Truth.. and what you know

[MindForgedManacle]

You seem to be confusing existence with a particular type of existence. After all, it was never in question that Neo existed in the Matrix, only what the nature of that existence was (virtual).

I'm pretty sure that's what I just said.

The part where you said "Whether or not the apple and I 'really' exist...' threw me off I guess.

"given certain philosophical views" establishes a context. For example, given the philosophical view of physical monism, it is necessarily true that mind is a physical property.

Of course it does, I never denied it did.
However, that strictly speaking is not necessarily true. Property dualism is a physicalist-monist position, and yet it treats the mind as not being a physical property. :p

The problem occurs when a thick layer of reasoning is founded on a philosophical assumption, so that people lose sight of that original root. Then, inevitably, that massive construction is taken as sufficient proof to justify the assumption. But circles never work. NEVER, I say.

I think you're confused here. We all make certain assumptions on any number of topics. Outside of properly basic beliefs (stuff like reasoning's validity, generally our senses, existence of other minds, etc.), we take the pragmatic, coherent and evidenced beliefs which corroborate with our assumptions as supporting them. And that's because they do support them, and they are not circular. I believe the mind is basically an emergent property of the brain. The destruction or damaging of certain areas of the brain removing the agent's capacity to do some previously hekd ability is consistent and supportive of this type of view alone. Substance dualists have to contrive an entirely separate ontology to try and get in. Idealists' response basically devolves into solipsism.

So in other words, aside from a few beliefs, the basic ones, one's assumptions can generally be validated, and calling that circular is confusing.