There were two major revolutions in scientific thought over the past 500 years according to the document. The first was the Scientific Revolution in the 17th-18th centuries which established experimentation and mathematical modeling as the basis for scientific knowledge. This led scientists to believe they could understand everything about the natural world. However, the 20th century saw four conceptual challenges emerge that demonstrated fundamental limits on what scientists can know. These included limits established by Lorenz, Cook and Turing, Godel, and Einstein and Heisenberg. Taken together, these ideas profoundly affected many disciplines by establishing limits on human knowledge.