In the 19th century it was widely believed that scientific experiments on social issues were not, and never would be, feasible. Not only was social behaviour unpredictable in principle, but subjecting people to experimentation would be immoral. Although Comte, J. S. Mill, C. G. Lewis, and Herbert Spencer all argued to this conclusion, they also believed that natural innovations in society provided an adequate sub stitute for planned experiments. The question to be examined here is how such beliefs came to (...) be held and why they were never tested. (shrink)