Is the Moon There When No One's Looking at it?

Earlier this week I did a post featuring an interview with philosopher Bruce Gordon in which he explains the philosophical theory called idealism, and I'd like to continue with that interview today. In this segment Gordon talks about a couple of quantum mechanics' weird aspects.

Here's Gordon:

...in the quantum mechanical formulism, you can demonstrate that [a subatomic particle] has zero probability of existing in any bounded region of space, no matter how large. You can close various loopholes to make it kind of a rock solid result.

So what does that mean? It means that unobserved [particles] don’t exist anywhere in space, and thus have no existence apart from being observed. Interestingly enough, there have been experiments conducted that would support [this].

This means that subatomic particles do not actually exist apart from being observed by a mind. As idealist philosopher George Berkeley (1685-1753) put it, "To be is to be perceived."

Here’s another [example of quantum weirdness] that’s absolutely fascinating. It’s been dubbed the quantum Cheshire cat phenomenon. You may recall from the story of Alice in Wonderland that Alice observes this grinning Cheshire cat that then disappears, leaving only its grin. Alice remarks that she’s “Often seen a cat without a grin, but never a grin without a cat.”

Here's the Disney version:

Gordon continues:

In essence, that’s what’s going on [at the quantum level] because certain experiments — in particular, one using a neutron interferometer — have separated the properties of neutrons from any sort of substrate. So micro-physical properties don’t necessarily require a substrate.

What did the experiment do? Well, it sent the position of neutrons along one path and their spins along a separate path.

So that’d be kind of like sending a top along one path, and the fact that it was spinning along a separate path. Or the redness of an object along one path and the location of that object along another path. Micro-physical properties then can be separated from any idea of a substrate. They can be abstract properties moving through space.

So what do you get then? It would seem that under appropriate experimental conditions, quantum systems are decomposable into disembodied properties. A collection of Cheshire cat grins, if you will. So how is it that an abstract property could exist without any sort of substrate? Well, it can’t.

Unless, Gordon says, the property exists in a mental substrate, a mind, specifically, the mind of God.

There is no physical substrate, but the property has to inhere in something, so it’s inhering in the mind that perceives it. So in a way you could look at the properties, the quantum mechanical properties as kind of abstract particular properties, tropes even. But the tropes have to inhere in something. What they inhere in is a mental substance, not a physical one.

The interviewer, neuroscientist Michael Egnor, adds that,

What’s particularly fascinating as you point out, is how a deep look at the peculiarities, at the counterintuitive aspects of the quantum world, suggests that only an idealist metaphysics could make sense of all this. That materialist, or perhaps even dualist metaphysical perspectives fail at the quantum level. But the idealist perspective doesn’t.

The editor of the interview throws in this interesting tidbit:

Albert Einstein is reported to have asked his fellow physicist and friend Niels Bohr, one of the founding fathers of quantum mechanics, whether he realistically believed that "the moon does not exist if nobody is looking at it." To this Bohr replied that however hard he (Einstein) may try, he would not be able to prove that it does, thus giving the entire riddle the status of a kind of an infallible conjecture — one that cannot be either proved or disproved.

We can reasonably assume it exists, but we can never prove it without having a perception of some sort of it.

Berkeley's answer is that the moon does exist, even if we're not perceiving it, and that we can reasonably assume that it does, because it exists as an idea or perception in the mind of God. If God did not exist, however, we'd have no grounds for saying that the moon, or anything else, exists when no one was perceiving it.

The world, especially at the subatomic level, is a much stranger place than our common sense would have us believe.