Reciprocity Whenever human activities incorporate machines or rigidly prescribed procedures, the modes of human interaction change. In general, technical arrangements reduce or eliminate reciprocity. Reciprocity is some manner of interactive give and take, a genuine communication among interacting parties. Ursula M. Franklin, The Real World of Technology reciprocity
The versatility of flat surfaces The versatility of flat surfaces is not commonly seen in nature. David Pye, The Nature and Aesthetics of Design Deep InterlockThe works of God