t argue that everything moves, but that “some things” are in motion. Neither does he argue that everything is moved by something other than itself, but that “whatever’s in motion is put in motion by something else.” Being pure Act, God didn’t begin to move, so He wasn’t caused to move by something else.

Why does the first mover need to be God? Why can’t it be a force or energy in nature?

This objection confuses the conclusion of Thomas’ Argument from Motion. Thomas doesn’t argue that God is the first mover. Thomas argues that the first mover is God. It’s an important distinction. Thomas doesn’t start with God and move forward. Rather, he starts with what we can observe about the world -- “We see that some things are in motion” -- and moves backward to the cause of this motion. The cause of that motion is the first mover. We know that there must be a first mover, or there would be no motion at all. If, perhaps, we should discover that what we thought was the first mover is really only the next mover back in the series, and that there are movers beyond that one, we would dismiss such as the first mover and continue our search. If what we thought was God is put into motion by something other than itself, then it’s neither the first mover or God, and our search would have to continue.

Why can’t the first mover be a force or energy within nature? The first mover must stand at the beginning of the series of motion, for it’s the mover on which all other members in the series depend. Otherwise it, too, would be just one more member in the series. Clearly, a force or energy within nature can’t be the first mover, for then the universe would be the cause of it’s own existence. This would mean that the universe existed before it existed, which is absurd.

It’s important to understand that Thomas doesn’t pretend that the Five Ways prove the existence of God as the Judeo-Christian tradition understands Him, which is often a point of confusion for some who misunderstand his reasoning. What can be known about God by way of the Judeo-Christian tradition can only be known by revelation. The Five Ways demonstrates that one of the things that can be known about God by reason alone is that God exists. As for other attributes of God (ie: all-knowing, all-good, etc…), Thomas addresses those questions later in his Summa.

Newton’s First Law and Einstein’s Special Theory of Relativity disprove the First Way.

In his blog, “Rejection of Pascal’s Wager: A Skeptic’s Guide to Christianity,” (2000) Paul Tobin claims that Isaac Newton’s First Law of motion eliminates the need for a first mover. Newton’s First Law states that a body that is in motion or at rest will continue so unless acted on by an external force. Tobin takes this to mean that it’s as natural for a body to be in motion as it is for a body to be at rest. But, Tobin presumes too much. Newton merely describes that, whether or not a body is at rest or in motion, it won’t change unless it’s acted on by another force external to itself. Newton makes no claims at all about the natural state of a body, whether that’s at rest or in motion. Second, Newton’s First Law applies only to locomotion, movement from one place to another, and has no application at all on Thomas’ understanding of motion as change from potentiality to actuality. Finally, even in the case of locomotion, there’s still the question of what puts something in motion in the first place, or why the laws of physics exist, or why we can rely on such laws to hold firm.

Tobin also claims that Einstein’s Special Theory of Relativity disproves Thomas’ First Way, since Einstein showed that all movement is relative to other objects, and that no object serves as an absolute reference. An event that occurred at one time to one person could occur at another time to another. Again, Tobin makes the mistake of reading Thomas’ idea of motion as only locomotion and as requiring that a cause occur before its effect. Even still, since a thing’s actuality is always relative at least to it’s own previous potentiality, Thomas’ argument stands. Otherwise, we would have to claim that there’s no motion at all, a rejection of the first premise of the argument. Einstein doesn’t claim this.

Thomas’ Argument from Motion doesn’t stand up to modern physics.

In his analysis of Thomas’ First Way, “Assessment of the First Way” (2009), John Magee claims that modern physics puts the nail in the coffin of the First Way. “Some things,” Magee points out, “change of themselves through the exercise of intrinsic physical forces.” Magee explains that all physical changes and motion are caused by the four fundamental forces of gravity, electromagnetism and the strong and weak nuclear forces. As examples, Magee points to the movement of the planets as being the result of gravitational attraction and the bond between subatomic particles as being caused by the strong nuclear force. But, how does Magee account for the existence of the four fundamental forces in the first place? Why should we be able to rely on their consistent adherence to certain principles? Magee’s objection is just another way to say that the universe is the cause of its own existence, which we know is absurd.

Magee then claims that perceived changes in objects are really nothing more than the transformation of energy from one state to another, while the sum-total of mass-energy is conserved. This energy would have its ultimate origin in the Big Bang, which took place before today, so couldn’t be the cause of motion today, as Magee claims the First Way requires. But the First Way requires nothing of the sort. Ultimately, all causal series of motion find their origin in the first mover, regardless of when they took place chronologically. Also, the first mover exists outside of time, where all events are now, so regardless of whether an event took place millennia ago or just last minute, they take place at the present moment for the first mover.

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