> Ah sorry I didn't mean to imply an association

I should have read your point more charitably, my bad :)

> This is perhaps true for metaphysical existence, but the ontological existence of a lion and the non-existence of an unicorn can absolutely be determined by the physical laws and the initial conditions of our universe

This may ve true, but irrelevant to my point. The 'laws of physics' are themselves one thing, and not another. It is logically possible to imagine a universe with anti-gravity instead of gravity (that is, where mass repels mass), or where natural processes were such that a lion's DNA ended up giving rise to a unicorn. It is equally logically possible to imagine a universe where unicorns pop in and out of existence, independently of any biological process. And infinite other possibilities. But this is not so. Your appeal to physical laws doesn't affect my point, which is not that we can know firstly about God's Willing, and secondly (and thereby) know about the existence of one and the non-existence of the other. Rather, it's that reality is certain particular things, and is not certain other particular things that it might logically have been. And this implies that certain concepts (lions, gravity) are willed into existence, and continue to be so willed here and now; and certain other concepts (anti-gravity, unicorns) are not.

The multiverse concept does not affect my point. If such a thing existed, there would be a Will that willed unicorns (and the supporting laws of physics/biology/etc) exist in the other universe, but not our one. This is unaffected by infinite multiverses. So the point stands.

>> You could describe the concept of anything in infinite detail without knowing whether that thing exists or existed.
> Yeah I read this, but not sure if I agree. That infinite detail would contain its history and details of its components, no?

I was careful to refer to the concept of lion/unicorn , which exists independently of how particular examples of said concept came to exist.

>> you wouldn't know from what I had told you which is real, which is historical and which is imaginary.
> This is obviously true. It is slightly amusing that this is then used to imply that God choose what things actually uexist, while I as a naturalist take it to mean we have to empirically look at the world to determine what exists.

These are not mutually contradictory. In any case, is it 'obviously true' or are you 'not sure if [you] agree' as you stated in your first reply? :-)

On a larger level, I don't think we can continue without discussing ontological reductionism. I can see that the PPC would make no sense if you think everything can be explained entirely in terms of its constituent atoms, which I think is your view. My own view is that the objects of our senses -- like pieces of wood, or apples, or dogs, or human beings -- cannot be reduced to the particles* that constitute them. To put it another way, what these things are is not the same as the particles they're made of. Nor is it the same as a particular arrangement of particles. "What a thing is" is a unity, and is distinct (though not separate) from the particles that compose it. This unity determines the particles' behavior -- or more generally, the whole determines the parts, not vice-versa. This also is true for an individual thing's properties, like color, ability to move, and (crucially) will.

If you think this is a useful line of enquiry, start kicking my view!

* Choose whatever level of particles you like: molecules, atoms, subatomic particles, quarks, etc. It doesn't affect the argument.