The Argument from Efficient Causality:
We notice that some things cause other things to be (to begin to be, to continue to be, or both). For example, a man playing the piano is causing the music that we hear. If he stops, so does the music.
Now ask yourself: Are all things caused to exist by other things right now? Suppose they are. That is, suppose there is no Uncaused Being, no God. Then nothing could exist right now. For remember, on the no-God hypothesis, all things need a present cause outside of themselves in order to exist. So right now, all things, including all those things which are causing things to be, need a cause. They can give being only so long as they are given being. Everything that exists, therefore, on this hypothesis, stands in need of being caused to exist.
But caused by what? Beyond everything that is, there can only be nothing. But that is absurd: all of reality dependent—but dependent on nothing! The hypothesis that all being is caused, that there is no Uncaused Being, is absurd. So there must be something uncaused, something on which all things that need an efficient cause of being are dependent.
Existence is like a gift given from cause to effect. If there is no one who has the gift, the gift cannot be passed down the chain of receivers, however long or short the chain may be. If everyone has to borrow a certain book, but no one actually has it, then no one will ever get it. If there is no God who has existence by his own eternal nature, then the gift of existence cannot be passed down the chain of creatures and we can never get it. But we do get it; we exist. Therefore there must exist a God: an Uncaused Being who does not have to receive existence like us—and like every other link in the chain of receivers.
Question 1: Why do we need an uncaused cause? Why could there not simply be an endless series of things mutually keeping each other in being?
Reply: This is an attractive hypothesis. Think of a single drunk. He could probably not stand up alone. But a group of drunks, all of them mutually supporting each other, might stand. They might even make their way along the street. But notice: Given so many drunks, and given the steady ground beneath them, we can understand how their stumblings might cancel each other out, and how the group of them could remain (relatively) upright. We could not understand their remaining upright if the ground did not support them—if, for example, they were all suspended several feet above it. And of course, if there were no actual drunks, there would be nothing to understand.
This brings us to our argument. Things have got to exist in order to be mutually dependent; they cannot depend upon each other for their entire being, for then they would have to be, simultaneously, cause and effect of each other. A causes B, B causes C, and C causes A. That is absurd. The argument is trying to show why a world of caused causes can be given—or can be there—at all. And it simply points out: If this thing can exist only because something else is giving it existence, then there must exist something whose being is not a gift. Otherwise everything would need at the same time to be given being, but nothing (in addition to "everything") could exist to give it. And that means nothing would actually be.
Question 2: Why not have an endless series of caused causes stretching backward into the past? Then everything would be made actual and would actually be—even though their causes might no longer exist.
Reply: First, if the kalam argument (argument 6) is right, there could not exist an endless series of causes stretching backward into the past. But suppose that such a series could exist. The argument is not concerned about the past, and would work whether the past is finite or infinite. It is concerned with what exists right now.
Even as you read this, you are dependent on other things; you could not, right now, exist without them. Suppose there are seven such things. If these seven things did not exist, neither would you. Now suppose that all seven of them depend for their existence right now on still other things. Without these, the seven you now depend on would not exist—and neither would you. Imagine that the entire universe consists of you and the seven sustaining you. If there is nothing besides that universe of changing, dependent things, then the universe—and you as part of it—could not be. For everything that is would right now need to be given being but there would be nothing capable of giving it. And yet you are and it is. So there must in that case exist something besides the universe of dependent things—something not dependent as they are.
And if it must exist in that case, it must exist in this one. In our world there are surely more than seven things that need, right now, to be given being. But that need is not diminished by there being more than seven. As we imagine more and more of them—even an infinite number, if that were possible—we are simply expanding the set of beings that stand in need. And this need—for being, for existence—cannot be met from within the imagined set. But obviously it has been met, since contingent beings exist. Therefore there is a source of being, namely God, on which our material universe right now depends.
- Dr. Peter Kreeft