Is the universe determined by its initial conditions?

The question of free will can in principle be settled by answering the question of whether anything could turn out differently due to the act of a will which is not itself determined by prior events.
Allow me to pose the following thought experiment.

Suppose there was a “god” in the Deistic sense, who set everything in motion, and started the Big Bang. Suppose also that this being was somehow able to control the exact initial condition of the Big Bang. I am not sure if the uncertainty principle would apply in such a case, but for the moment assume that this being was not constrained by the uncertainty principle, and was able to determine the exact conditions of the Big Bang.

Would it be possible, in principle, for this being to determine every event which would happen in the future history of the universe? If quantum uncertainty would not allow for an exact prediction, would the being be able to determine the general course of events, such as knowing that intelligent life would arise on earth?

To put it another way, suppose we had two universes started by two Big Bangs, identical in every respect. Would the future histories of these universes be identical, assuming the same physical laws we observe in our universe apply in both identical universes?

If there was another universe that started with the exact initial conditions as ours, would another me exist, typing this identical thought in exactly the same sequence, etc?
Furthermore, assume that humanity develops to the point where it can create a Big Bang within our own universe. Would it be possible, in principle, to set the conditions of this event in such a way that an world would form which supported life, and on which intelligent beings would arise?

If we could do such a thing, we would be the gods of those beings!

Quantum Mechanics
Chaos Theory

All bets for prediction are off.

Things are not deterministic. On a large scale they look roughly deterministic, but small variations create large effects over time.

You couldn’t create a big bang as such within a universe - A ‘big bang’ isn’t an explosion, it’s an expansion of space time. It might be possible to create a ‘bubble universe’, connected to our own in some fashion with it’s own big bang. As to whether it would be possible in principle to set the conditions to give intelligent life? Om knows. I certainly couldn’t tell you - I don’t have the knowledge about the early universe to be able to answer that one, and I strongly suspect no human does.

Incidentally, bald is a haircolour. :wink:

Hey, it could have been a really lucky shot. God created luck, too, right?


Chekmate wrote:


Even if you could set both universes up with exactly the same initial conditions, all of which were measured with infinite precision, the inherent unpredictability of quantum mechanical behavior means that these two bubble universes would diverge from one another very, very rapidly.

Quantum mechanical events, you see, are not “predictable” in the usual sense. If we fire two electron through a very narrow slit in a wall, and then place a phosphoprescent screen some distance behind the slits to see where the electron went, those two electrons will not always end up at the same place on the screen, even if they both start out with exactly the same initial conditions (position, velocity, spin, etc.). We can only predict the probability that an electron will strike the phosphorescent screen at a given point. That’s the way quantum mechanics works.

Unless you are going to engineer some sort of “fatalistic” mechanism, by which God gets to determine the outcome of each quantum mechanical event for Herself, there is no way to predict how either of these bubble universes will evolve.

IANAP, but I do have some knowledge of the field. I’ll attempt to give an answer not constrained to any particular interpretation of quantum mechanics.

Quantum mechanical events may not be predictable in the “usual” sense, but the mathematics of the quantum mechanical wave equation itself is still perfectly deterministic. The difference is that this equation does not fix the outcome of some observation but instead gives the probabilities of all possible outcomes.

Because of the uncertainty principle, it is impossible in principle to know perfectly the state of the wave equation describing a system. But if somehow some entity (e.g. God) were to have perfect knowledge of the wave equation of the entire universe at some early time, s/he could conceivably have been able to calculate the precise probability that any later state would come into existence.

It’s arguable whether perfect knowledge of probabilities is enough to impair free will. I don’t have an opinion on the issue.

If the universe is materialistic I think we have to reject traditional notions of free will. In a materialistic universe everything from free will to consciousness is just the result of the sum of billions of uncaring, natural events.

If we accept traditional notions of free will does that necessitate accepting the existence of a non-material, supernatural element to the universe? Does this have any bearing on the existence of a deity (could an atheist believe in such a non-material realm)?

I have an irrational belief. Who’d’a thunk it?

I believe that the universe is deterministic. I’ve study quantum mechanics and I know all about uncertainty and chaotic systems and all that. But through it all I still believe that several levels down the universe must be deterministic. I think that things appear to be uncertain because we’re not looking deeply enough. What we now call one particle might actually be the complex interaction of trillions of particles. It might even be theoretically impossible that we should ever have access to the universe at that level. But I think that level is there. I can’t tell you why.
On another note, I don’t think that determinism and free will are incompatible. Look at it this way: One person looks at this chair I’m sitting in and says, that’s a chair. Another person could look at it and say, no it’s not. It’s just a collection of atoms. Here’s a carbon atom over here, and there’s a hydrogen atom over there, and they just happen to be in a configuration that seems to look like a chair when you put them together. I say, it doesn’t just seem to be a chair. It is a chair. The fact it’s made up of atoms doesn’t change that. One is a microscopic view. One is a macroscopic view. They’re both right. I see the same thing when I consider free will. Sure my brain is made up of neurons that are each following simple chemical laws, and even if they are acting deterministically (which I think they are) that doesn’t change the fact that I’m chosing my actions and therefore I have free will. Free will is a macroscopic view of things, and is just as valid as the microscopic view.

Neptune; you could abstract one level further and say that because of the way some people were taught and/or have their brains wired, there’s an N% possibility that someone looking at a chair will view it primarily as a whole, and another that they will look primarily at its makeup. You happen to fall within the N.