Often people ask: “If God created everything, then who created God?” Of course no one created God. For if God was created, He’d be a creature (created), and so He wouldn’t be God. His creator would be God. But then who created His creator? If He too was created, then He isn’t God, but a creature of God.
To be God is to be the creator of all creatures. So God is not Himself a creature. He is uncreated. He always existed. He cannot not exist. And so He did not come into existence, nor will He go out of existence.
But I can’t imagine that! How is that possible? It is true that you and I cannot imagine that. For everything in our experience has had a beginning. And our imagination is limited to what can be imagined, and what can be imagined are material things and their movements.
Material things have a beginning, a middle, and an end. But God is not a material and created thing. And so He cannot be imagined. And as for your second question (How is that possible?), it is impossible for it to be any other way. There must be a First, uncreated and uncaused cause of all other things. Let me go over a concept first employed by Aristotle and later developed by St. Thomas Aquinas, the proof from motion.
St. Thomas begins by pointing out that nothing moves itself from potency to act, except by something already in act. For instance, a piece of chalk on a slate will not move itself to another position on the slate except by something already in the act of motion. The piece of chalk is actually stationary, but potentially moving. It is potentially in another place on the slate. In order for the chalk to acquire that new position, it will have to be moved to that new position by something already moving.
Another way of putting this is to say that ‘nothing can give to itself what it does not possess’. If the piece of chalk is at rest, it is not moving. It does not have motion. If it does not have motion, it cannot give itself motion. It must receive motion from another that is actually moving. Note: Living things do not move themselves in a primary way. A living thing, as a whole, does not move itself from potency to act. Rather, one part moves another part, and in this way the whole thing moves.
Now, St. Thomas points out that there cannot be an infinite or unlimited series of causes. Consider the arrow above. The arrow is finite. When it moves, it moves a finite distance in a finite time. But if the arrow was infinite, it would move an infinite distance in an infinite time. Every movement of it would cover an infinite distance, and every movement would occur in an infinite duration of time. Moreover, an arrow that is infinite could not acquire more distance. It would not have the potentiality to move further ahead of itself.
Consider now the series of movers in color above. The red ball (extreme left) is moved by the green, but the green in turn received its motion from the blue ball, and the blue ball received its motion from the purple (fourth from the left), etc.,. The red ball on the left could represent anything, such as a dry leaf blowing in the wind that comes to rest at your feet on a fall day. The motion has come to an end, the leaf is at rest next to your left foot.
Hence, its movement is terminated. It has come to an end. It is finished, or finite. If the series of causes preceding the motion of the leaf is infinite, then the motion of the leaf or red ball on the left would never be terminated (finished, finite). The leaf moved by virtue of the motion of certain atoms in the air, and those in turn are moving by virtue of the motion of something else, etc. The series must be finite. Why? Because the motion of the leaf came to an end (finished).
First, if the series of movers were infinite, the series would stretch back to infinity. Now, since all the things moved and moving are necessarily bodies, they must form a single moving object, the parts of which are in contiguity (in contact, or touching) or continuity. But if the whole single series is infinite, then when it moves, it moves an infinite distance in an infinite time. But it is impossible to move an infinite distance.
Think about this for a moment. To move is to acquire something, such as a new location. But an infinitely long stick, for example, cannot move forward to acquire a new location, since it covers an infinity. There is nothing ahead of it to acquire, for it occupies every location ahead of it.
But the red ball has moved a finite distance and its movement has terminated. It moved a finite distance in a finite time. No matter how long the series preceding it is, if it is finite, it moves a finite distance in a finite time. But if it is infinitely long, it moves an infinite distance in an infinite time. But this is absurd. The very fact that the motion of the leaf has come to an end shows that the series is finite.
A Series of Essentially Subordinated Movers
Let’s consider this from another angle. There are two types of series of movers. The one is a series of essentially subordinated movers. The other is a series of accidentally subordinated movers. Let’s take the latter first. In a series of movers that are only accidentally subordinated to one another, an actual infinity is possible.
For example, a chicken comes from an egg, an egg from another chicken, and the other chicken from still another egg. There is no reason why such a series, stretching backward through the past, cannot be unending. In this kind of a series, the movers are operating in succession, not together. And so a parent chicken need not be here and now influencing the hatching of an egg. It may in fact be dead.
This is not the kind of series St. Thomas is referring to. He is referring to a series of essentially subordinated movers. In movers essentially subordinated to each other, one mover is here and now influencing another, like the hand moving a piece of chalk. Without the causality of the first, there is no movement in the second.
Note the color series above. This represents a series of essentially subordinated movers. A series of essentially subordinated movers cannot be infinite for the reasons given above. Treating it as a single thing, it would cover an infinite distance in an infinite time.
Also, the red ball received its act of motion from the green, which in turn receives its act of motion from the blue, and so on. If this “and so on” proceeds ad infinitum, then the red ball will never receive the act of motion. The red ball is moved by the green, the green receives its actual movement from the blue, etc. The moved effect and the mover, in any motion, are simultaneous. The hand moves the stick, which moves the eraser on the slate, which moves the chalk on the slate, and as soon as the hand stops moving the stick, the stick stops being moved. When the carpenter stops bulding the house, the house stops being built.
Now, yellow moves teal, and teal moves red, and red moves brown, and brown moves green, and as soon as yellow stops moving, teal ceases to be moved. If teal moves red, then as soon as teal stops being moved by yellow, red stops being moved by teal. In a series of movers, however long, all of the members must be operating in some kind of simultaneity. As strictly physical and hence dependent on quantity, our series of causes must be stretched out so that one is outside the other, like the stick that is touched by the hand and in turn touches the eraser.
Physical causes are in contiguity with each other. Now whatever is quantified is hemmed into itself and cannot influence other things without contacting them directly or through a quantitative medium. An infinite series of physical causes, one placed outside another, would fill an infinity of space.
But finite causes cannot be strung together to form an infinity. Number is only potentially infinite, not actually infinite (there is no actually infinite number). And more, if our series of physical causes were truly infinite, the causality would take an infinite time to “pass” through it from one member to another into infinity. Hence, the leaf would not move, or the red ball would not move. In fact, no thing on the series would move, if it is preceded by an infinite series.
Hence, the series must be finite. It follows that there must be a First Mover. But this First Mover must be unmoved, otherwise we are back to positing preceding causes. But this cannot go on to infinity, so there must be a First Unmoved Mover, if anything in the universe moves.
Now, since motion is an act that is received by something potentially moving (but actually stationary), the Unmoved Mover must have no potentiality to receive anything, but can impart the act of motion. As we will see later, this can only mean that the Unmoved Mover is God, who is Pure Act, without any admixture of potentiality.
We can even look at this vertically (below):
Why is it that if the series (green “causes”) was infinite, the meteor would never have been moved? Because the cause of its motion, i.e., another meteor (the green “cause” just above it), would never have been moved. The reason is that it would take an infinity to move the meteor. The series prior to it is infinitely long, and the causes would churn for infinity. The effect would never reach the meteor.