[…] I do believe that very many of the statements which we hold for truth are true. I also believe that very many statements which we hold for truth are false. And I do not believe that there is a criterion to distinguish with certainty between true statements and false statements. And this is the deepest reason for the fallibility of man. This does not mean that we shouldn’t try to find truth, and it does not mean that we shouldn’t get nearer and nearer to the truth. It doesn’t even mean that we cannot know that we have got nearer to the truth. We can know we have got nearer to the truth. But it means that we can never know that we have reached the truth.

Some followers of 20th-century philosopher Karl Popper take his philosophy of fallibilism too far. They think all of our ideas are necessarily false; that every idea contains some errors somewhere. For example, Kolya Wolf seems to think so (“Reason can neither generate true theories […]”), as does Brett Hall (“[W]e cannot ‘speak the truth’.”).

That’s not the case. People have discovered lots of true ideas. Meaning 100% true ideas – ideas without any errors. We just don’t know with certainty which ideas are true and which are false: there’s no criterion of truth, as Popper explains. So people are fallible. But we can know that we have made progress; that we have gotten nearer to the truth, as he says.

Popper opposes the two major but conflicting epistemologies of his (and still our!) time. One is a kind of epistemological authoritarianism: it says knowledge can only be genuine if it is certain or justified by some authority, eg a priest, a reputable philosopher, a science committee, a governmental body, our senses, ‘the book of nature’, or some mixture of any of these. The the entire purpose of epistemology (in their eyes), the primary problem epistemological authoritarians face (but will never succeed in solving), is: how do we guarantee that our knowledge is true? How do we justify our knowledge? Under this conception, true knowledge is considered ‘epistēmē’, as Popper explains (Conjectures and Refutations, ‘On the Sources of Knowledge and of Ignorance’).

The other major epistemology of Popper’s and our time – skepticism – correctly rejects this authoritarianism. But it does agree that such authority would theoretically be necessary for genuine knowledge to exist. Skeptics conclude that genuine knowledge is impossible.

Popper solves this false dichotomy and rediscovers what the Ancient Greek philosopher Xenophanes knew: that our knowledge is fallible opinion (‘doxa’, not ‘epistēmē’) and based on guesses. Progress consists not of justifying our theories to gain certainty, but of solving problems. Instead of asking how to guarantee that our knowledge is true, we ask how we can create the conditions necessary to correct errors. Error correction can and does lead us to truth. Xenophanes knew that we can speak “perfect truth”, although we’ll never know for sure whether we did so:

And even if by chance [man] were to utter
The perfect truth, he would himself not know it;
For all is but a woven web of guesses.

Contrast Xenophanes’ stance with the view of some of Popper’s fans who, again, think all of our statements must necessarily contain errors somewhere. Given the Popper quote at the beginning of this article, I think those ‘fans’ misrepresent Popper and twist his epistemology into a kind of cynicism. To be sure, they correctly reject authority. They also correctly reject skepticism: they don’t believe that our knowledge is any less genuine for not being endorsed by some alleged authority. But expecting all knowledge to be inherently flawed, ie never true, is a categorically negative view of knowledge and, by extension, of people and their abilities. This negativity is what makes proponents of this epistemology cynics.

(Note: I call this epistemology ‘cynicism’ due to its negative view of knowledge, but it shouldn’t be confused with the philosophy of cynicism.)

Logician Alfred Tarski’s correspondence theory of truth says truth is correspondence with the facts. So, given that some statement A corresponds to the facts – ie given that it is true – and you utter A, then you have spoken the truth. 100% the truth, with zero errors. Given that it is raining outside, and you say that it is, you have spoken the truth.

I’ll readily admit that the cynics’ view contains a grain of truth: we should expect many of our theories, even the best ones, to contain errors. And we should never stop looking for errors. If we ever stopped, we would cease being rational. It’s just that, again, cynics take fallibilism too far in thinking we cannot speak the truth.

If we could not speak the truth, our minds would have to have some subconscious mechanism that evaluates our ideas and detects and rejects true ones, or modifies them a bit to introduce errors, before we become aware of them. Otherwise, we could still utter the truth, if only “by chance”, as Xenophanes says. Such a mechanism would itself depend on a criterion of truth. So the epistemological cynics, though inspired by Popper’s fallibilism, and even though they would call themselves ‘fallibilists’, are not actually fallibilists. Whether they realize it or not, they rely on the existence of a criterion of truth and (simultaneously, ironically) reject the possibility that some of our knowledge is true.

Does the fact that some of our ideas are 100% true break with physicist David Deutsch’s notion that we can make unbounded progress? No. Although you can utter the truth in some area, there are infinitely many areas to explore, and there will always be more problems to solve.

Summary

Skeptical and authoritarian epistemologies are a mistake; they present a false dichotomy. Popper offered a third way: fallibilism. Some of his fans take fallibilism too far and turn it into what we might call epistemological cynicism. Such cynics think our knowledge is always wrong. In reality, we can and often do speak the truth – we just don’t know when.