The traditional understanding of knowledge as “justified true belief” is internalist. That is to say, for a belief to count as an item of knowledge, it must actually be believed, and it must actually be true, and it must satisfy a third condition of being “justified”, which is understood as a state of mind. Justification is traditionally understood as being internal to the mind.
More recent “naturalized” epistemology is externalist. That is to say, for a true belief to count as an item of knowledge, it must satisfy a third condition of being connected in a special way to the real world “outside” the mind. There are various ways of characterizing this special connection: it must be reliable, it must “track” truth, it must be sustained by a law-like process, the belief in question must be non-accidentally true. I’ll use the word ‘reliable’. But whichever words we use for it, the connection reaches outside the mind, and so part of it is external to the mind.
I think these two ways of thinking about knowledge correspond to “is” and “ought” in an interesting way.
The internalist is looking for justification — and (in theory at least) he can check whether a belief is justified by examining the way it is linked to his other beliefs through relations of implication. Foundationalists think justified beliefs are implied by “basic” beliefs; coherentists think there is a network of mutual implication. Either way, these other beliefs are in the mind, and so they can potentially be put “before the mind” for inspection. According to this understanding of knowledge, we can have assurance that we know. In fact the main thrust of traditional epistemology is “doctrinal”: it’s aimed at assuring the radical sceptic that we do in fact have knowledge. We know something when a belief is justified, and it is justified or not as a matter of fact — an “is”.
Instead of seeking justification, the externalist wants reliability. And he isn’t “looking” for reliability so much as “hoping” for it. He can’t directly check whether the connection he hopes is reliable actually is reliable, because one end of it lies outside his mind. According to this understanding of knowledge, we can’t have an internal assurance that we know, because some aspects of knowledge are aspirational. We aspire to the goal of having reliably true beliefs. To the potential knower, such aspirations are better expressed by the word ‘ought’ than ‘is’. None of the beliefs he already has — as a matter of fact — can imply that these aspirations are met, because “oughts” cannot follow from “is”s alone.
This aspirational aspect of knowledge might be likened to “the object of the game” for a chess-player. The would-be knower and the chess player have goals: to have reliably true beliefs, and to get the opponent’s king into checkmate, respectively. These goals are the object of “oughts”: the would-be knower’s beliefs ought to be reliably true, and the player’s moves ought to bring the goal of checkmate closer. In both cases, the “ought” guides behavior in a nontrivial way.
Of course neither of these is a moral “ought”. Proper epistemic practice obliges us rationally rather than morally to aim for reliably true beliefs. Chess players’ implicit acceptance of the rules of chess — specifically, the rule that specifies the object of the game — obliges them to aim for checkmate. Someone who gets bored and plays “suicidal” chess to end a game quickly isn’t guilty of a moral failing, he’s just not playing chess properly.
The chess player has to interact with his opponent: he can’t focus on his own moves to the exclusion of his opponent’s moves. Analogously, the potential knower has to interact with the world: he can’t focus on his own beliefs to the exclusion of “answers” the world gives in response to the “questions” he “asks” it. In practice, this “questioning” of the world is the testing of hypotheses. To form new beliefs or new theories by simply building on what one already believes — including “data” — is like playing chess without paying attention to your opponent’s moves. In effect, this is what Bayesians do when they make epistemic decisons on the basis of “degrees of belief”. (I shall have more to say about Bayes’ Theorem in a forthcoming blog post.)
The “object of the game” of empirical knowledge is to transcend internal assurances and aim for reliably true beliefs — an external matter, which usually involves the testing of hypotheses.
I mentioned above that traditionally, epistemology was internalist. The tradition continues to this day, and it affects the way epistemology is taught in university philosophy courses: they tend to begin with Descartes’ Meditations, and typically don’t move very far beyond that. They tend to treat Gettier problems as a mere curiosity. Internalism can also affect the way scientists do science. Some sciences — especially those that appeal to “overwhelming evidence” to counter scepticism — use “internalist” methods of shaping models to fit “data” that may as well have been gathered beforehand. In effect, this is to eschew testing in favor of an internalist sense of assurance.
Proper science and knowledge are aimed at truth, not at assurance. Their aspirational aspects entail that testing is essential. To use another analogy: a miser might get assurance from counting coins he already owns, but he can’t make money unless he runs the risk of losing money by investing it in outside projects. In pursuit of truth rather than profit, science too must “cast its net” beyond “data” already gathered.