Ask a Thomist

What is an essentially ordered series of causes?

What’s the difference between an accidentally ordered series of causes and an essential ordered series?

By Matt Fradd

An accidentally ordered series of causes is one in which one independent object interacts with another independent object and causes it to move or change, similar to a series of dominos falling one after another. These changes take place over a period of time, whether short or long. Dye, for example, is applied to hair, and after a few minutes it changes color. A man drinks several beers and is eventually drunk. What all these changes have in common is that the past parts of the series do not directly affect the future parts. You can throw away the hair dye bottle and the cans of beer, but you’ll still be a drunk person with blue hair.

An essentially ordered series of causes, on the other hand, occurs when the motion or change in the series is dependent on every past member in the series. For example, imagine Thomas Aquinas’s great works are sitting on a table. These books can be positioned as they are because there is a table underneath them. The table, in turn, is able to hold the books because the floor supports it. But the floor rests on a foundation that lies on the earth and so on and so on. Everything in the series is essential to the end result: or the book sitting on the table. If you took away the table, the book would not be sitting on it. If the house no longer had a foundation, then the floor, the table, and even the books would ultimately collapse.

Another example would be a series of gears. In an accidentally ordered series, like a set of dominoes, the previous members of the series could be removed or destroyed and not effect the motion in the latter part of the series. But in an essentially ordered series like a set of gears, any tampering with a previous member stops the whole series from changing. If you remove any of the past gears in the series, every other gear will stop turning as well.

Examining a hierarchical series helps us to see God as the First Mover. When we consider a series of causes that all exist at the same time, we immediately recognize that something holds the series together. The earth holds the foundation of the house, but, who holds the earth? “Gravity,” we might answer. But, what keeps gravity in existence? Eventually, in every hierarchical series, we trace all the causes back to a first cause, a power that supports and holds everything together in existence, or what Thomas calls God.

We know Thomas is describing an essentially ordered causal series because of the examples he uses. For example, in his explanation of the argument from causality he says 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.”[1]

An infinitely long series cannot explain the motion of the staff because adding members to the series, even an infinite number of them, does not explain why there is any motion in the first place. As Garrigou Lagrange once quipped, “To do away with a supreme cause is to claim that, as someone has said, ‘a brush will paint by itself provided it has a very long handle.’”[2]

[1] ST, I, q. 2, a. 3
[2] Reginald Garrigou-Lagrange. God: His Existence and Nature Vol. 1 (New York: Herder Book Co., 1934) 265.


Matt Fradd speaks to tens of thousands of people every year. He is the best-selling author of several books, including Does God Exist?: A Socratic Dialog on the Five Ways of Thomas Aquinas and The Porn Myth: Exposing the Reality Behind the Fantasy of Pornography. Matt earned his master’s and undergraduate degree’s in philosophy from Holy Apostles College. His podcasts, Love People Use Things and Pints With Aquinas are listened to by tens of thousands of people every month. Matt lives with his wife, Cameron, and their children in Georgia.

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