Here's my opening statement in a debate I was in on debate.org. The resolution was The Kalam Cosmological Argument is unsound. I was Con. This turned out to be an interesting debate because instead of attacking the argument the usual ways, my opponent attacked the whole notions of a priori knowledge and inductive reasoning. So the debate turned out to be mostly over epistemology.
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Another KCA debate. Yay!
Preliminaries
Pro defined God as "the personal originator of all that exists." Since God could not have created himself, I want to tweak this definition to say, "the personal originator of the universe."
1. Everything that has a beginning of its existence has a cause of its existence.
The meaning of the first premise
Most things that begin to exist do so ex materia, but the KCA is more interested in beginning ex-nihilo. Although this first premise refers to both, I think we should focus on beginning ex-nihilo, though I'll briefly defend the more general principle.
There are two types of causes. A material cause is the material out of which an object is made, and an efficient cause is whatever brings about the change. For example, if I carve a bowl out of a piece of wood, the wood is the material cause, and I am the efficient cause.
I take the first premise to mean that whatever begins to exist has a cause, either of one kind or another. It doesn't specify which kind of cause each thing must have. This is relevant because the typical counter-examples that are raised against the first premise include pair production and radio active decay. According to some interpretations of quantum physics, these events entail the beginning of certain particles without efficient causes. However, these events do havematerial causes, so they are not counter-examples of the general principle.
If the first premise were tweaked to refer only to things which begin to exist apart from material causes, then the cause would have to be efficient. In that case, even if virtual particles begin to exist without efficient causes, they would still not serve as counter-examples since the tweaked first premise excludes them from its field of reference.
a priori defense
There are things we grasp by a rational intuition. For example, if two straight lines intersect, the opposite angles will be equal. We don't have to experiment to discover this to be universally true. We only need to grasp it. But not all things that can be known by rational intuition are known by all people. For example, some people rationally grasp why the Pathagorean theorem is necessarily true, but other people just memorize it and trust their math teacher.
The notion that it's impossible for something to spontaneously come into existence uncaused out of nothing is part of our rational intuition. One need only explore the idea in their minds to grasp that this is a necessary truth. It could be that the reason some people don't accept this premise is because, just like the case of the Pathagorean theorem, they can't "see" it. But that is no reason for those of us who do grasp it to have any doubts. This is something we can know with certainty.
If it were possible for something to spontaneously come into existence uncaused out of nothing, then there would have to be a potential or a probability that something could come out of nothing. Probabilities depend on initial conditions, so that would mean 'nothing' had properties. To have properties is to exist, so it would mean 'nothing' is actually 'something,' which is a contradiction.
a posteriori defense
Science is driven by a desire to know why things happen the way they do. When we observe something in the world, we want to know what caused it. With time and effort, we often are able to discover the cause. So we can inductively infer that there are causes to all events--even the ones whose causes we have yet to discover.
Most physicists subscribe to indeterministic interpretations of quantum physics, which entail undetermined events, such as radio active decay and pair production/annihilation. But it is a mistake to infer that because an event is indeterminate that it is therefore uncaused because indeterminate events have probabilities. The probabilities are determined by initial conditions, so those initial conditions serve as causes, albeit insufficient causes. Sufficient causes entail 100% probability in their effects, but insufficient causes entail less than 100% probability of their effects. The fact that particular isotopes have fixed half lives shows that radioactive decay is not completely a-causal.
2. The universe has a beginning of its existence.
The meaning of the second premise
For this debate, I'll define the universe as the sum total of all space, time, and energy. If there is a multi-verse, then it is included in "universe."
Usually, when something begins, it is preceded by a time in which it didn't exist. However, the universe could not have been preceded by such a time since time itself had a beginning. There could not have been a time before time in which time didn't exist because that's a contradiction. We must mean something different when we say the universe began to exist than when we say most other things began to exist.
What we mean, essentially, is that the universe has a finite past, and there is no state of affairs in which the universe exists timelessly.
The impossibility of forming an infinite set by successive addition
1. If the past had no beginning, it would be composed of an actually infinite collection of equal intervals of time.
2. An actually infinite collection of equal intervals of time cannot be formed by successive addition.
3. The past was formed by successive addition.
4. Therefore, the past cannot be an actually infinite collection of equal intervals of time. (from 2 and 3)
5. Therefore, the past had a beginning. (from 1 and 4)
I think the only controversial premise is 2. The reason the second premise is true is because there are no two finite numbers that you could add and reach infinity. The sum of any two finite numbers is always another finite number.
The grim reaper paradox
Suppose that time had no beginning and that during each hour in the past, a grim reaper (GR) was created and set to kill you at 12pm + 1/n minutes, where 'n' is the number of the reaper.. If you are alive when a GR goes off, it will kill you instantly, but if you are already dead, it will do nothing. With this set up, there is no first GR because each GR has a GR before it. It follows that no GR can kill you, yet you can't survive a moment past noon. Therein lies the paradox. If the past is beginningless, then the GR scenario would be possible, but since it's not possible, the past must have a beginning.
3. The universe has a cause of its existence.
This follows from 1 and 2.
4. If the universe has a cause of its existence then that cause is God.
Since we are defining God as "the personal originator of the universe," and since we have already argued that the universe had an originator, all that remains is to show that the originator is a person. For the purpose of this debate, I'll define a person roughly as a mind.
Nothing can create itself, so the cause of the universe must be other than the universe. Since the universe is the sum total of space, time, and energy, the cause of the universe must be spaceless, timeless, and immaterial.
Disjunctive argument from minds and abstract objects
The only things that could have such properties are abstract entities (e.g. numbers, propositions, etc.) and minds. Since abstract entities do not stand in causal relations, the cause of the universe must be a mind, which means it's a person.
Only minds can create ex nihilo
When we act on purpose, a mental event causes the action. My intention to type is the reason my fingers move. Only substances have causal powers, and my mind has causal influence over my brain, so my mind is a distinct substance from my brain. It is an immaterial substance.
When a particle at rest begins to move, it has kinetic energy that it did not have before. That energy has to come from somewhere. Since minds are not composed of energy, the only way they can have causal influence in the world is by creating energy ex nihilo.
Since minds are the only entities known to have this ability, the best explanation for the beginning of the universe is a very powerful mind.
Therefore, God exists
This follows from 3 and 4.
