I take your point to be that I have taken something that is really a matter of degree "how much weight should I give to the opinion of this or that person?" and turned it into something dichotomous "is this person a good guide for me or not?" Here is my response.
Let's start by imagining that you can only hear the final opinions of the different advisers, and cannot discuss with them their arguments or evidence relating to the different elements of the question. In that case, the final opinion of anyone who has a valuable insight into any element of the question ought, all else equal, to move the needle for you at least a little bit. But it may be only a very little bit, and it can perfectly well be zero. In the Chicago School example, there are categories of firm conduct that Chicago people think should basically always be permitted, but that people like me think should sometimes be permitted and sometimes not. In those cases, merely knowing the final opinion of a Chicago person about a particular variety of conduct helps me not at all. Another way to get from "X's opinion should move you a very little bit" to "X's opinion should move you not at all" by throwing in a small fixed cost of the consultation.
But regardless of whether the adviser's final opinion moves you not at all or a little bit, the point is that there can still be a lot of value in hearing their arguments/evidence on particular points. If there are things that firms do that Chicago people think should always be permitted, but that people like me think should sometimes be permitted and sometimes not, the arguments/evidence of Chicago people on specific elements of the question might be of great value in helping me figure out which ones are which. And so the original point remains: the existence of valuable advisers who are not good guides.
I don't think this phenomenon is rare at all. I think in economics alone there are many insights in many fields that are now regarded to be extremely valuable for clarifying elements of big questions, but whose originators combined those insights with a great deal of wrongness, arrived at wrong final conclusions, and nevertheless were heeded on the final questions based on their insight into the specific elements.
I take your point to be that I have taken something that is really a matter of degree "how much weight should I give to the opinion of this or that person?" and turned it into something dichotomous "is this person a good guide for me or not?"
You have. To quote from your article:
...One kind of adviser is someone whose opinion, by your lights, constitutes strong evidence regarding the answer...But they are only providers of valuable input, not good guides. I think the distinction between these two types of advisers is often missed...Th
Haven't posted in quite a while.
Suppose you have a big, complicated question that you're not sure of the answer to, and you want to seek an adviser to guide you. One kind of adviser is someone whose opinion, by your lights, constitutes strong evidence regarding the answer; on the basis of that opinion alone you are prepared to substantially update your beliefs. Of course you may profit from further discussion beyond just hearing the adviser's opinion on the big question: since the question is complicated, hearing his or her reasoning or evidence on different elements of the big question may be valuable, but the point is that there are some advisers for whom just knowing their ultimate judgment moves the needle a lot for you. Such people might be termed "good guides."
But there may be other potential advisers whose ultimate opinion on the big question you don't credit much at all, but who you think might still have valuable insight into some important element of the question. A good example for me is "Chicago School" Industrial Organization Economics. It's members had some insights that are absolutely true and important ("one monopoly profit" and related ideas), and that the people who I would have regarded as my "good guides" had I been around at the time did not have before them. No analyst who does not understand those insights can be a good analyst, and no analysis that ignores them can be correct. But simply knowing what an orthodox Chicago School economist thinks about some big question would move me very little. They are a valuable part of my "intellectual portfolio" (to use a phrase favored by Brad DeLong) and I would be a fool to dismiss them. But they are only providers of valuable input, not good guides.
I think the distinction between these two types of advisers is often missed. If you believe my example (if not, substitute one of your own, the point of this post is not to debate IO), there are a bunch of expert economists (Chicago School types) who should have fancy prestigious professorships, and whose arguments should be given careful consideration; and there are another bunch of expert economists who should have fancy prestigious professorships, whose arguments should be given careful consideration, and whose advice should be heeded. Leave aside the practical difficulty of knowing which is which if you are, say, a reporter or a policy-maker. The point is that there should be two buckets for two different types of prestigious advice-giver, but we only really have one.