Help with Liszt´s first transcendental etude

[rovis77]

Why does Liszt write with a double stem the sixteenth notes that start on measure 2 and end on measure 3?. Thanks!!

[klavieronin]

Liszt wants to show that there are three separate voices to play simultaneously; 1. the notes in the bottom staff, 2. the notes in the top staff with stems pointing downward, and 3. the notes in the top staff with the stems pointing upward. Try to imagine it as three separate instruments playing together.