Many recent epistemologists have claimed to find inspiration in the discussion of knowledge and true belief in Plato’s Meno (97a-98a). At the same time, it has become common for philosophers to emphasize safety from error (or the like) as a necessary condition for knowledge – where (roughly) a belief is safe from error if and only if it held as a result of a process that could not easily yield a false belief.
Besides safety, another feature that a belief can have is what Robert Nozick called adherence to the truth – where (roughly) a belief adheres to the truth if and only if it is held as a result of a process that could not easily fail to yield belief if the proposition in question were true. As I shall argue, Plato’s Meno suggests that knowledge requires adherence – not that knowledge requires safety.
According to Meno (98a), the difference between knowledge and true belief consists in the fact that a mere true belief is like a slave who is liable to “run away from the soul”, whereas knowledge has somehow been more securely “tied down”. In effect, a mere true belief might too easily be lost, whereas knowledge is not so easily lost in this way. It is not suggested that if the true belief is lost it will be replaced by a false belief – the true belief might just simply disappear altogether, without being replaced by any belief on the relevant topic at all.
Plato’s suggestion here is presumably not that knowledge is less liable to be forgotten than a mere true belief. The suggestion is surely that knowledge is less liable to be rationally undermined by new evidence that comes to light. There are two ways in which new evidence might rationally undermine a true belief:
- The true belief might have been irrational or unjustified all along, and the new evidence might force the believer to realize that he never had any good reason for the belief in the first place.
- The true belief might originally have been rational and justified, but the new evidence might defeat that original justification.
Cases of this second kind (2) involve a JTB that falls short of knowledge. But they are not really like the original Gettier cases (or like Carl Ginet’s famous “barn façade” case). Instead, they are more like the “assassination case” that Gilbert Harman presented in Thought (1973, 143f.).
In Harman’s “assassination case”, there is a JTB that fails to count as knowledge, because there is a mass of (misleadingly) defeating evidence in the believer’s environment, and it is simply a fluke that the believer does not encounter this defeating evidence. But this defeating evidence – we may suppose – consists entirely of “undercutting” (rather than “rebutting”) defeaters. So if the thinker had encountered this defeating evidence, she would simply have given up on having any beliefs about the topic in question – she would not have come to believe the proposition’s negation. I.e., this belief fails to count as knowledge, not because it is unsafe, because it fails to adhere to the truth adequately.
In order to define ‘adherence to the truth’ more precisely, we need to factor the “process” that yields a belief into two components: the “positive conditions” (which require the presence of certain factors that normally yield the belief in question) and the “negative conditions” (which require the absence of certain factors that would inhibit the positive conditions from yielding the belief in question).
Then we can define the notion as follows:
A belief adheres to the truth iff, for some process P, the belief is held as a result of P, and in all nearby cases in which the believer meets the positive conditions of P, and the corresponding proposition is true, P yields belief in that proposition.
It is clear that a belief can be safe without adhering to the truth in this way. This will happen whenever there are no nearby cases in which the relevant process leads the believer to believe anything false, but there are nearby cases where the believer encounters undercutting defeaters (so that in those cases, the process fails to yield any belief at all).
In conversation, I have found that many fans of safety deny that knowledge requires this kind of adherence to the truth. In their view, the only way in which the “assassination case” can fail to be a case of knowledge is if it involves a failure of safety (as well as a failure of adherence). As I have argued here, in denying that knowledge requires adherence as well as safety, these philosophers are disagreeing with Plato’s Meno.