Wolfram87 wrote:
A curious mind might inquire "how would I know?".
And then might conclude that while each mind is subject to all manner of subjective distortions, sensing devices that record external events can be constructed and create a consistent picture of an external reality.
This could all be illusory, but there is no rational reason to believe it to be such, nor does the concept of illusion have any meaning without the premise of some non-illusory state. At some point, a curious mind might move on to other questions.
One might also wonder if this (including oneself) is not all a simulation and conclude that it might very well be, but if so it has the characteristics of reality, so it may as well be taken for real until some evidence of it not being real emerges. A feeling of dissociation from events and people is poor evidence against there being an external reality.
But even if one were to suppose that it is all a simulation or a dream, one has simply offset the notion of an underlying reality to a containing entity. There is a dreamer having the dream. Or a computer running the simulation.
Some sort of thing is thinking and therefore being.