
“A man never knows what a fool he is until he hears himself imitated by one.”
Quoted by Max Beerbohm in Hebert Beerbohm Tree: Some Memories of Him and of His Art Collected by Max Beerbohm http://books.google.com/books?id=wM08AAAAIAAJ&q="A+man+never+knows+what+a+fool+he+is+until+he+hears+himself+imitated+by+one"&pg=PA312#v=onepage (1920).