Dream and dreamer

My life has been, of late, quite unexpected.
Although I should be growing old and hoary,
The mush my memory has now collected
Reminds of a strange, unsettling story.

A prince lay in his garden, and while lying,
Began to doze, and vivid dreams came to him.
He dreamt he was a butterfly, and flying
Was all he knew, as insecthood ran through him.

A long time passed. The butterfly was tiring;
It settled on a leaf. A cool breeze blowing
Set it to dream; or, sudden breath inspiring,
A prince awoke – and now, where was the knowing?

And so, my life. So many cold years settled,
And recent months with so much action teeming.
Why does this thought still sometimes get me nettled:
Which one is real, and which have I been dreaming?