One of my favorite ideas of championed by Karl Popper is what he calls the “truth is manifest” error. After describing how successful Renaissance epistemology (inspired by Bacon) was, he points out that it was…
…uncritical, and logically untenable. We can describe this radical and uncritical epistemological optimism of the Renaissance as the belief that truth is manifest. Truth may be hard to find. But once the truth stands revealed before us, it is impossible for us not to recognize it as truth. We cannot possibly mistake it. Thus nature is an open book. Or, as Descartes put it, God does not deceive us. …
The idea that truth is manifest is a philosophical idea (or perhaps even a religious idea) of the greatest historical importance. It is an optimistic idea, a beautiful and hopeful dream, a truly sublime idea. And I willing admit that there may be a grain of truth in it. But certainly not more than a grain. For the idea is mistaken. Again and again, even with quite simple things, we hold the truth in our hands and do not recognize it. And still more often we are convinced of having recognized the manifest truth while in fact we are entangled in errors.The Myth of the Framework, p. 202-203.
This idea is related to my previous post on how criticism usually unfolds. It means that it is not actually possible to know with certainty if an idea is refuted or not. Thus ideas aren’t “refuted or not refuted” as some suppose. 
Popper talks about the moral ramifications of falling into the Truth is Manifest error. Specifically, he claims that modern liberalism (the good kind) in Western Culture incorporated this error into it and that the end result was belief…
…that here exists a conspiracy against truth. For, it was argued, if so many do not see the manifest truth — that truth which is so clearly visible — it must be on account of false prejudices cunningly and systematically implanted into young impressionable minds so as to blind them to the truth.The Myth of the Framework, p. 205
Popper goes on to claim that this error became the basis for many good things (e.g. universal suffrage was created because ‘The People’ will recognize The Truth) but also all the “horrors of violent revolutions and civil wars” that followed. (p. 205). Popper elsewhere states this more strongly: “[The Truth is Manifest Error] is a case of a bad idea inspiring many good ones.” (Conjectures and Refutations, p. 11)  Nevertheless, Popper makes it clear that great evil comes from failing to understand that the truth is not manifest and thus hard to come by.
…we slowly [through our wars of religion and ideology] began to differentiate between sincerity and dogmatic stubbornness or laziness, and to recognize the great truth that truth is not manifest, not plainly visible to all who ardently want to see it, but hard to come by.Conjectures and Refutations, p. 504
Questions for Discussion:
- Critical Rationalists often take a stance that whatever is your best theory you should state boldly as truth. Is this consistent with not falling into the Truth is Manifest error? Why or why not?
- How is the Truth is Manifest error relevant to today’s political problems?
- How does this relate to our understanding of the “sincerity” of our political opponents?
- What “conspiracies against truth” do we reference or speak of today? Are they real or are they the truth is manifest error?
 I had a conversation with David on my previous post where he claimed otherwise. But upon further discussion, it would appear he might be less claiming we can tell with certainty if ideas are refuted or not (which would be the truth is manifest error) but rather that since you have to make up your own mind and no one else can for you that you effectively have to decide if in your mind an idea is refuted or not. This does not strike me as the truth is manifest error.
 Popper actually goes quite far here. He claims that the Renaissance fell into two errors. Those that believed the truth was hard to come by — so they turned to authority for answers — and those that optimistically believed the truth was manifest. He states that though he agrees more with the optimists (because he doesn’t believe in finding truth through authority) that the optimists were clearly epistemologically wrong since the truth is actually hard to come by. He goes on to say:
But I must admit, on the other hand, that the pessimists who feared the decline of authority and tradition were wise men. The terrible experience of the great religious wars, and the French and Russian revolutions, prove their wisdom and foresight.Conjectures and Refutations, p. 503
Though this is outside the purpose of this post, this is an example of the case for tradition and piecemeal reform.
The critical rationalist can appreciate traditions, for although he believes in truth, he does not believe that he himself is in certain possession of it.Conjectures and Refutations, p. 505