Sean Carroll

What is the ontology of that theory?

And someone might say, well, it's N point particles moving in three-dimensional space.

Someone else might say, actually, it's a single point in a 6n dimensional space.

That 6n dimensional space is the phase space for the whole system, the positions and velocities of every single particle.

I know that people actually do argue over which of those is a better description or more real or whatever.

To me, those are the same.

They're mathematically completely equivalent.

It's like saying, is Hamiltonian mechanics or Lagrangian mechanics real, right?

Or are numbers real when they're in base 10 or base 2?

It's just a translation from one point of view to another.

So I think that you have a fair point if you're worried that people who talk about these things, including myself, sometimes do it sloppily.

They say things without all the caveats attached to every single sentence or every single word in every single sentence.

But I think the meaning is clear.

People are arguing about, you know, what are the ingredients in your most fundamental description of the world?

And those ingredients are your ontology.

It would be very different in quantum mechanics than it would be in classical mechanics, that's for sure.

No, certainly not.

Like, I don't even think that perpetual motion machines are impossible as a matter of logic, right?

They're impossible as a matter of the laws of physics as we currently understand them.

That's true enough.