‘There is a problem throughout the majority of my work: interior space, at the same time consequence and origin of positive exterior volumes. To define these interior spaces it is necessary to contain them, thus making them inaccessible to the spectator who is situated on the outside. Interior spaces, which have always been problematic for and interesting to architects, tend to be three-dimensional spaces defined by two- dimensional surfaces. I aspire to define the three-dimensional (hole) through the three-dimensional (plane) simultaneously establishing a type of correlation and dialogue between them. Thanks to these correlations, the exterior volumes to which we have easy access, will be our sure guide to come to know, at least in spirit, occult spaces.’
– Eduardo Chillida, undated note, Eduardo Chillida: Writings, trans. S. Ring and M. Faguet, Düsseldorf: Richter Verlag, 2009, p. 66-70.