for us, there is no definitive way to prove that the current layer of dreaming, the layer in which we are typing this message to all of yall, is in fact layer 0, i.e "true" reality, because all possible reality checks can be simulated within higher layers of dreaming, up to and including higher layers of dreaming demonstrating that lower layers exist. What we are feeling right now, this "reality", feels no diferent to a "dream" state and so there is no possible way to prove this layer is the real one. to work around this, we have long since accepted that ther is and may not actually be a definitive layer 0, and that whatever layer we're in right now, we should treat as our local layer 0.