“When, in the year 1913, in my desperate attempt to free art from the ballast of objectivity, I took refuge in the square form and exhibited a picture which consisted of nothing more than a black square on a white field...", said Kasimir Malevich when he first showed his Black Square at The Last Futurist Exhibition 0.10 in Petrograd (St. Petersburg) in December 1915. "This was no empty square which I had exhibited but rather the feeling of non-objectivity....The square = feeling
The white field = the void beyond this feeling."
This is a relatively precise definition by Malevich of what the black square, and the new concept of painting he developed from it – Suprematism (Lat. supremus, ‘highest’) – is meant to embody or evoke in the viewer: the feeling of non-objectivity and void. The exhibition sets out to explore a number of different aspects of Black Square.
Hamburger-Kunsthalle Web Site