Pen on printer paper.
 
Helen Keller is a great writer.  I see her as a meta-physical philosopher.  Her most famous book is her autobiography The Story of My Life (1902).  Her other books include The World I Live In (1908), Midstream: My Later Life (1929), Helen Keller's Journal (1938), and Let Us Have Faith (1940).  
 
"The best and most beautiful things in the world cannot be seen or even touched - they must be felt with the heart." - Helen Keller
 
Further reading:
 
https://www.gutenberg.org/files/2397/2397-h/2397-h.htm
 
https://en.wikipedia.org/wiki/Helen_Keller
 
https://npg.si.edu/learn/classroom-resource/helen-keller-1880%E2%80%931968