The methods of science – with all its imperfections – can be used to improve social, political, and economic systems, and this is, I think , true no matter what criterion of improvement is adopted.
How is this possible if science is based on experiment? Humans are not electrons or laboratory rats. But every act of Congress, every Supreme Court decision, every Presidential National Security Directive, every change in the Prime Rate is an experiment. Every shift in economic policy, every increase or decrease in funding for Head Start, every toughening of criminal sentences is an experiment. Exchanging needles, making condoms freely available, or decriminalizing marijuana are all experiments. . .
In almost all of these cases, adequate control experiments are not performed, or variables are insufficiently separated. Nevertheless, to a certain and often useful degree, policy ideas can be tested.
The great waste would be to ignore the results of social experiments because they seem to be ideologically unpalatable. — Carl Sagan, The Demon-Haunted World p. 423.