In a recent essay, “Between Belief and Disbelief”, R. Feldman and E. Conee (F&C) defend the following evidentialist thesis:
(EC) Believing is the justified attitude when the person’s evidence on balance supports a proposition, disbelieving the justified attitude when the person’s evidence on balance supports the negation of a proposition, and suspension of judgement is the justified attitude when the person’s evidence on balance supports neither a proposition nor its negation.
F&C observe that (EC) “implies that even slight support is sufficient to make belief justified”(p. 76). In this respect, (EC) stands in contrast to views according to which an agent may be justified in suspending judgement about P even if their evidence slightly supports P over ¬P. F&C motivate (EC) with the following claim:
“Barely indicating truth is still indicating truth. Believing fits with this indication; withholding judgement does not. Thus, believing and not withholding is the attitude justified by minimal evidential support (p. 77).”
F&C go on to add the following two clarifications with respect to (EC):
First, they note that saying that having one’s evidence slightly support P over ¬P is enough to justify believing P is consistent with the idea that beliefs are accompanied by different strengths of conviction. Moreover, it is possible that beliefs themselves come in degrees, which correspond with the strength of conviction implicated by them. Given this fact, we may also hold that the strength of conviction with which an agent believes P (or their degree of belief in P) should mirror or be proportional to how much their evidence supports P. Hence, saying that having one’s evidence slightly support P over ¬P is sufficient for belief does not imply that it is sufficient for having full confidence in P or believing P with full conviction.
Second, they emphasize that just because one believes P, it does not follow that one ought to act on one’s belief. If one believes P with a very low level of conviction (or to a sufficiently minimal degree), it may be more appropriate to wait for additional evidence (assuming the option is available) rather than to act on one’s belief. These two points of clarification are meant to bolster the plausibility and palatability of (EC).
F&C do not go into great detail about what is entailed by an attitude being justified. They do note that “an attitude’s being epistemically justified does not imply having any sort of duty or obligation to take the attitude”(p. 79). However, it is plausible (and F&C would most certainly agree) that an attitude is justified only if it is rationally permissible. It also seems plausible that an attitude that is not justified is not rationally permissible. (Both of these claims are consistent with saying that an attitude being justified does not entail any rational obligation to adopt that attitude.) In sum, whether or not an attitude is justified appears to covary with whether or not it is rationally permissible, and not with whether or not it is rationally obligatory. In order to make the notion of justification a bit more concrete (and hence more amenable to appraisal), I will frame my discussion of justification in terms of whether or not an attitude is rationally permissible.
I wish to grant F&C’s contention that having one’s evidence on balance slightly support P is enough for it to be rationally permissible to believe P, given the caveat about strength of conviction or degrees of belief adumbrated above. However, I resist the implication that it would be rationally impermissible to suspend P if one’s evidence very slightly supported P over ¬P. This implication of (EC) seems particularly implausible in cases in which one is aware that the evidence currently available is known to be limited or incomplete. For example, suppose that the evidence we currently have available slightly supports the proposition “String Theory is true” over its negation. Suppose further that we know that the evidence bearing on whether or not String Theory is true is scarce or significantly incomplete. Under such circumstances, it seems as though it would be rationally permissible (i.e., justified) in suspending judgement about whether String Theory is true. If this is right, then one may be justified in suspending P even if one’s available evidence slightly supports P over ¬P.
To sum up, in cases in which we have reason to think that our currently available evidence is incomplete, we may be justified in suspending judgement even if on balance our evidence slightly favours P. If this is right, then it follows that (EC) is false.
Feldman, R. and E. Conee (2018). “Between Belief and Disbelief” in Believing in Accordance with the Evidence: New Essays on Evidentialism, edited by K. McCain. Synthese Library: Studies in Epistemology, Logic, Methodology and Philosophy of Science 398: 71-89.