What does Human Dark Matter Mean to you?
(besides it being our namesake, considering scientifically and/or metaphysically)
The unseen that makes us (h/H)uman
Or is it
Speaking as the author who moonlights as a philosopher, The idea of the unseen yet essential cognitive and 'spiritual' (as relating a range of sensations from 'Gut feelings' to sensations of surreality) reactions working parallel to our known and understood dynamics of what it means to be Human, is what I would call the 'dark matter' of our being.