"Conceptual artists are mystics rather than rationalists," Sol LeWitt wrote in his definitional text Sentences on Conceptual Art (1969). "They leap to conclusions that logic cannot reach." One mystical area of research with widespread impact during the 1960s and 1970s concerned invisibility and nothingness—concepts that photography, perhaps precisely because of its "rationalist" literalism, was often chosen to represent. Arte Povera, the Conceptual tendency with which Giovanni Anselmo, Gilberto Zorio, and the other Italian artists in this exhibition were affiliated, pursued the tension inherent in recording ineffable or prolonged experiences—awareness of the earth's rotation or an out-of-body passage—through the static and mechanical camera. Other artists approached such experiences with a mixture of irony and earnestness; Gordon Matta-Clark, who fried Polaroid photographs with gold-leaf flakes at his first gallery exhibition, took a genuine interest in alchemy, and Sigmar Polke was both serious and smiling in his assertion that "higher powers" had dictated his early photographic setups in the studio. An emerging environmental consciousness guided the philosophical reflections of Lothar Baumgarten, Agnes Denes, and Rudolf Sikora on humanity and the cosmos. Conceptual Art encouraged radically new thoughts about the human presence in the world, and the amenability of photography to multiple and changing incarnations made it especially well suited to realizing those thoughts.

_{Dennis Oppenheim. Stage 1 and 2. Reading Position for 2nd Degree Burn Long Island. N.Y. Materal... Solar Energy. Skin Exposure Time. 5 Hours June 1970, 1970. Dorothy and Herbert Vogel Collection.}