In June 2016, Neil deGrasse Tyson proposed (not entirely seriously, as this series of tweets should make obvious) the creation of a new country: Rationalia, governed by the dictum "All policy shall be based on the weight of evidence." To Tyson and the other citizens of Rationalia (including physicist Brian Greene, whose office I briefly occupied while mine was under construction this summer), this was obviously a good idea.
This kind of technocratic vision is, I think, appealing to many people in scientific professions, myself included (with some reservations). The most common objections to it were: (1) our values are to some extent axiomatic -- so the "weight of evidence" doesn't give us a way to resolve value conflicts, (2) states that describe themselves as rational have some pretty spectacular failure modes, and (3) expertise and evidence have limits beyond which we need other guides. I think all of these objections are pretty fair as arguments against a certain kind of Rationalia.
We already live in Rationalia
I'm not at all surprised that Tyson's proposal was met with a kind of gleeful disregard -- largely because he writes with the presumption that the reader will be charitable to his proposals, and likely considers (1-3) above to be so obvious as to be not worth remarking on (honestly, I feel the same way). Of course we should decide on "the Good" before trying to achieve it; of course we should avoid the smugly corrupt "science" that leads to phrenology, eugenics, and the guillotine. Of course we should be aware of the pitfalls of overconfidence and the limits of our knowledge, as well as more subtle epistemological boundaries.
What surprises me about the reaction to his proposal is that we already live in Rationalia. To a large extent, policy decisions are already made by experts in Washington. Agencies from the FDA to the EPA to the CBO constantly generate data and analysis for policy-makers. As I understand it, Tyson just wants to formalize this as a guiding principle of his republic (assuming, of course, that republicanism is supported by the weight of the data). And indeed, the rebuttals to his suggestion bear out this observation; much of the discussion of Rationalia does indeed use evidence, reasoning, and all that other good stuff.
Rather, I think what really turns off the critics of Rationalia is something else, which they call scientism, and indeed, this word shows up in a lot of the articles on Rationalia. I am more or less a believer in the universal applicability of (good) science, which is one of the more innocuous definitions of scientism. They're more worried about something a good deal less scientific.
There's a strain of scientism which I think is pretty pernicious, both to policy and to science itself:
I seriously doubt the 25 million fans of "I fucking love science" view science the same way I do: as the slow and careful accumulation of knowledge through experimentation, observation, cautious reasoning, and above all, skepticism. They're in it to learn some cool facts, find out why beer is actually good for them, watch cute animals, and have some of their political views confirmed. That's not even scientism, it's scientish. It's just co-opted the word "science" to describe the club. Of course, the educational goal of "I fucking love science" is laudable.
Where I think both Tyson and his critics agree is that the kind of booster scientism typified by "I fucking love science" is not a good template for policy-making. The kind of "science" that too often appears in public discourse is marked by both a deference to experts and a lot of motivated reasoning. Tyson's solution is a bit utopian:
But this is obviously a fine aspiration. I'm not sure what his critics' solution is -- after all, our current form of government places most policy decisions in the hands of experts who...weigh evidence.
One ludicrously entertaining form of Tyson's suggestion is implemented in this Quora answer:
Bouwman suggests that policy decisions should be made by a binary search through alternatives proposed by the population at large, with each choice in the search made by a large, randomly selected portion of the population. As more and more branches of the search tree are pruned, the remaining alternatives are given more and more scrutiny. It's a beautiful dream.
I think that Tyson's critics envision Rationalia as a degenerate form of Plato's republic, with Scientist kings ruling over masses of liberal arts majors. But there's no reason why Rationalia has to be so grim for the non-technical proletariat. After all, we already live right next door.