[This may become part of a book.]
What is truth? There are complicated ways of explaining “truth” that get all tangled up in questions about reality and perception, but we’re going to use a very simple one: truth is what makes the future less surprising.
No matter what you think you are and no matter what “reality” may be, the experience that you have to deal with (like every other human being) is of being thrown into a surrounding that does things independently of your thoughts. Shit happens, and you have to deal with it. The first step to dealing with it is to be able to predict it.
So, for example, if somebody says to you “It’s raining outside,” the meaning of that claim is a bundle of implied predictions, including “If you go outside without a hat, hood, or umbrella your head will get wet.” You test the truth of that claim by checking if those predictions are true. You don’t have to know what water “really is”, or for that matter what “reality” is. (We’ll get to what “reality” is later; it’s not actually very complicated when you start from here.)
All truth claims can be unpacked as predictions. Sometimes they’re predictions about obvious, directly observable events in our immediate environment (“Rain will make your head wet.”). Sometimes they’re predictions about events we can’t observe directly but which have consequences we can observe (“Electricity is a flow of electrons,” or “Genetic information is carried by DNA.”) Sometimes they’re predictions about the distribution of outcomes in repeated tests (“A flipped coin will fall heads-up half the time and tails-up half the time.)
Sometimes truth claims are predictions about states of mind in other people – but even these are tested by observable consequences. If I say “Cathy likes chocolate,” for example, you could check that claim by offering Cathy some and seeing if she smiles.
If anyone makes a “truth” claim at you that you can’t unpack into testable predictions, be careful. It may be that you don’t understand the claim but it’s still true – if you don’t know what the properties of an electron are, for example, you’re not going to get much meaning out of the truth claim “Electricity is a flow of electrons”.
But it may also be that the claim is meaningless. A classic example is the sentence “Green ideas sleep furiously.” How would you tell if this is true? What consequences could you check? You can only assign a meaning to this sentence if you can answer these questions.
A more concise way of putting it is that every truth claim corresponds to a set of experiments, not necessarily in the formal sense with test tubes and lab coats but in the informal way that we might stick a hand out a window to see if water falls on it.
And now we can say what “reality” is; it’s wherever the experiments happen. It’s whatever observables are accessible to us.
We can also say what “theory” is. A theory is just a machine for generating predictions. We judge the theory’s “truth” by whether those predictions are correct. And, remember, we make predictions because we need to cope with the shit that happens. A theory is a survival adaptation: we are theory-builders because we are prediction-needers because we are goal-seekers because we are survival machines.
All other distinctions, even those as basic as the one between “me” and “everything else”, are consequences of our need to theory-build so we can generate predictions so we can cope with the shit that happens.
Often, this theory-building has happened out of sight of our conscious minds. Some theories (like the one that there’s a “me”, and an “everything else”) are formed so early in life that by the time we learn to speak we’ve forgotten the process. Others, like the theory that reality consists of “objects” separated by “space”, are wired deep into the evolved structure of our nervous systems.
[Having got this far, we can start talking about mental models and perception and the map-territory distinction and ontology. The point is *not to try to do those first*; that way lies only confusion. And, BTW, good for you you if you recognized this as Peirce crossed with Heidegger with a dash of Husserl.]