For the past three thousand years epistemology has been about the truth, the whole truth, and nothing but the truth. Philosophers and scientists have continuously attempted to pinpoint the nature of truth, to find general logico-syntactic criteria for generating justified inferences, and to discover the true nature of reality. I happen to think that truth is overrated. And by that I don't mean that I'm a stereotypical postmodernist, prepared to say that all views are on equal footing (because after all, who can really say what's true and what isn't?). Instead I mean that I don't even think that the truth is a useful or coherent concept when stretched to accommodate what philosophers have tried to make it accommodate. It's not a malleable enough concept to have the generality that philosophers are asking of it. We need something else in its place.

A view similar to this is reservationism, which was first introduced^[1] by Moldbug in A Reservationist Epistemology. If you haven't read it, I suggest at least skimming it before reading the rest of this post, but the basic idea is that you can try to cram reason into an explicit General Theory of Reason for as long as you like, but at best it will always be a special case of "common sense." I have mixed feelings about Moldbug's post. On the one hand, it's delightfully witty and I agree with the general thrust of the argument. On the other hand, I think you can go a bit farther to explain his "common sense" notion than he lets on, and the abrasiveness and vagueness of his writing are likely to cloak some of the finer points. And despite giving (likely unintentional) hints about what we might replace "truth" with, he never does criticise the concept of truth, although he obviously criticises general theories of truth. 

Since I do depart from Moldbug, I'll call myself a pragmatist rather than a reservationist. I'll also give my pragmatism a slogan: "It's just a model."^[2] What's just a model? Bayesianism, falsificationism, positivism, naturalism, physicalism, panpsychism, quantum mechanics, operant conditioning, phlogistic chemistry, Catholicism, atheism, Hinduism, category theory, number theory, constructive analysis ... we could go all day with obvious examples. Here are some other examples: "Bayesian reasoners are optimal," "loop quantum gravity will give us a theory of everything," "a sentence is meaningful iff it, by itself or in conjunction with further premises, entails some observation statement not entailed by those other premises alone,"^[3] and more mundane examples like "It's raining outside," "My mother is 52," "Common sense," and "It's just a model." Here's another, an example central to my position: models are conceptual tools that help us think about some aspect of our experience and achieve our goals. I italicised "conceptual tools" because I want to emphasise their role as tools rather than their role as theories or propositions, and I want to emphasise the utility of model-tools rather than their truth. 

Lots of other models have been called pragmatism. Charles Peirce and William James came up with pragmatic "theories of truth." Richard Rorty and Ludwig Wittgenstein advanced pragmatic "theories of meaning." Instead of pragmatically explaining truth and related concepts, I'm giving it a rest. There are plenty of theories of truth already, and truth-focused epistemologies have their shortcomings. After all, what have the correspondence theory and Quinean naturalism given us in the philosophy of math except Platonism and confusion?^[4] Of course, these shortcomings shouldn't come as a surprise under the models-as-tools theory. Tools are built and tested with specific domains of application in mind by agents with limited imagination, and when we try to apply the tools to other domains we run the risk that they could be utterly worthless.

Of course, to provide a working alternative I need to convince others that it's worth trying, so let me try. Under this paradigm, where we judge models by their utility, there is no need to fret over whether the continuum hypothesis is "true" or not, whatever that might mean: we just note that as far as we can tell it's neither here nor there and move on.^[5] And suddenly the famous fact/value distinction looks very silly: of course facts^[6] inform us about how we should act; "facts" are just another model-tool in our system of model-tools, and the whole point of building our model-tools is to use them. These benefits should be enough to get your attention, at the very least. Another is that we don't have to use awkward, gross-feeling terms like "common sense." Common sense, in Moldbug's usage, is just the process that leads us to justify using models. So instead of common sense being the standard, we have our goals and instrumental rationality. Model building and model use are special cases of tool building and tool use, and agent-like goal-directed behaviour in general. 

My model is also compatible with the conception of rationality as winning. There is no holy reason juice in the universe^[7] that stops us from picking a winning but decidedly not reason-juice-flavoured strategy^[8]; the standard for picking a strategy is that it helps us achieve our goals, and strategies that make us sit in the corner don't pass. But my model is not compatible with the division between instrumental and epistemic rationality. Since the correspondence theory (and the map-territory metaphor) is just another tool in the toolbox, epistemic rationality is just a tool in the toolbox too, whereas instrumental rationality is the process we use to choose which tools we want to use and when (and why) we want to us them. In this model, instrumental rationality just is rationality, that "common sense" thing that Moldbug claimed subsumed everything else as a special case. 

And before I'm accused of being a relativist, let me say that not all tools are created equal, and we do have reason to use some in certain situations as opposed to others; namely, we have reason to use tools in certain situations when they produce outcomes we like better relative to other tools at our disposal. So when it comes to a models of physics, we use Aristotelian physics for simple everyday situations^[9], classical mechanics for many engineering projects and pedagogical functions, and quantum mechanics for many other engineering projects and current research.^[10] Now, often people will read this transition through different models as evidence for their favourite epistemology, and I won't disappoint you there: this transition shows us that as people began encountering new problems, old tools often didn't cut it. Go figure. After all, they weren't built with those future problems in mind, and foreseeing every possible roadblock that a tool could face would require another very powerful tool!

Which brings me to the problem of induction. Traditionally the problem is to find a general justification for the truth of universal claims on the basis of particular cases. We can translate this into my pragmatic framework fairly easily: construct the one tool to rule them all, a tool so awesome that we can use to achieve any achievable goal and that has provisions for any pesky roadblocks. The traditional statement reads easily as "carry out a foundationalist programme like Descartes," or in other words create a bedrock of certainty. It's generally agreed that this is impossible. My reformulation can be reread in a similar way: "carry out a reductionist programme like a theory of everything." Since the problem of induction is unsolvable, I strongly doubt that a reductionist theory of everything is on the menu. And if such a theory is ever announced I suspect the pragmatic slogan will still apply: It's just a model. A model with a fancy name, sure, but nonetheless with a limited domain of applicability and its own set of weaknesses.

That all having been said, my views aren't as alien to the general LW memecluster as you might expect. My position assumes consequentalism, and it's Quinean in that it's continuous with science rather than "prior" to it. I think that the results of science are some of the best tools we've developed, that physicalism is a good model for conceptualising and solving many problems, and that the correspondence theory of truth is a good tool in certain contexts. My goal here is not really to be a contrarian, as fun as that is. Rather, one of my goals is to find a better way to conceptualise a broader class of epistemological and scientific problems than current frameworks comfortably allow. 

If this post receives favourable feedback, I plan to write more posts expanding on these ideas. Specifically:

• The extent to which I am kind of sort of a relativist after all, but still not really.
• Foundational issues in math as seen through a pragmatic lens (potentially featuring a mysterious co-author).
• An epistemological analogue to the orthogonality thesis in ethics.
• The interface theory of perception and an evolutionary perspective on my model.
• The relationship between my pragmatism and probability theory. 
• Criticism and commentary on recent MIRI research.
• Criticism and commentary on key posts in the Sequences.

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[1] First introduced under that name, anyhow. For similar ideas, see Richard Rorty's Consequences of Pragmatism and Paul Feyerabend's Against Method.

[2] "My" is meant a bit loosely; I owe a lot to people I've discussed these ideas with, and to the reading material I've consumed. I'll elaborate on any of those contributions by request. 

[3] This is a paraphrase of A. J. Ayer from Language, Truth and Logic, Dover ed. pp. 38-39. 

[4] Quine gives us Platonism.

[5] It's been begrudgingly agreed that we can't decide on whether the continuum hypothesis is true since CH and its negation are independent of ZFC, but many people still argue about whether it is, ultimately, true or not. A pragmatic take on this debate is that since CH and ¬CH are both consistent with ZFC, we can strategically add either one of them as axioms for the purposes of making proofs easier if we like. 

[6] I doubt the usefulness and coherence of "fact" as much as I do "truth," but conventional language is conventional language. 

[7] "Universe" being another example of a model.

[8] Despite the arguments of champions of causal and evidential decision theories. 

[9] See Induction by Holland, Holyoak, et al., pp. 203-9 and 224-5, and A Function for Thought Experiments by Thomas Kuhn. 

[10] Obviously these are meant as examples of uses, not an exhaustive list.