Science Without Experiments
There are no black-and-white answers when we face integrated complexity.


Jim Manzi

The idea that that Republicans and conservatives are waging a “war on science” has become a staple of Democratic rhetoric. Hillary Clinton frequently referenced this in her campaign speeches. Chris Mooney, who wrote a book by this name, has an article on it in a recent issue of The New Republic. Daniel Engber has a three-part series on this topic in Slate. This idea has become widespread among liberals — and, unfortunately, many scientists.

Mooney’s thesis is that it’s all been downhill for the relationship between science and politicians since the “halcyon years” of the 1950s. His explanation for why this happened is sociological and political: Republican politicians and their supporters didn’t like the conclusions that some scientists reached, so they tried to stonewall or devalue the science. As I have written about at length, there is something to this. But Mooney, Engber, and others fail to consider an additional possible cause for the changed relationship between science and politics today versus 60 years ago: the kind of science used to inform public debates has changed.

One of the most famous (and probably apocryphal) stories in the history of science is that of Galileo dropping unequally weighted balls from the Tower of Pisa in order to demonstrate experimentally that, contra Aristotle, they would not fall at different rates. To the modern mind, this is definitive. Aristotle was one of the greatest geniuses in recorded history, and he had put forward seemingly airtight reasoning for why they should drop at different speeds. Almost every human intuitively feels, even today, that heavy objects fall faster than light ones. In everyday life, lighter objects will often fall more slowly than heavy ones because of differences in air resistance and other factors. Aristotle’s theory, then, combined evidence, intuition, logic, and authority. But when tested in a reasonably well-controlled experiment, the balls dropped at the same speed. Aristotle’s theory is false — case closed. This idea of the decisive experiment is not the totality of the scientific method, but it is an important part of it.

Now, we can very closely approximate the gravitational forces that govern the rate of descent of a ball applying Newtonian physics to the earth and the ball, while ignoring everything else. But this is only an approximation, since every object in the universe with mass actually exerts some gravitational attraction on both the earth and the ball. In part, this approximation works because gravitational force attenuates with distance by the inverse square law, so the force being exerted on the ball by, for example, the moon is comparatively tiny. These effects are so minute that scientists were able to demonstrate that Galileo’s finding was approximately valid — in fact, valid to within the measurement tolerance of available instruments — through all kinds of replicated experiments across Europe.

But suppose that gravity didn’t attenuate in this way, and if you let go of a ball it’s rate of descent might vary in all kinds of extraordinarily complex ways, the measurement of which exceeded the capacities of the best devices and computational facilities available in the world, because it mattered a lot exactly where you were versus every object with mass in the universe. There would be no way to isolate a component of the total system that had sufficient simplicity to allow us to conduct replicated experiments. We would be trapped by what we might call integrated complexity. If this were the case, Galileo might have had some perfectly true theory of gravity, but be unable to design an experiment with sufficient precision to “prove” that he was right (or more technically, show that his theory passed repeated falsification tests of the kind that Aristotle’s theory failed). He would be forced to do a funny kind of science: a science without experiments. We’d probably still be arguing about who was right.

The trend since the 1950s has been that policy-relevant science has become increasingly resistant to falsification testing, because it tends to address scientific questions of integrated complexity. In the introduction to his book, Mooney provides the following list of government entities as the places where the Republican war on science has been most severe: the Department of the Interior (focusing in the book on the Fish and Wildlife Service), the National Cancer Institute (focusing on the epidemiological debate about the purported abortionbreast cancer linkage), the CDC, FDA, EPA, and NOAA (focusing on global warming).