A couple of days ago, Buybuydandavis wrote the following on Less Wrong:
I'm increasingly of the opinion that truth as correspondence to reality is a minority orientation.
I've spent a lot of energy over the last couple of days trying to come to terms with the implications of this sentence. While it certainly corresponds with my own observations about many people, the thought that most humans simply reject correspondence to reality as the criterion for truth seems almost too outrageous to take seriously. If upon further reflection I end up truly believing this, it seems that it would be impossible for me to have a discussion about the nature of reality with the great majority of the human race. In other words, if I truly believed this, I would label most people as being too stupid to have a real discussion with.
However, this reaction seems like an instance of a failure mode described by Megan McArdle:
I’m always fascinated by the number of people who proudly build columns, tweets, blog posts or Facebook posts around the same core statement: “I don’t understand how anyone could (oppose legal abortion/support a carbon tax/sympathize with the Palestinians over the Israelis/want to privatize Social Security/insert your pet issue here)." It’s such an interesting statement, because it has three layers of meaning.
The first layer is the literal meaning of the words: I lack the knowledge and understanding to figure this out. But the second, intended meaning is the opposite: I am such a superior moral being that I cannot even imagine the cognitive errors or moral turpitude that could lead someone to such obviously wrong conclusions. And yet, the third, true meaning is actually more like the first: I lack the empathy, moral imagination or analytical skills to attempt even a basic understanding of the people who disagree with me
In short, “I’m stupid.” Something that few people would ever post so starkly on their Facebook feeds.
With this background, it seems important to improve my model of people who reject correspondence as the criterion for truth. The obvious first place to look is in academic philosophy. The primary challenger to correspondence theory is called “coherence theory”. If I understand correctly, coherence theory says that a statement is true iff it is logically consistent with “some specified set of sentences”
Coherence is obviously an important concept, which has valuable uses for example in formal systems. It does not capture my idea of what the word “truth” means, but that is purely a semantics issue. I would be willing to cede the word “truth” to the coherence camp if we agreed on a separate word we could use to mean “correspondence to reality”. However, my intuition is that they wouldn't let us to get away with this. I sense that there are people out there who genuinely object to the very idea of discussing whether a sentences correspond to reality.
So it seems I have a couple of options:
1. I can look for empirical evidence that buybuydandavis is wrong, ie that most people accept correspondence to reality as the criterion for truth
2. I can try to convince people to use some other word for correspondence to reality, so they have the necessary semantic machinery to have a real discussion about what reality is like
3. I can accept that most people are unable to have a discussion about the nature of reality
4. I can attempt to steelman the position that truth is something other than correspondence
Option 1 appears unlikely to be true. Option 2 seems unlikely to work. Option 3 seems very unattractive, because it would be very uncomfortable to have discussions that on the surface appear to be about the nature of reality, but which really are about something else, where the precise value of "something else" is unknown to me.
I would therefore be very interested in a steelman of non-correspondence concepts of truth. I think it would be important not only for me, but also for the rationalist community as a group, to get a more accurate model of how non-rationalists think about "truth"
I'd love to hear a more qualified academic philosopher discuss this, but I'll try. It's not that the other theories are intuitively appealing, it's that the correspondence theory of truth has a number of problems, such as the problem of induction.
Let's say the one day we create a complete simulation of a universe where the physics almost completely match ours, except some minor details, such as that some specific types of elementary particles, e.g. neutrinos are never allowed to appear. Suppose that there are scientists in the simulation, and they work out the Standard Model of their physics. The model presupposes existence of neutrinos, but their measurement devices are never going to interact with a neutrino. Is the statement "neutrinos exist" true or false from their point of view? I'd say that the answer is "does not matter". To turn the example around, can we be sure that aether does not exist? Under Bayesianism, every instance of scientists not observing aether increases our confidence. However we might be living in a simulation where the simulators have restricted all observations that could reveal the existence of aether. So it cannot be completely excluded that aether exists, but is unobservable. So the correspondence theory is forced to admit that "aether exists" has an unknown truth value. In contrast, a pragmatic theory of truth can simply say that anything that cannot, in principle, be observed by any means also does not exist, and be fine with that.
Ultimately, the correspondence theory presupposes a deep Platonism as it relies on the Platonic notion of Truth being "somewhere out there". It renders science vulnerable to problem of induction (which is not a real problem as far as real world is concerned) - it allows anyone to dismiss the scientific method off-handedly by saying that "yeah, but science cannot really arrive at the Truth - already David Hume proved so!"
We have somehow to deal with the possibility that everything we believe might turn out to be wrong (e.g. we are living in a simulation, and the real world has completely different laws of physics). Accepting correspondence theory means accepting that we are not capable of reaching truth, and that we are not even capable of knowing if we're moving in the direction of truth! (As our observations might give misleading results.) A kind of philosophical paralysis, which is solved by the pragmatic theory of truth.
There's also the problem that categories really do not exist in some strictly delineated sense; at least not in natural languages. For example consider the sentences in form "X is a horse". According to correspondence, a sentence from this set is true iff X is a horse. That seems to imply that X must be a mammal of genus Equus etc. - something with flesh and bones. However, one can point to a picture of a horse and say "this is a horse", and would not normally be considered lying. Wittgenstein's concept of family resemblance comes to rescue, but I suspect does not play nicely with the correspondence theory.
Finally, there's a problem with truth in formal systems. Some problems in some formal systems are known to be unsolvable; what is the truth value of statements that expand to such a problem? For example, consider the formula G (from Goedel's incompleteness theorem) expressed in Peano Arithmetic. Intuitively, G is true. Formally, it is possible to prove that assuming G is true does not lead to inconsistencies. To do that, we can provide a model of Peano Arithmetic using this standard interpretation. The standard set of integers is an example of such a model. However, it is also possible to construct nonstandard models of Peano Arithmetic extended with negation of G as an axiom. So assuming that negation of G is true also does not lead to contradictions. So we're back at the starting point - is G true? Goedel thought so, but he was a mathematical Platonist, and his views on this matter are largely discredited by now. Most do not believe that G has a truth value is some absolute sense.
This aspect together with Tarki's undefinability theorem suggest that is might not make sense to talk about unified mathematical Truth. Of course, formal systems are not the same as the real world, but the difficulty of formalizing truth in the former increases my suspicion of formalizations / axiomatic explanations relevant to in the latter.