The material presence of the work only serves as a conveyer launching an invitation to the observer to take part of the comprehensive game of the tho… - Antoni Tàpies

Everything takes place in an infinitely greater field than what is framed by the size of the picture or by what is materially in the picture. This matter [door/window/wall] is but a support inviting the viewer to participate in the much larger game of a thousand and one visions and feelings; it is the talisman lifting or sinking walls into the deepest recesses of our spirit, opening and at times closing windows in the construction of our impotence, our bondage, or our freedom. The 'subject-matter' then may be found in the picture or it may exist solely inside the spectator's head.

In: Tàpies, Werke auf Papier 1943 – 2003, Achim Sommer, Kunsthalle Emden, Altana 2004, p. 27

The most sensational surprise was the sudden discovery, one day, that my pictures, for the first time in history, had become walls. By means of what strange process had I arrived at such precise images? And why did they make me, their first viewer, quake with emotion?