This reads like a glorification of quantitative differences into a qualitative difference. Why reify this guide/portfolio distinction?
But simply knowing what an orthodox Chicago School economist thinks about some big question would move me very little.
And why is that?
Is that because they are literally as wrong as they are right, that they are competitive only with a random number generator/max-ent predictor? If they are, then that's a very peculiar sort of insight they are offering; why do you think you are free of the crippling biases that apparently reduce their otherwise insightful analyses to random noise?
Is it because they are only somewhat more right than wrong, but they do beat random guesses? Then knowing their opinion should move your decision somewhat. (Do they not move your decision at all? But we specified they were better than randomness, and so ignoring their opinion is throwing away some amount of information.) But then, they are also somewhat equivalent to your guide - but only somewhat.
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 an...
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.