I’ll start by recapping a little about epistemic charity. The picture was that we can get some knowledge of other minds from reliable criterion-based rules. We become aware of the behaviour-and-circumstances B of an agent, and form the belief that they are in S, in virtue of a B-to-S rule we have acquired through nature or nuture. But this leaves a lot of what we think we ordinarily know about other minds unexplained (mental states that aren’t plausibly associated with specific criteria). Epistemic charity is a topic-specific rule (a holistic one) which takes us from the evidence acquired e.g. through criterion-based rules like the above, to belief and desire ascriptions. The case for some topic-specific rule will have to be made by pointing to problems with topic-neutral rules that might be thought to do the job (like IBE). Once that negative case is made we can haggle about the character of the subject-specific rule in question.
If we want to make the case that belief-attributions are warranted in the Plantingan sense, the central question will be whether (in worlds like our own, in application to the usual targets, and in normal circumstances) the rule of interpreting others via the charitable instruction to “maximize rationality” is a reliable one. That’s surely a contingent matter, but it might be true. But we shouldn’t assume that just because a rule like this is reliable in application to humans, that we can similarly extend it to other entities—animals and organizations and future general AI.
There’s also the option of defending epistemic charity as the way we ought to interpret others, without saying it leads to beliefs that are warranted in Plantinga’s sense. One way of doing that would be to emphasize and build on some of the pro-social aspects of charity. The idea is that we maximize our personal and collective interests by cooperating, and defaulting to charitable interpretation promotes cooperation. One could imagine charity being not very truth-conducive, and these points about its pragmatic benefits obtaining—especially if we each take advantage of others’ tendancy to charitably interpret us by hiding our flaws as best we can. Now, if we let this override clear evidence of stupidity or malignity, then the beneficial pro-social effects might be outweighed by constant disappointment as people fail to meet our confident expectations. So this may work best as a tie-breaking mechanism, where we maximize individual and collective interest by being as pro-social as possible under constraints of respecting clear evidence.
I think the strongest normative defence of epistemic charity will have to mix and match a bit. It maybe that some aspects of charitable interpretation (e.g. restricting the search space to “theories” of other minds of a certain style, e.g. broadly structurally rational) look tempting targets to defend as reliable, in application to creatures like us. But as we give the principles of interpretation-selection greater and greater optimism bias, they get harder to defend as reliable, and it’s more tempting to reach for a pragmatic defence.
All this was about epistemic charity, and is discussed in the context of flesh and blood creatures forming beliefs about other minds. There’s a different context in which principles of charity get discussed, and that’s in the metaphysics of belief and desire. The job in that case is to take a certain range of ground-floor facts about how an agent is disposed to act and the perceptual information available to them (and perhaps their feelings and emotions too) and then selecting the most reason-responsive interpretation of all those base-level facts. The following is then proposed as a real definition of what it is for an agent to believe that p or desire that q: it is for that belief or desire to be part of the selected interpretation.
Metaphysical charity says what it is for someone to believe or desire something in the first place, doesn’t make reference to any flesh and blood interpreter, and a fortiori doesn’t have its base facts confined to those to which flesh and blood interpreters have access. But the notable thing is that (at this level of abstract definition) it looks like principles of epistemic and metaphysical charity can be paired. Epistemic charity describes, inter alia, a function from a bunch of information about acts/intentions and perceivings to overall interpretations (or sets of interpretations, or credence distributions over sets of interpretations). It looks like you can generate a paired principle of metaphysical charity out of this by applying that function to a particular rich starting set: the totality of (actual and counterfactual) base truths about the intentions/perceivings of the target. (We’ll come back to slippage between the two on the way).
It’s no surprise, then, that advocates of metaphysical charity have often framed the theory in terms of what an “ideal interpreter” would judge. We imagine a super-human agent whose “evidence base” were the totality of base facts about our target, and ask what interpretation (or set of interpretations, or credences over sets of interpretations) they would come up with. An ideal interpeter implementing a maximize-rationality priciple of epistemic charity would pick out the interpretation which maximizes rationality with respect to the total base facts, which is exactly what metaphysical charity selected as the belief-and-desire fixing theory. (What happens if the ideal interpreter would deliver a set of interpretations, rather than a single? That’d correspond to a tweak on metaphysical charity where agreement among all selected interpretations suffices for determinate truth. What if it delivers a credence distribution over such a set? That’d correspond to a second tweak, where the degree of truth is fixed by the ideal interpreters’ credence).
You could derive metaphysical charity from epistemic charity by adding (some refinement of) an ideal-interpreter bridge principle: saying that what it is for an agent to believe that p/desire that q is for it to be the case that an ideal interpreter, with awareness of all and only a certain range of base facts, would attribute those attitudes to them. Granted this, and also the constraint that they any interpreter ought to conform to epistemic charity, anything we say about epistemic charity will induce a corresponding metaphysical charity. The reverse does not hold. It is perfectly consistent to endorse metaphysical charity, but think that epistemic charity is all wrong. But with this ideal-interpreter bridge set up, whatever we say about epistemic charity will carry direct implications for the metaphysics of mental content.
Now metaphysical charity relates to the reliability of epistemic charity in one very limited respect. Given metaphysical charity, epistemic charity is bound to be reliable in one very restricted range of cases: a hypothetical case where a flesh and blood interpreter has total relevant information about the base facts, and so exactly replicates the ideal interpreter counterfactuals about whom fixes the relevant facts. Now, these cases are pure fiction–they do not arise in the actual world. And they cannot be straightforwardly used as the basis for a more general reliability principle.
Here’s a recipe that illustrates this, that I owe to Ed Elliott. Suppose that our total information about x is Z, which leaves open the two total patterns of perceivings/intendings A and B. Ideal interpretation applied to A delivers interpretation 1, the same applied to B delivers interpretation 2. 1 is much more favourable than 2. Epistemic charity applied to limited information Z tells us to attribute 1. But there’s nothing in the ideal interpreter/metaphysical charity picture that tells us A/1 is more likely to come about than B/2.
On the other hand, consider the search-space restrictions—say to interpretations that make a creature rational, or rational-enough. If we have restricted the search space in this way for any interpreter, then we have an ex ante guarantee that whatever the ideal interpreter comes up with, it’ll be an interpretation within their search space, i.e. one that makes the target rational, or rational-enough. So constraints on the interpretive process will be self-vindicating, if we add metaphysical charity/ideal interpeter bridges to the package, though as we saw, maximizing aspects of the methodology will not be.
I think it’s very tempting for fans of epistemic charity to endorse metaphysical charity. It’s not at all clear to me whether fans of metaphysical charity should taken on the burden of defending epistemic charity. If they do, then the key question will be the normative status of any maximizing principles they embrace as part of the characterization of charity.
Let me just finish by emphasizing both the flexibility and the limits to this package deal. The flexibility comes because you can understand “maximize reasonableness within search-space X” or indeed “maximize G-ness within search-space X” in all sorts of ways, and the bulk of the above discussion will go through. That means we can approach epistemic charity by fine-tuning for the maximization principle that allows us the best chance of normative success. On the other hand, there are some approaches that are very difficult to square with metaphysical charity or ideal interpreters. I mentioned in the previous post a “projection” or “maximize similarity to one’s own psychology” principle, which has considerable prima facie attraction—after all, the idea that humans have quite similar psychologies looks like a decent potential starting point. It’ll be complex translating that into a principle of metaphysical charity. What psychology would the ideal interpreter have, similarity of which must be maximized?
Well, perhaps we can make this work: perhaps the ideal interpreter, being ideal, would be omnsicient and saintly? If so, perhaps this form of epistemic charity would predict a kind of knowledge-and-morality-maximization principle in the metaphysical limit. So this is a phenomenon worth noting: metaphysical knowledge-and-morality maximization could potentially be derived either from epistemic similarity-maximization or epistemic knowledge-and-morality maximization. The normative defences these epistemologies of other minds call for would be very different.