Support: Intuitively true, and true in our experience. Things don't just pop into existence uncaused out of nothing, lest you propose the existence of magic. But in fact this would be even worse than magic, for at least magic has the "cause" of the magician waving a wand. If it were false then why doesn't anything and everything just pop into existence? Why only universes? Why is “nothing” so discriminating? Why aren't universes popping into existence all the time? Since they aren't, there must be some limiting factor, and a limiting factor can only operate if there is a cause to limit.
Objection: There is no a priori reason why it should be true. According to Hume, if we can imagine something coming into existence from nothing then it is not logically incoherent and thus at least possible. Response is that just because we don't have an a prior reason it does not refute the premise and that Hume went on to say that he does accept the causal principle. Just because we can imagine a horse popping into existence uncaused does not mean that we think this is actually possible.
Objection: If true, then it would apply to God as well. God can't have begun to exist without a cause. God can't be infinite. If God is timeless, then this is a mystery. And denial of the premise is preferable to acceptance of theism, which makes even less sense. Response is that it's true that God did not begin to exist and that he can't be infinite. But he can be external to time and in fact under Kalam he would have to be. Just because this is mysterious does not refute it.
Objection: It can be true of things in the universe, but not of the universe itself. Response is that the causal principle is a metaphysical principle, not a physical one. Being cannot come from non-being.
Objection: Virtual particles pop into existence uncaused from nothing. Response is that these may not be indeterminate; physicists are still looking for why they pop into existence and some do not like the apparently indeterminate nature. Also, they do not come from nothing but from a rich field of energy in the vacuum.
Objection: Alexander Vilenkin's quantum creation model says that a universe with a very small radius, even zero, can undergo quantum tunneling and lead to expansion, thus getting a universe out of (almost) nothing. Response is that even a radius with a measurement of zero is not the same as having no radius at all, as in the case with nothingness. Volenkin's model is still a step from something to something, not nothing to something.
2. The universe began to exist
Support #1: An actual infinite cannot exist. Hilbert's Hotel shows the logical contradictions that can occur in an actual infinite.
Objection: Cantor legitimized the idea of actual infinites. Response is that this is only a mathematical model and does not represent the ability of an actual infinite to exist in the real world.
Objection: Yes, the Hilbert's Hotel paradoxes would happen and are exactly what we would expect in an actual infinite. Response is that yes, the paradoxes would happen and would be logical absurdities and thus cannot exist in the same way a square circle cannot exist.
Support #2: You can't traverse an infinite. A beginningless series of events would equate to an infinite number in the past, and so to get to today you would have had to go through an infinite amount of time, which impossible.
Objection: It's a logical trick, like Zeno's Paradoxes, which also claim the inability to traverse an infinite. Response is that saying there could have been a beginningless series of events is like saying that you just wrote down all negative numbers, ending at zero.
Support #3: Scientific evidence from cosmological models.
1. Standard model: Space-time, matter, laws all originated in a singularity.
2. Steady-state models: Expansion is balanced by creation of new matter. No experimental verification, the microwave background radiation confirms Big Bang, and production of light elements (H, He, etc) could only happen in the Big Bang.
3. Oscillating models: Big Bang, expansion slows and reverses, Big Crunch and then new Big Bang. Hawking-Penrose singularity theorem shows a singularity at the Big Bang through which no spacetime trajectory (like from the previous collapsing universe) could pass, there are no known physics that would allow a bounce back, and there is not enough mass in the universe to halt and reverse expansion, and the expansion is actually increasing.
4. Vacuum fluctuation models: Virtual particles pop into existence from the pre-existing vacuum, and the universe may be one such particle. If the vacuum was pre-existing from eternity, then given this infinite time an infinite number of these universes would exist and have merged together, and we observe no evidence for this.
5. Chaotic inflation: There is a wider universe that will always be inflating, and our universe is one of many bubbles in this wider universe being forced to expand by the wider expansion; proposed to expand forever, but Linde proposed that it was infinite in the past as well. Cannot be infinite into the past and thus, still needs a singularity, and Linde now agrees
6. Quantum gravity models: Hawking uses imaginary numbers which gets rid of the singularity, and replaces it with a beginning that has no definite point. Imaginary numbers are a good trick but they do not respond to real life, and so to reflect reality the imaginary numbers need to be swapped out with real numbers again in which case the singularity reappears.
7. Pre-Big Bang models (string theory): Our universe emerges from a black hole in an infinitely existing vacuum. The infinitely existing vacuum would lead to an infinite number of universes, all merged, which we don't see.
8. Ekpyrotic models (string theory): Two large M-branes (branes) collide and cause the Big Bang, and is cyclic. The model is new, and there are problems with it, but the biggest issue comes back to the need for a singularity at some point
9. Borde-Guth-Valenkin Theorem: Proved that no matter what model turns out to be correct, the past cannot be infinite and there must be a singularity and an absolute beginning.
Support #4: The Second Law of Thermodynamics says that within a closed system, everything will tend toward a state of equilibrium and complete rest (entropy).
1. Cosmological implications: If an infinite past, then the heat death of the universe should have happened by now. Boltzmann's theory is that everything is at complete rest but some sections undergo spontaneous fluctuations of energy, and our universe is one of those. But we should be observing a much smaller area of energy than our own universe; thus it would be much more likely that we would either have a small universe or that only one person would exist, i.e. solipsism.
2. Eschatological scenarios: If enough matter exists, the universe will stop expanding and begin collapsing. However, there is not enough matter and so the universe will expand forever, dying a heat death. This confirms that the past cannot be infinite because otherwise we should be in a universe that has already died.
3. Oscillating models: Oscillating universe models may avoid entropy. But it was discovered that entropy actually carries over into the next cycle, so given an infinite past, the heat death of the universe still would have happened by now.
4. Baby universe: The idea that black holes give birth to new universes, and ours is one. Hawking came up with this idea, but quantum physics has shown that information must stay within a black hole and so they cannot give "birth" to a new universe on the "other side." Hawking placed a bet about them and admitted he lost.
5. Inflationary multiverse: Our universe is but one bubble of spontaneous energy fluctuation on an ever expanding region of an eternal universe that has already died a heat death. Suffers from the same problem as #1: we should be observing a much smaller region, or most likely just your own mind.
3. Therefore, the universe has a cause
Support: From 1 and 2.
The Nature of the cause was spaceless, timeless, non-physical, supernatural, and personal
Support: The cause was external to and the cause of all space, time, matter, and the laws of nature, and so therefore must be spaceless, timeless, non-physical, and supernatural. It also must be personal, for the following reasons:
1. Scientific vs personal explanations: There are two types of explanations, physical and personal: the tea can be described as boiling due to the 212 degree heat applied to the bottom of the teapot, or it can be described as boiling due to someone wanting to make tea. The first one is a physical explanation, but the cause of the universe was external to the laws of physics and so the cause cannot be physical. Therefore it was personal.
2. Two types of non-physical objects: The cause must be spaceless, timeless, and non-physical, but there are only two types of objects that fit that description: abstract objects (like numbers), and minds. But abstract objects cannot cause anything, so therefore the cause must be a mind.
3. Timeless cause would lead to timeless effect: If the cause were impersonal and "eternally" existing (timeless), then the cause's effect would be eternal as well. But the universe began to exist a finite time ago and so therefore the cause must be the willful volition of a personal agent.
Objection: The word "cause" is being used two different ways: to mean the re-arrangement of existing matter (as we usually mean), or creation ex nihilo (which we have no experience of). Thus, the argument is guilty of equivocation. Response is that "cause" is being used to describe something that brings about an effect, so whether its ex nihilo or not is irrelevant.
Objection: The argument does not conclude that the cause is personal. Response is that this is a supplementary examination of the first cause, but not part of the argument proper.
Objection: The argument does not argue for one cause vs multiple causes. Response is that there is no need to postulate more than one cause.
Objection: A first cause is logically compatible with an infinite past. Response is that the argument argues for the impossibility of an infinite past, regardless of any cause or not.
Objection: If everything has a cause, then the first cause must have a cause. Response is that the argument says that everything that begins to exist has a cause, not that everything has a cause. Not special pleading for God since the atheist has maintained the existence of an infinitely old universe.
Objection: Creation ex nihilo is incomprehensible, so it is irrational to believe in it. Response is that this is equivocation of the term "incomprehensible," which can mean either gibberish (as this objection defines it) or a proposition that is clear but we don't understand the mechanics. Since the argument is about the first cause, then clearly it isn't gibberish because we are discussing it actively and so the second meaning of "incomprehensible" is the correct one. Also by the same rationale, it would be even more incomprehensible that the universe popped into existence uncaused out of nothing.
Objection: The cause of the Big Bang can be neither before it (since time did not exist) nor after it (since backward causation is impossible). Response is that this is a false dilemma. The cause can be simultaneous with the Big Bang. As God is timeless, he can represent a boundary to time that is causally but not temporally connected with time.