Representational art describes its subject matter by means of conventions that comprise a visual logic. In essence, every work of representational art constitutes an
illusion, as the three-dimensional world is reduced to a two-dimensional picture plane. Forms of representation can be manipulated to create contradictions or phrase visual questions, where illusions emerge from
deliberate discrepancies in the painting’s continuity. Contradictory visual perceptions are not easily comprehended simultaneously, one interpretation may be exchanged for another, but only one can be verified
at any one moment.
A new level of comprehension is reached when initially perceived information is transformed by the discovery of a concealed image. The viewer participates in the
process of organizing the new information into its various possible combinations. As, for example, in Salvidor Dali's 'Slave Market with Disappearing Bust of Voltaire', shown above. The head of Voltaire
and the two nuns have been subtly altered so that the perception of one depends upon the presence of the other. Although the figures are embedded within the same contour, it is difficult to experience them