[Filligree]

> But that is precisely how it is. Things that do not interact, do not exist.

What kind of predictive statement are you trying to make? How does the world change if your statement is correct, as opposed to false? What would be different?

[QuantumRoar]

The kind of predictive statements that all physicists are making for quite a while now and on which all of our technological progress is founded.

If there were some other fundamental means by which reality might be modified besides the basic interactions we know, our standard model of particle physics couldn't work so well, right? So to our knowledge, interaction is the one and only thing that puts a thing into existence or not.

As a side note: that is also the reason why WIMPs (weakly interacting massive particles) are a candidate for dark matter. The idea is that there might exist a form of matter that only interacts very weakly and thus it is incredibly hard to confirm its existence. Furthermore these WIMPs are massive (compared to other known elementary particles), so they might be out of reach of our particle accelerators.

These kinds of predictions follow from that.

[IanCal]

> If there were some other fundamental means by which reality might be modified besides the basic interactions we know, our standard model of particle physics couldn't work so well, right? So to our knowledge, interaction is the one and only thing that puts a thing into existence or not.

You're looking at this backwards, I think.

You claimed that a thing must interact in order to exist. If this is false then things exist but do not interact. Things which exist but do not interact with anything would not change anything we see in the world at all, and cannot in any way be tested for. The statement provides no predictions.

[QuantumRoar]

I see your point. What I meant was that existence and interaction are equivalent. But I see that I didn't express myself well there.

Let us presume that existence and interaction can be separate. Let us also assume for a moment that there is a definition of 'existence' without interaction. Then a reality with a thing that exists but doesn't interact is equivalent to a reality where this thing doesn't exist. If a thing's existence and non-existence yield equivalent realities, we can always assume that it does not exist. Therefore, we can set 'it interacts' and 'it exists' to be equivalent for all practical purposes.

That's my line of thought, which of course still doesn't exclude that things can 'exist' but not 'interact'. But if you would press me, I'd ask for a definition of the word 'existence' without using any form of interaction. I wouldn't know a proper answer to that.

[IanCal]

I think really this is leading into much more philosophical discussions. The practical viewpoint is I think 'anything that cannot interact with me can safely be ignored as irrelevant'.

But to push into a few thought experiments:

If I go into a room and it is sealed up so that nothing at all may escape and the room may never be opened, do I cease to exist? Or do you? Do we now have two realities? Is it possible to construct a setup where discrete realities no longer explain the true nature? Can I construct a system where two agents will disagree on where the boundaries are between these realities? Since we can create things where two parties cannot agree on the ordering of events, perhaps this could be extended to identify a setup and point in time where two parties would disagree on whether or not something exists (I'm really not sure on this, I feel the answer is no but then I think that about other things that smarter people than me can construct).

Do you consider only current technology or must we also consider things we don't yet know? When humanity was in its early stages, did one tribe not exist to the other? Did some countries not exist?

Do things "exist" if they don't currently interact, and may never interact, but possibly could?

The practical conclusion is perhaps that the term "exist" isn't very helpful.

[posterboy]

Corollary, things that do interact wouldn't necessarily exist, if he was wrong, I guess. At least that would be a nice proof by contradiction, but I can't draw that right now.

[jessaustin]

If philosophy admits the existence of entities that cannot be sensed (which, granted, many philosophers have done), it is opened to all sorts of metaphysical horseshit.

[JackFr]

I'll allow for the existence of your mind, for instance.

[jessaustin]

This is imprecise. You have some evidence of some HN-posting entity, because you see a post on HN. That's not the same as theorizing the existence of other, unseen, entities that could potentially post on HN but never will.

Perhaps you meant rather that you've given me a free pass on the Turing Test, or the equivalent for "dogs on the internet". Thanks, I guess, but I don't see what problems that solves, and anyway it's still about the nature of a sensed entity rather than the existence of an unsensed one.

[rebuilder]

I'm not who you were asking, but this seems to be along the line I've been thinking as well.

Disclaimer: I'm not trying to offend. If I do offend, please give me the benefit of the doubt and tell me why I'm mistaken.

The idea that interaction is key means there can be nothing supernatural. Everything that can cause an observable effect must do so by some natural means, and must therefore have some natural component to it as well. And if there is a natural component to something, then its interactions with that component must be via another natural component. Follow the reasoning and this precludes supernatural phenomena completely.

In brief, this is why I can't believe in any kind of deity, unless understood in the Clarkian sense of sufficiently advanced technology. I just haven't been able to see how the concept is not a logical fallacy.