Walter E. Williams asks
"Can we trust experts?" That question is not the right question to ask in the current circumstances. It's premature, because two other questions need to be answered first.
1) Is expertise in this area possible?
2) If it is, how would we know who the experts are?
Both of these are old problems. The first one is Socrates' problem. The second one is the one that concerned Plato in his later political writings, starting with
The Republic but also
The Laws.
There are fields in which expertise is demonstrably possible. In ancient Greece, this kind of expertise was called
techne -- the root of our word for 'technology.' It is a kind of craft knowledge, an ability to attain particular purposes. What Socrates wanted to know is whether those who claimed knowledge of things like the virtues could demonstrate their knowledge in the same way as shoemakers or shipwrights. It turns out that there isn't a clean break:
Still, by including commanding knowledge, the Visitor has left a middle ground between the purely theoretical and the practical. Certainly architecture is not practical since it does not directly produce anything, in the way carpentry does. However, it does give commands, whose effects are practical; thus, it is not for knowledge only, in the way in which calculation is for knowledge only. Insofar as architecture is an analogue for the political craft, the Visitor seems to be exploiting this middle ground[.]
Economics and politics would both like to think of themselves as possessing a kind of 'commanding knowledge,' akin to architecture. It is not clear that they do have this capacity, however, and we should insist that economists and politicians demonstrate a capacity for such knowledge before ceding to them any powers. We should certainly be ready to snatch away power from any of these so-called experts who prove to be incapable.
Even if that can be done, it still leaves the second problem. Let's say that economic expertise is possible, and that some small number of people really have it. How would I know who they are, if I don't have it myself? I can't judge directly because I lack the knowledge that I would need in order to recognize that they possessed it. I could trust the opinions of others who had the knowledge, but I have the same problem with identifying them. You are likely to end up exactly where we are, i.e., with a large class of mutually-reinforcing "experts" who affirm each other's claims to knowledge, but who really just agree with each other. If they're wrong, they are likely all wrong. Anyone they point to as another of their class is likely to be wrong too.
You might be able to judge from pragmatic experience, but that would require putting people in charge without being sure of their expertise (and, indeed, in spite of being told by all the experts that they were mad, fools, and the like). If they managed to produce good outcomes reliably over time, you could judge that they knew what they were doing.
I think we may be in the middle of such an experiment right now. It's a dangerous thing to do, but it may be the only way to discover expertise in the face of an established class of mutually-reinforcing pretenders to knowledge.