> Reminds me of the Boltzmann Brain. If something is so unlikely, is it ok to assume it actually happened?

To begin with, we have the (weak) anthropic principle saying that no matter how improbable the event is, the fact that we are here and can observe it is proof that it has happened. We may doubt how to explain it, but we cannot deny that it exists just because it seems improbable.

Furthermore, we know that brains are a result of evolutionary refinement through thousands million years of entities competing with each other for survival to replicate their specific form among uncountable variations. We also know that the Big Bang was a extremely homogeneous concentration of immense energy at a single point. Allowing that we are comparing between infinitesimal probabilities, which one sounds like having less complexity and thus being more likely to be created by a single effect?

> If we say the current world was created by an eternal being with no cause, then we're not back where we started.

A flawless argument. But this argument cannot differentiate whether this "eternal being without a cause" is the universe itself or something external to the universe; it applies equally to both posibilites.

> If we don't know what caused the big bang, then I don't think we can say how similarly or differently other things will happen.

Right, that's a fair point of view. But my main point was that if we don't know the cause of a phenomenon and have no way to figure it out, any hypothesis about it is indistinguishable from fantasy. The principle of relativity is a heuristic to avoid fantasizing, and at the same time avoids the mistake of reasoning from the hubris of thinking that we are somewhat special among all the things in the known universe. Although there is no rational way to confirm this heuristic, the fact that it is simpler and requires less assumptions makes it preferable for me.

> When I look at this, and with your idea that we should interpret things to behave similar to what we know, it seems to me that since these elements of the universe have a cause, every element of the universe has a cause.

Yes, but that is a property of your observations about the events that take place within your reach, not an inherent property of the universe itself. Differentiating causes and effects are concepts that you choose to separate for the benefit of your understanding. It does not imply anything about how the physical world behaves. And it doesn't rule out the alternative of seeing the tree shape, DNA, proteins, molecules, particles and quantum waveforms as ways to look from different angles at the same ongoing process ("existence") which is the cause of itself, and that is exactly how I see it.

> On the other hand, isn't it possible that God created the universe so that it would end up being like this, with humans the way we are? And God might have wanted us to be like him in some ways (free will, the capacity to love).

See what I said above about fantasies impossible to confirm or reject, and about the arrogance of reasoning from the axiom that we are special. I see no difference between affirming that we are made in God's likeness and affirming that we have created God in our image; the net effect is the same, as we cannot ultimately disprove either of the two positions.

I believe Michael Ende expressed it in the best possible way: when humans enter the realm of fantasy and nurture it to create imaginary realms, we can have the best experiences possible for humanity; but when we try to bring those fantasies into our world and pass them off as realities, they become lies, which start the process of destroying both our world and the world of fiction.

I understand very well that the intimate belief in the existence of a being superior to us, who cares for us and is able to explain away all the doubts that may arise, has no rational basis and is therefore impossible to reject by reasoning, just as the belief that such a being does not exist has exactly the same lack of a rational basis; but at least our thinking can act to recognise this irresoluble problem as a child of thought, without any basis in any observation we can potentially make.