It is a consistent trope of the literary intellectual over the ages that the quality of public discourse is declining. I find myself saying such things as I look over The Times every morning. But is it consequential? Does the quality of public discourse have any influence on the quality of decision-making? Is it purely epiphenomenal? Not quite, I think. The quality of public discourse has little effect on the quality of private decision-making. People are not stupid, and no matter what they say, will make their private decisions not on the basis of public discourse, but as they always have, on the basis of self-interest. Generally speaking, over time and over the entire population, they will make very good decisions.
In addition, one should never forget that poor public discourse may be perfectly adequate as a vehicle for excellent private decision-making, and indeed may for one reason and another create excellent circumstances for private individuals. For example, because the nonsense of public discourse may hamper the efforts of others, or simply create a niche, however temporary, in which a private individual can thrive.
But there is perhaps some ground for concern that when public decision-making is so large a part of decision-making overall, as it is at present, that the quality of public discourse does have a negative influence, since public decision makers will tend to make their decisions consistent with the prevailing discourse. In this respect they are no different from the private decision makers described above, and are attempting to camouflage the fact that public decisions are in fact taken to favour public decision-makers. It is best to seem in tune with the public. Of course civil servants will often represent this decision making to themselves as entirely responsible, and democratic, just as other private individuals will pretend to objectivity when serving their own ends. No matter; we know the truth in both cases from the outcomes of their decisions.
This suggests that the quality of public discourse only has a significant bearing on decisions taken in regard to matters of shared interest. Of course, notoriously, the extent of shared interest is unclear and contested, for obvious reasons. It seems, therefore, that we may never know whether poor public discourse is deadly or trivial, but judging from the actual behaviour of the people, there is a moderate concern that the sophistication of our culture is maintained, whereas we take a great deal of trouble over our own internal discourse and that of our families. That is perhaps one of the strongest indicators of the only moderate degree of common interest between individuals in general society.