I had a strange dream recently. I was at some sort of school carnival or fair, most of which took place in what looked like a high school or middle school gym, and there was a massive amount of food everywhere. However, things were complicated by the fact that there was a security robot that had a powerful death ray and I kept running foul of the robot. Why there was a military-grade, artificially intelligent robot capable of evaporating people in an instant doing security at a school fair never came up. I don't recall what it is I did first to attract its attention, but I then tried not to attract its attention, which made it even more suspicious of me. I tried all sorts of things, none of which worked. I woke up before I was evaporated by its death beam, but at various points a few chairs and other things went up in a burst of light, never to be seen again. The most surreal thing about the dream is that the dream was completely lacking in any anxiety or fear. I was at first a little irritated, then increasingly frustrated, as I could not shake the robot's suspicions, but even that was mostly quite mild. I just went through the school fair, enjoying doing school fair things and occasionally dodging or hiding from or trying to manipulate an artificial intelligence that was hunting me and could possibly annihilate me.
At one point in the dream, I tried to solve the problem by wrestling with the robot and rolling around the floor with it, like you would do with a dog. It did not work; the robot started hunting me even more relentlessly. Thinking about it in the waking world, this makes sense. If a dangerous robot were trying to hunt and kill you, and someone proposed that you solve the problem by rolling around on the floor with it, you would know that this would likely make things worse. But in the dream it did not make sense, and it was extremely frustrating that this unreasonable death-dealing robot was not placated by being shoved to the floor and rolled over and over in a good-natured tussle.
Nothing that happened in the dream truly happened in the real world. Indeed, if I said that something was "just a dream", you would know that I meant that it wasn't real. And yet if I were asked, "In a dream, did you in fact try to evade the death-ray robot?" it would be perfectly acceptable and reasonable for me to say that it was true, I did. We can recognize that something is true in dream even though it is not true in reality. Truth in reality is obviously in some sense 'more true' than truth in a dream. And yet, there's more to this, because we have to have some notion like 'truth in dream' if we are even to talk about 'truth in reality'. If say 'really true' or 'true in reality', this is contrastive. 'This is real' means, among other things, 'not merely dreamed', 'not merely imagined', 'not merely hallucinated', 'not something merely thought to be real', and so forth. By saying that it's rule, I am ruling out its being merely dreamed, and to do that I have to be able to compare what is dreamed with what is being called real. But for me to compare the two, there has to be something that is true in the dream that can be contrasted with what is real. If nothing were genuinely true in the dream, I could not say that the death-dealing robot from my dream did not really exist, because there would be no such thing as 'the' death-dealing robot from my dream; if you cannot have an accurate, i.e., adequately true, description of something, you can't successfully deny that it really exists. Truth in reality is known by ruling out things like 'merely true in a dream', and the 'true' in the latter case can't be a mere figure of speech for the comparison to give a coherent judgment about what is real. We get the same result if we say things like how it is true both in the dream and in reality that I have an interest in food; this can't be purely zeugmatic for the word 'reality' to mean anything here.
Thus we find that truth in reality is more properly truth than truth in a dream, that truth (in a dream) is not the same as truth (in the real world), and yet that truth in one case has to be comparable precisely as truth to truth in the other case. Being true in a dream is a different, less fundamental way of being true, than being true in reality. But, of course, there are many different 'ways of being true' in this sense: true in a dream, true in a fiction, true in a hallucination, true in a delusion, true in a model, true in an experiment, true in a possible world. And similar kinds of arguments can be run for each, because to say that something is true in reality is to say that it is not merely true in a dream and not merely true in a hallucination and not merely true in a delusion, etc., etc. There are different domains of truth, they are not all equally fundamental, and yet they are all domains of truth, related to each other as domains of truth.
We don't even have to stray very far abroad to get this result. Physicists work in at least three kinds of domains of truth -- 'true in a model', 'true in an experiment', and 'true in the physical world'. They run back and forth among these. It is true that they sometimes seem to conflate them. But they cannot be the same thing, because if you conflate 'true in a model' with 'true in the physical world', you not only get faleshoods, physics cannot even get off the ground, because then there's nothing actually to do with the model. If 'true in a model' and 'true in the physical world' were the same, your work would be done in just making the model; but we actually have to test our model by comparing and contrasting it with the physical world. As one of the many jokes about this goes, all models lie but some lie truthfully, and much of physics is about finding the truthful liars. Truth in a model cannot be the same as truth in the physical world; but to engage in physical inquiry using models requires being able to compare what's true in a model with what's true in the physical world; and the very nature of physical inquiry requires that 'true in the physical world' be more fundamentally true, in some way, than 'true in the model'. It's the same generic pattern. The same thing happens with 'true in an experiment', which has to mediate between 'true in a model' and 'true in the physical world', but can't reduce to 'true in a model' (because you actually have to do the experiment, not just make the model) or to 'true in the physical world' (because things can go wrong in an experiment that make it erroneous, so that what is true in the experiment does not fit what is true in the physical world).
I think there's a case to be argued that 'truth in a dream' is the first basic way we experience this analogy of truth; we learn the difference between dream and reality much earlier than we learn about such esoteric things as hallucinations, delusions, models, experiments, possible worlds, and so forth. The biggest rivals for this position are 'true in imagination' and 'true in fiction', but I think the circumstances of dreaming set it off more sharply and clearly from 'true in the real world' than we find with truth in imagination or in fiction. Truth in imagination and truth in fiction are subtler concepts. If that's the case, then if we had no dreams, it's possible that we might not really have any science or literature, either, not because the latter are just dreams, but because they are not -- without dreams, we might never have started learning how to contrast things with 'what is real', which both science and literature do. Perhaps it is even the case that we dream because, by contrast, it makes it easier to know the world, so that animals who dream are harder to fool. In any case, the comparison and contrast with dreaming plays an essential role in our understanding of reality and what it is to be real. Because we can think about what's true in dreams (and in fiction, and in imagination, and in a model, and so forth), we can think more easily and directly about what's true in reality.
