Intelligent design requires another proof of the origin of a creator. Or a proof the design changed at some point. Or a visit by the guy.
Multiverse only requires a proof of Matter/Antimatter interaction. If matter can be nullified then the sum of the universe is zero and that proves that there can be infinite Zero-Sum universes.
Your statement is kind of like saying since we can't prove the center of the sun is not made of Marshmallows the hypothesis that it is is as valid as a hypothesis that it is hyper-dense hydrogen in a state of fusion.
We can't go see, so they are both equally valid.
And then one day one of your kids (or anybody who wasn't there in general) would say :
"Intelligent design requires another proof of the origin of a creator. Or a proof the design changed at some point. Or a visit by the guy."
And you wouldn't have the slightest shred of a chance of convincing them (by your standard).
Furthermore I would say that early cosmology theories pretty blatantly point to the idea that the design changed at some point. That very statement made me think of inflation, which does sort of look like it might be a deity saying "whoops, let's just quickly change this for a while". Or at least, that's about as good an explanation for what happened as any other we have (suddenly the speed of light changed by a couple dozen orders of magnitude for a few milliseconds up to a few seconds, and then slowed down again. Without that change, the universe would not have formed). It is also known that the laws of nature today are not identical to the ones in force 10 billion years ago. So there were massive changes in the laws of nature early on, then subtler changes later.
(Also a pet peeve of mine : please stop using the word "multiverse" or "universes" it's a contradiction in itself. The whole point of having a word like "universe" is that it's everything, and that means only one. If there were multiple "universe" there would still be only one. Given the size of the visible universe, the chances are pretty fucking huge that it is in fact bigger than we will ever know, assuming Einstein is right, and that of course also means that the big bang theory is a load of crock, even when "corrected" by inflation. We just don't have anything better (yet ?))
It is known that the universe is not zero-sum, and that this is normal (which means that there is in fact no natural law of conservation of energy+matter either. We already knew that conservation of matter was flawed, since nuclear power, and that conservation of energy is also not happening. Now, thanks to the LHC we know it's possible to violate conservation of matter + energy too). We currently do not know of any law of conservation that is valid "in the large", no matter how solid they appear to be on our little blue ball down here.
The Eye is really complex how could it possibly have evolved with out Intelligent design? I'm told this lots of times. Here is a better one for those people. Why is water a universal solvent, non-flammable, buoyant as a solid floating in its liquid form, exist in all states of matter at in a range of temperatures we can live?
You know why eye's exist? Because Water Exists. If there is a universe where water doesn't float as Ice, the oceans would freeze solid killing all the macro life forms, we'd never evolve eyes, and the world would be limited to single celled organisms.
If gravity was 10% less strong than it is Earth would be farther from the sun, and too cold to live on.
The only observable universes are the ones where observers exist. That doesn't prove the existence of God, it proves the existence of man.
