On off-hand comments
The only thing remarkable here is Carnap's candor. We are surrounded by individuals making "definitive" judgments about matters that they know hardly anything about. In this particular instance, the recipient of the letter was Karl Popper, a friend and colleague of Hayek's, so that he could simply ignore the remark.
Most of us are not in that happy position. We cannot read (or view) more than a small portion of the cultural products that we feel we should. We therefore must rely to some extent on the judgments of others. A friend of mine, a fellow art historian, has formalized this tendency so that he has a kind of kitchen cabinet. From time to time he telephones these individuals, asking them to supply their latest judgments. Unfortunately, his expert on poetry was an academic versifier with an unfortunate tendency to commend his fellow academic poetasters. So my friend spent many hours pouring over useless junk. At least he followed up. But he remained perplexed about the purported targets of his admiration.
Granted that one must rely to some extent on the judgments of others, how can one protect oneself from adopting views that are inadequate or downright wrong? The first criterion that springs to mind is parti pris. Since many of the judgments offered on Fox News, for example, stem from biased "talking points" from the RNC and other dubious sources, one has to view everything stemming from that organization with suspicion. The same caveat is equally appropriate with regard to liberal and leftist organs, such as The New Republic and the Nation. Unfortunately, those alert to the biases of Fox News are less inclined to admit the distortions of those two newsmagazines, and vice versa.
Still, this recipe does not seem adequate. We cannot rely on those afflicted with terminal blandness, or on two-handed editorialist--those who state one position ("on the one hand"), following it immediately by the other ("on the other hand").
Nor is credentialing adequate. Many of the "experts" who pushed us into the Iraq war had escellent credentials. Those who rightly opposed it tended not to.
The only remedy I can see is what I would term sampling. As Sir Francis Bacon observed a long time ago, it is a fallacy that one must read every book all the way through, carefully annotating and pondering each point. In many cases, it is sufficient simply to dip into a book. I often open books at random just to get an impression. Having done this, one can turn to the index for some topic where one feels reasonably proficient. If the author doesn't measure up, then one can safely close the book.
My libary contains at least 20,000 volumes. I have no intention of reading all, or even most of them. But I have sampled them all. This is a much more satisfactory procedure than that of sampling wines, since one doesn't have to throw out the item lest it spoil. After all, there might be some reason for sampling the book again.
Most people do not have private libraries nowadays, and they do not visit research libraries. Yet quite a lot of people do hang out at Barnes and Noble, where they are (for the most part just sampling books).
Like everyone else I turn to the Internet nowadays. Yet I almost invariably find that if I want to produce a decent piece for my blog I must go also to printed sources. The combination of printed items with others gleaned from cyberspace is a good one, because each sphere serves as a check on the other.