[Almaviva]

> If there are elements of consciousness that are completely separate from the physical world (in that they have no effect on it), we cannot talk about them, nor even think about them.

Yet here we are, doing both, talking as well as thinking, right? If I talk about a universe where you'd never "woken up" as a subjective individual, and the present time was just like (to both of us) the previous 13.7 billion years, you know exactly the concept I mean, whether it's expressible in terms that have meaning beyond a single reader who knows (in the Cartesian sense) that their (subjective) existence is something special that only they can observe.

[shkkmo]

My speaking about my cartesian knowledge of my own subject experience is proof (to me) that my subject experience has physical effects.

If there are any properties that do not have physical effects, that makes them unspeakable, unknowable, and unthinkable. We can have a conceptual category for these properties, but we can't place anything in that category, not even from our own subjective experiences.

Type A Categories (that we can place things in):

Physical Causes & Effects: Our reality.

No Physical Causes but Physical Effect: True randomness

Type B Categories (that we can talk about but not place anything in):

Physical Causes but no Physical Effects: The Afterlife, The Future, Non-physical Elements of Consciousness

Neither Physical Causes nor Physical Effects: Completely separate realities

If we say that anything from Type B categories exists, then existence becomes a meaninglessly broad category. We can be wrong about whether something is Type B (say if we discover time travel), but nothing that is Type B exists.