Christian apologists—defenders of the Christian faith—have used a number of arguments in order to demonstrate the rationality of belief in God. One of the most popular of these is the cosmological argument, which defends the existence of God on the basis of cause and effect. Since every effect must have a cause, there must be one cause that started everything. One eternally existing cause set everything in motion, creating effects that then caused other effects that then caused other effects and so on. This eternally existing cause is God.
We have already seen that chance cannot be this cause because chance has no causal power. The universe’s self-creation is likewise impossible because something cannot come from nothing. Confronted by this dilemma, some have persisted in denying the existence of God by denying the reality of cause and effect itself.
The work of philosopher David Hume is often cited to justify the denial of cause and effect. Hume used the illustration of the pool table to argue that we cannot know for certain which causes produce which effects. Although we strike a cue ball with a pool stick, he said, we cannot prove that the striking of the ball with the stick makes the ball move. All we have seen for certain is a relationship of contiguity—a relationship where one event follows after another. We may assume that the stick made the ball move, but we cannot be certain of that. It could be that an unseen force actually caused the movement. Hume’s thinking here can lead to a radical skepticism, and as Christians we say that the unseen force of God’s decree, the pool stick, the player’s movement of the stick, and perhaps something else all made the ball move. In any case, Hume was not denying cause and effect outright; he just believed we cannot identify causes with certainty.
The law of causality is one of those axioms that is indisputable. Every effect must have a cause, for an effect, by definition, is something that is caused. Thus, for anything to exist, an uncaused something—or someone—must exist. This “uncaused cause,” as it were, must have the power of being in itself and must be the first, primary cause of everything else. It must depend on nothing else. It must not be an effect, for if it is an effect of something else, it cannot be the very first cause that brought everything into existence. Nothing created qualifies as this first, primary cause. Only God, the eternal Creator, can be the reason why there is something rather than nothing.