ear of a whole generation. Hildebrand, too, challenged the 
     ideals of scientific naturalism by an appeal to the 
     psychology of perception: if we attempt to analyze our 
     mental images to discover their primary constituents, we 
     will find them composed of sense data derived from vision 
     and from memories of touch and movement. A sphere, for 
     instance, appears to the eye as a flat disk; it is touch 
     which informs us of the properties of space and form. Any 
     attempt on the part of the artist to eliminate this 
     knowledge is futile, for without it he would not perceive 
     the world at all. His task is, on the contrary, to 
     compensate for the absence of movement in his work by 
     clarifying his image and thus conveying not only visual 
     sensations but also those memories of touch which 
     enable us to reconstitute the three-dimensional form in 
     our minds.