Yes, the more one looks into this business the more one muses, ‘who is the dreamer and who is the dreamed?’
It sometimes feels as though we are in a mirror or topsy turvy world, with things being the opposite of what they are made out to be; We are not the dreamer, but the dreamed! (Like the tip of some unknown iceberg)
In stranger moments, after reading about the bardo of becoming (after-life), I can almost wonder, ‘Heck! are we already there. Are we in the world of the dead and unaware; Running along ever decreasing circles, trapped in the habits and addictions of our previous lives.’
I think this ‘3d’ world is real when we are in it, just as the next world is real when we are ‘focussed’ on that. It is the focus and attention that dictates reality. (And of course having the ‘body’/vehicle to process that particular world is necessary)
I have the hunch that the next/astral world is more fundamental than our ‘3d’ reality; Our world is informed by and dreamed by it!
From our viewpoint though, in our physical bodies, the next world seems insubstantial and dreamlike. But i suspect from the viewpoint of that world, while inhabiting an ‘astral body’, our ‘material 3d world would appear similarly insubstantial and dreamlike.