In early 2009, the United States was engaged in an intense public debate over a proposed $800 billion stimulus bill designed to boost economic activity through government borrowing and spending. James Buchanan, Edward Prescott, Vernon Smith, and Gary Becker, all Nobel laureates in economics, argued that while the stimulus might be an important emergency measure, it would fail to improve economic performance. Nobel laureates Paul Krugman and Joseph Stiglitz, on the other hand, argued that the stimulus would improve the economy and indeed that it should be bigger. Fierce debates can be found in frontier areas of all the sciences, of course, but this was as if, on the night before the Apollo moon launch, half of the world’s Nobel laureates in physics were asserting that rockets couldn’t reach the moon and the other half were saying that they could. Prior to the launch of the stimulus program, the only thing that anyone could conclude with high confidence was that several Nobelists would be wrong about it.As Manzi goes on to note, even if we know with certainty that one group of Nobelists had to be wrong, we could never know with certainty which group it was because they could always point to uncontrolled variables that could have affected the outcome. There in lies a fundamental obstacle to advancing knowledge in the social sciences: the difficult of controlling the conditions in which predictions are tested. The situation has been improving in recent decades in fields such as Experimental Economics and Political Science , where randomized field trials and laboratory experiments have become more common. For example, the Workshop in Political Theory and Policy Analysis at Indiana University-Bloomington has a Working Group on Experimental Methods, comprised of faculty from various social-science disciplines focusing on the use and further development of experimental methods for both the field and the lab.
Will the social sciences ever be as "rigorous" as the so-called "hard" sciences? Perhaps not. But it's important to bear in mind that, even in biology, many theories including evolution by natural selection are not amenable to normal scientific methods of Popperian falsification. Moreover, certain fundamental "laws" of social science, such as the effects of changes in marginal supply and demand on price (in large, competitive markets), are at least as well-established scientifically as some aspects of quantum physics.