Mountainous, Mousiest, Who?

I don't know what I am The dream from which I'm waking has left me in a trance A dissociated state kept separate from yesterday Where the immediate is all there is of me at all There is nothing here but me Neither bush nor building for as far as I can see And I struggle to discern without anything external Whether I might be a mountain or a mouse Still I feel I'm rather tall The dirt clouds at my feet do not reach my face at all And though I move through space, I do not so from my place And living things so often easily are moved The wind blows upon my mass Moving pieces of whatever might be fur and might be grass And in the feeling is revealed that I could not be made of rock Though I can only know what I myself might feel As I'm mostly gray and white From my features and my feelings I cannot easily decide And as it's by what I do that it's determined who I am And as I interact with nothing, so am I In fact, I can't think of a test That could once it was decided, lay uncertainty to rest Unless the context that I'm in be changed or understood again Then by proximity and history, I'll know