What would it mean to really understand or "explain" existence? Whatever it may mean, it must be something other than specifying a "cause" for existence. It must be something more like a way of "seeing that it must be so." What sorts of ideas and practices help put us in a frame of mind from which this kind of understanding is possible?
How are the concepts of "life" and "subjective experience" related? For example, can subjective experience exist in a system that is not alive? Answering this question requires clarifying our fundamental definitions of "life" and "subjective experience" or "consciousness" or "awareness."
Can we imagine a universe that is not "made out of" any fundamental substance at all? (Whether we label that substance "matter," or "mind," or something else that doesn't fit into the common categories of "stuff" that the universe might be fundamentally composed of.) What might it look like to describe existence in terms of a set of possible experiences, with what we call the "physical universe" and "laws of nature" emerging from some simple principles that prevent experiences from contradicting one another?
What's the essential insight at the heart of the so-called "hard problem of consciousness"? A few points are worth noting:
1) The core issue is not really an objective "problem" that exists "out there" in the world somehow. It's more like a description of a certain self-contradictory way of thinking: If you build a model universe out of concepts whose defining characteristic is the absence of experience, then no matter how you stretch and contort it, your model will not contain the property of experience. (See "Untangling the Hard Problem of Consciousness" for more on this point.) Given that we've created the contradiction by our way of thinking, the solution is to modify the concepts we use to describe reality, to avoid creating the contradiction.
2) If there is a real puzzle here at all, it has more to do with how things unfold over time. Was there a time when no experience existed, and then later a time when experience did exist? How did that transition occur? What underlying framework holds the relevant concepts for thinking about this?
3) A deeper underlying question that I think is more interesting and worthy of our attention is something like, "What properties must a universe have in order to implement meaning without internal contradiction, which requires both algorithmic and non-algorithmic aspects?"
Is existence possible without some kind of undifferentiated awareness? Or are existence and awareness inextricably tied together? (This is related to the interconnection of subject and object and George Greenstein's articulation "the only things that can be known are those compatible with the existence of knowers.")