As formulated by Thomas Aquinas, the uncaused cause argument is stated as follows:
- "Nothing is caused by itself. Every effect has a prior cause. This leads to a regress. This has to be terminated by a first cause, which we call God."
Many of the responses to the Unmoved mover argument also apply to this one:
One can argue that the conclusion "God is the first cause" contradicts the premise "everything has a cause", and that the first cause argument is therefore self-contradictory.
It can, however, be restated as a reductio ad absurdum, to make the contradiction a desirable feature:
- Premise: every event has a cause.
- Premise: there can be no infinite regress.
- Premise: there exists some event e0.
- From (1) and (3), it follows that e0 has a cause e1, which in turn has a cause e2, and so on, in an infinite regress.
- From (2) we know that there can be no infinite regress, which contradicts (4).
- Therefore, at least one of the premises must be false.
If we reject premise 1, that every event has a cause, then there must be at least one uncaused cause, which can be called "God".
Why call it God?
- See also: Which god?
Even if we accept the argument from first cause, the conclusion is still problematic: the word "God" carries a lot of undesirable cultural baggage, denoting an intelligent being. If the ultimate cause of our universe turns out to be, say, a random vacuum fluctuation, then that would be "God" by Aquinas's definition, but to call this phenomenon "God" would be misleading. It also can be noted that if for some reason there did have to be a first cause, we don't know what it was or enough about it to give it attributes other than being the first cause, which would make calling it and assuming it is God an argument from incredulity or the "God of the gaps" idea.
Argument from incredulity
To say that because we currently observe cause and effect relationships occurring in space-time, the universe itself must have had a first cause is assuming something that no one knows. Before the big bang time and causality could not be said to exist at least in the way that we perceive it, and so to make assumptions about the behavior of matter prior to time is pure speculation. Simply because one cannot conceive of something happening without a cause, does not mean that we can assume everything needs a cause. The logic fails as soon as we attempt to precede the Planck time, after which nothing can accurately be said about the relationship of cause and effect. It is much the same as saying that order and design must mean there was a designer, just because as far as you can tell this is the case with things that humans design. You are saying you cannot fathom a natural process that would explain what you are trying to explain and so you assume that nature must abide by your narrow understanding of order and design. One's narrow understanding of cause and effect based on their current concept of time does not mean that before time was as it is today their narrow views still apply.
- Who created God?
- Pairs of virtual particles are created (and annihilated) all of the time, in vacuum, out of literally nothing, with no prior cause. This contradicts Aquinas’s premise. (Whether this is a valid counterargument is debatable. The Casimir effect is poorly understood; it is nondeterministic but statistically predictable. If this is a valid counterargument, then you could equally say that the fact that your coin flip turned up heads rather than tails is also a valid counterargument.)
- Even if there is an infinite regress of causes, so what? The human mind is uncomfortable with the concept of infinity, but reality has no obligation to make us comfortable.
- If they claim that with an infinite past, we could never get to now, flip the infinity: Does an infinity of seconds not stretch forward into the future, eternally? Starting from an infinite future, can you go a second before that, and a second before that, ad infinitum, and get to now?
- It is simpler to assume that matter and energy are infinite (as neither can be created or destroyed), than to assume that a god that created them is infinite. (See Occam's razor)
- This argument is also using the fallacy of composition. Since one (or all, or any number) of parts need a cause inside the universe, and then applying this to the universe as a whole is simply a fallacy.