I have been always interested in many philosophical arguments, including almost everything that has to do with existential questions, especially many theological arguments. Most common theological arguments I have seen are very old and very weak, and keep being rehashed to try and come up with harder to refute formulations. One argument I have only started seeing in the last few years seems to pick up some steam lately. It goes like this:
1. The law of conservation of energy states that "Energy can neither be created nor destroyed". Energy can be transformed into matter and vice versa, or changed into another form of energy.
2. The Big Bang Theory states that the universe did not exist before the Big Bang.
3. The Universe currently has energy (in the form of matter and various forms of energy).
4. Therefore the universe came to existence through some supernatural process.
5. They then conclude that the universe is created by an agent (or in some cases just that the universe if more consistent with one that is created by an agent than with one that isn't).
It seems this argument is responding to the growingly vocal scientists that push the idea that the universe may have come into existence from nothing. As long as the said scientists are only talking about a possibility and not claiming that the universe actually spontaneously sprung into existence from nothing (if they did, they would have to produce real empirical evidence), I do not see what anyone can object in the current state of knowledge. In the above argument, however, I see a large number of flaws and hidden unwarranted assumptions.
Conservation of energy and the Uncertainty Principle
The first serious issue with the argument is that the law of conservation of energy only applies to measured energy quantities. The Heisenberg's Uncertainty Principle shows that energy is not always conserved, but if we measure the energy of a system at any two moments, then the law of conservation of energy applies between the two measures. During the time between the measures, the energy can fluctuate by any quantity as long as it only does so during intervals that are inversely proportional to the fluctuation. Stated differently, the energy can increase by large amounts, as long as it does so for an interval of time small enough. To get any measure of any precision, the measure itself must span an interval of time. It so happens that the interval of time where the energy of a system can have a variation of some value is smaller than the interval of time required to measure that energy with a precision smaller than the value of the variation, thus any such variation is not measurable. However, that variation can have other effects that may and have been detected.
There is empirical evidence that in a vacuum (empty space), particles do actually pop in and out of existence all the time (there appearance as well as their disappearance are both violations of the law of conservation of energy).
Now, if the fluctuation created for a short period of time some positive energy, and another fluctuation created an equal amount of negative energy with the short time, the total energy would be zero, and the initial fluctuation could be caused to not cancel out. Although speculative, this scenario is not in violation of physical laws. Something could be created from nothing, as long as all conserved quantities including energy are still equal to zero.
Conservation of energy and isolated systems
When we say that "Energy can neither be created nor destroyed", all we are saying is that any increase in the energy of a system has to come from the exterior of the system, and that any decrease has to be transferred to the exterior of the system.
If the system is isolated (has no interaction with the exterior of the system), then we can state that the total energy remains constant.
So, do we know that the universe is isolated? It depends on the definition of the Universe.
If what we mean by the universe is "all of space-time and all its contents", then the answer is that "in the current state of knowledge, it is isolated". The lack of knowledge about the conditions at the beginning of time (i.e. in the infinitesimally small fractions of a second following the Big Bang) does not allow us to actually fully answer the question, as there could have been interactions with something external in the time between the Big Bang and one millionth of a millionth of a second afterward.
Since the argument is dealing exactly with what happened at the moment of the Big Bang, one can postulate nothing about the universe being isolated. It may be counter-intuitive, as our intuition cannot guide us when time is not there, nor in dealing with the nothing of something external to space and time. However, there is no fundamental law, nor is it probable that reality has to be intuitive. Actually, we do know of aspects of reality that are counter-intuitive, especially the whole set of Quantum phenomena.
Even if the law of conservation of energy is applicable, we do not know if it would mean that there could be no increase in the energy of the Universe, as long as we do not have evidence that we are only considering conditions in which the universe is an isolated system.
What would be external to the Universe? Well, the current state of knowledge does not provide any answer, but many speculative ideas can be proposed. One of the prevalent hypotheses about the early universe is "Cosmic Inflation", which is supported by many observations, even though more empirical evidence is still needed for it to reach the full status of a scientific theory. If there was a Cosmic Inflation, then it is highly probable that our universe is not the only one, and Universes would be springing into existence all the time. This idea about a "Multiverse" composed of many universes could also result from other hypotheses if they are true. Though very speculative at the moment, this idea is one way there could be "something" outside of the universe.
Many have tried to use recursion to say that if there is something external to the universe, one could just take whatever the whole including the universe and whatever is outside of it, and apply the same "conservation of energy" argument. The problem is that we have no knowledge if such a whole would have a beginning at all.
Does the Big Bang Theory say "The universe did not exist before the Big Bang"?
Actually, the Big Bang theory states that space-time started at the Big Bang. It is not just semantics to say that it does not state "the universe did not exist before the Big Bang", as there is no such thing as "Before the Big Bang", since time did not exist.
Trying to discuss what caused the "Big Bang" may simply make no sense, as causality (at least the common meaning of the term) requires time.
Note:
I have heard some people argue that time may not have an actual starting point, and the beginning of time could be asymptotic when we get close to the Big Bang. I have all kind of issues with this idea, including:
• To speak of an asymptote, we need at least two dimensions. The idea speaks of time having an asymptotic behavior in time. This requires time to have at least two dimensions, one of which would be asymptotic relative to the other. Unless this can be formulated clearly (including what these time dimensions are), the idea is just nonsense.
• For this idea to have any explanatory power about the early time after the Big Bang, there should be some refinement of the Big Bang theory, which is neither called for by any empirical evidence, nor proposed in any well formulated hypothesis. The Big Bang theory is based on the expansion of the universe, and if there is no change in physical law during the whole existence of time, then the universe would have been a single point at a certain moment in time. If the time dimension in this formulation is the one that is asymptotic relative to whatever other dimension, then the time dimension would not have a starting point and there would be no need for a Big Bang. If on the other hand, the time dimension in the formulation of the big bang theory is the one relative to which some other dimension is asymptotic, the asymptotic nature of this hypothetical dimension has no relevance to the argument.
The Universe currently has energy
This statement is actually a bad formulation. Energy is a quantity that can be positive, negative or zero. It is not a property that can either be present or absent.
A correct formulation of what is intended, as far as I can tell, is "The Universe currently has a non-zero energy". How do we know that?
It is not sufficient to say that since there is matter, and there are measurable energy quantities in the universe, the total energy would somehow necessarily be non-negative… one would still need to be able to either measure all components of the total energy and show that they add up to a non-zero quantity, or have a way to measure the total energy and show that it is not zero. I have seen different arguments, but most of the attempts I have seen center around determining the energy density at large enough scales so that it is homogeneous throughout the universe, and then integrating the energy density (taking into consideration that the measured curvature of space is very close to that of a flat universe). Many of these attempts result in a total energy of the universe being zero or undefined (as in the case if the universe is infinite).
Although I do not master the physics involved, it is quite clear to me that there is no agreement that the total energy in the universe would be non-zero.
The premise that the Universe has non-zero energy is not substantiated at all. That alone renders the argument completely moot.
"The universe came to existence through a supernatural process"
Such a statement is simply not scientific. If a scientist encounters evidence that cannot be explained by our understanding of reality (or of nature), he would not hypothesize that some supernatural process is involved. He would instead try to refine our understanding of nature (refining laws of physics that pose a problem).
Although this is a bias, as the scientist would not be open to any supernatural explanation of anything, the argument is trying to use science to prove a point, and therefore must abide by the methods of science. If the methods of science are not accepted, then there can be no substantiation to any of the premises. If they are accepted, then even if the first three premises were true, it would just show a limitation in current theories including the involved laws of physics, and definitely not any involvement of anything supernatural.
From "Supernatural Process" To "Created by an Agent"
I simply do not see how one can make such an inference. Going from a process to an agent requires going into what the process is (or at least what it is likely to be).
Summary of the main hidden assumptions
Assumption 1: The Universe is an isolated system
Even if the universe was shown to have a non-zero total energy, and it came to existence at the Big Bang, if the universe is not an isolated system, all one can say it that there must be a decrease in the energy that resides outside of the universe at the moment of the Big Bang.
Assumption 2: The total energy of the universe is currently non-zero
Even if the Universe was an isolated system, came to existence at the Big Bang, and the law of conservation of energy was applicable at the moment of the Big Bang, if the total energy of the universe was currently zero, then the universe could just have come out from nothing without violating the law of conservation of energy (Many other aspects would still need to be explained, but at least the law of conservation of energy would not be the issue at all).
Assumption 3: Both Causality and the law of conservation of energy holds outside of time
As far as we know, the law of conservation of energy requires the existence of time. It describes what is a possible change in the state of a system, and what is not. We do not know how change can be defined without the existence of time. If change could be defined outside of time, we don't know how the law of conservation of energy would be formulated, and whether it would hold.
Assumption 4: Anything that violates the law of conservation of energy is supernatural
Even if the first three assumptions were true, it would only show that the law of conservation of energy is not applicable to the moment of the Big Bang. That would be a limitation of the law, and would push scientists to refine the law, or to discover another theory that would be applicable. It would not show that the Big Bang cannot be explained by natural processes and phenomena.
Assumption 5: Anything "caused" by a supernatural process is created by an agent
Even if one was to somehow accept that the "universe came into existence by some supernatural process", there is no way to go from there to "the universe is created by an agent".
My Verdict:
Assumptions 1 through 3 are not substantiated by any evidence, assumption 4 is not only unsubstantiated, it is at least false in the case of virtual-particles, and assumption 5 is pretty much devoid of meaning. The argument is as weak as a simple assertion of a conclusion without any argument.